Molecular evaluation of <Emphasis Type="Italic">PIK3CA</Emphasis> gene mutation in breast cancer: determination of frequency,distribution pattern and its association with clinicopathological findings in Indian patients

Somatic mutations in the PIK3CA gene are common in breast cancer and represent a clinically useful marker for prognosis and therapeutic target. Activating mutations in the PI3K p110 catalytic subunit (PIK3CA) have been identified in 18–40 % of breast carcinomas. In this study, we evaluated PIK3CA mutation in 185 Indian breast cancer patients by direct DNA sequencing. PIK3CA mutations were observed in 23.2 % (43/185) of breast tumor samples. PIK3CA mutations were more frequent exon 30 (76.8 %) than in exon 9 (23.2 %). Mutations were mostly clustered within two hotspot region between nucleotides 1624 and 1636 or between 3129 and 3140. Sequencing analysis revealed four different missense mutations at codon 542 and 545 (E542K, E545K, E545A and E545G) in the helical domain and two different amino acid substitutions at codon 1047 (H1047R and H1047L) in the kinase domain. None of the cases harbored concomitant mutations at multiple codons. PIK3CA mutations were more frequent in older patients, smaller size tumors, ductal carcinomas, grade II tumors, lymph node-positive tumors and non-DCIS tumors; however, none of the differences were significant. In addition, PIK3CA mutations were common in ER+, PR+ and HER2+ cases (30 %), and a comparatively low frequency were noted in triple-negative tumors (13.6 %). In conclusion, to our knowledge, this is the largest study to evaluate the PIK3CA mutation in Indian breast cancer patients. The frequency and distribution pattern of PIK3CA mutations is similar to global reports. Furthermore, identification of molecular markers has unique strengths and can provide insights into the pathogenic process of breast carcinomas.     

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.     

Low PTEN levels and <Emphasis Type="Italic">PIK3CA</Emphasis> mutations predict resistance to neoadjuvant lapatinib and trastuzumab without chemotherapy in patients with HER2 over-expressing breast cancer

Purpose

Aberrant activation of the PI3K pathway has been implicated in resistance to HER2-targeted therapy, but results of clinical trials are confounded by the co-administration of chemotherapy. We investigated the effect of perturbations of this pathway in breast cancers from patients treated with neoadjuvant anti-HER2-targeted therapy without chemotherapy.

Patients and methods

Baseline tumor samples from patients with HER2-positive breast cancer enrolled in TBCRC006 (NCT00548184), a 12-week neoadjuvant clinical trial with lapatinib plus trastuzumab [plus endocrine therapy for estrogen receptor (ER)-positive tumors], were assessed for PTEN status by immunohistochemistry and PIK3CA mutations by sequencing. Results were correlated with pathologic complete response (pCR).

Results

Of 64 evaluable patients, PTEN immunohistochemistry and PIK3CA mutation analysis were performed for 59 and 46 patients, respectively. PTEN status (dichotomized by H-score median) was correlated with pCR (32% in high PTEN vs. 9% in low PTEN, p = 0.04). PIK3CA mutations were identified in 14/46 tumors at baseline (30%) and did not correlate with ER or PTEN status. One patient whose tumor harbored a PIK3CA mutation achieved pCR (p = 0.14). When considered together (43 cases), 1/25 cases (4%) with a PIK3CA mutation and/or low PTEN expression levels had a pCR compared to 7/18 cases (39%) with wild-type PI3KCA and high PTEN expression levels (p = 0.006).

Conclusion

PI3K pathway activation is associated with resistance to lapatinib and trastuzumab in breast cancers, without chemotherapy. Further studies are warranted to investigate how to use these biomarkers to identify upfront patients who may respond to anti-HER2 alone, without chemotherapy.

     

PIK3CA mutations,phosphatase and tensin homolog,human epidermal growth factor receptor 2, and insulin-like growth factor 1 receptor and adjuvant tamoxifen resistance in postmenopausal breast cancer patients

Introduction

Inhibitors of the phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway can overcome endocrine resistance in estrogen receptor (ER) α-positive breast cancer, but companion diagnostics indicating PI3K/AKT/mTOR activation and consequently endocrine resistance are lacking. PIK3CA mutations frequently occur in ERα-positive breast cancer and result in PI3K/AKT/mTOR activation in vitro. Nevertheless, the prognostic and treatment-predictive value of these mutations in ERα-positive breast cancer is contradictive. We tested the clinical validity of PIK3CA mutations and other canonic pathway drivers to predict intrinsic resistance to adjuvant tamoxifen. In addition, we tested the association between these drivers and downstream activated proteins.

Methods

Primary tumors from 563 ERα-positive postmenopausal patients, randomized between adjuvant tamoxifen (1 to 3 years) versus observation were recollected. PIK3CA hotspot mutations in exon 9 and exon 20 were assessed with Sequenom Mass Spectometry. Immunohistochemistry was performed for human epidermal growth factor receptor 2 (HER2), phosphatase and tensin homolog (PTEN), and insulin-like growth factor 1 receptor (IGF-1R). We tested the association between these molecular alterations and downstream activated proteins (like phospho-protein kinase B (p-AKT), phospho-mammalian target of rapamycin (p-mTOR), p-ERK1/2, and p-p70S6K). Recurrence-free interval improvement with tamoxifen versus control was assessed according to the presence or absence of canonic pathway drivers, by using Cox proportional hazard models, including a test for interaction.

Results

PIK3CA mutations (both exon 9 and exon 20) were associated with low tumor grade. An enrichment of PIK3CA exon 20 mutations was observed in progesterone receptor- positive tumors. PIK3CA exon 20 mutations were not associated with downstream-activated proteins. No significant interaction between PIK3CA mutations or any of the other canonic pathway drivers and tamoxifen-treatment benefit was found.

Conclusion

PIK3CA mutations do not have clinical validity to predict intrinsic resistance to adjuvant tamoxifen and may therefore be unsuitable as companion diagnostic for PI3K/AKT/mTOR inhibitors in ERα- positive, postmenopausal, early breast cancer patients.     

Genetic deregulation of the PIK3CA oncogene in oral cancer

The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is one of the most commonly deregulated pathways in human cancers. PI3K comprises a catalytic (p110α) and regulatory subunit (p85), and p110α is encoded by the PIK3CA gene. Here, we summarize the known genetic alterations, including amplifications and mutations, of the PIK3CA oncogene in oral cancer. We discuss in detail PIK3CA mutations and their mutual exclusivity with pathway genes in addition to the incidence of PIK3CA mutations in relation to ethnicity. We describe the constitutive activation of PI3K signaling, oncogenicity, and the genetic deregulation of the PIK3CA gene and its association with oral cancer disease stage. We emphasize the importance of therapeutically targeting the genetically deregulated PIK3CA oncogene and its signaling. We also discuss the implications of targeting Akt and/or mTOR, which are the downstream effectors of PI3K that may possibly pave the way for molecular therapeutic targets for PIK3CA-driven oral carcinogenesis. Furthermore, this critical review provides a complete picture of the PIK3CA oncogene and its deregulation in oral cancer, which may facilitate early diagnosis and improve prognosis through personalized molecular targeted therapy in oral cancer.     

Direct inhibition of PI3K in combination with dual HER2 inhibitors is required for optimal antitumor activity in HER2+ breast cancer cells

Introduction

Despite multiple advances in the treatment of HER2+ breast cancers, resistance develops even to combinations of HER2 targeting agents. Inhibition of PI3K pathway signaling is critical for the efficacy of HER2 inhibitors. Activating mutations in PIK3CA can overlap with HER2 amplification and have been shown to confer resistance to HER2 inhibitors in preclinical studies.

Methods

Lapatinib-resistant cells were profiled for mutations in the PI3K pathway with the SNaPshot assay. Hotspot PIK3CA mutations were retrovirally transduced into HER2-amplified cells. The impact of PIK3CA mutations on the effect of HER2 and PI3K inhibitors was assayed by immunoblot, proliferation and apoptosis assays. Uncoupling of PI3K signaling from HER2 was investigated by ELISA for phosphoproteins in the HER2-PI3K signaling cascade. The combination of HER2 inhibitors with PI3K inhibition was studied in HER2-amplified xenograft models with wild-type or mutant PIK3CA.

Results

Here we describe the acquisition of a hotspot PIK3CA mutation in cells selected for resistance to the HER2 tyrosine kinase inhibitor lapatinib. We also show that the gain of function conferred by these PIK3CA mutations partially uncouples PI3K signaling from the HER2 receptor upstream. Drug resistance conferred by this uncoupling was overcome by blockade of PI3K with the pan-p110 inhibitor BKM120. In mice bearing HER2-amplified wild-type PIK3CA xenografts, dual HER2 targeting with trastuzumab and lapatinib resulted in tumor regression. The addition of a PI3K inhibitor further improved tumor regression and decreased tumor relapse after discontinuation of treatment. In a PIK3CA-mutant HER2+ xenograft, PI3K inhibition with BKM120 in combination with lapatinib and trastuzumab was required to achieve tumor regression.

Conclusion

These results suggest that the combination of PI3K inhibition with dual HER2 blockade is necessary to circumvent the resistance to HER2 inhibitors conferred by PIK3CA mutation and also provides benefit to HER2+ tumors with wild-type PIK3CA tumors.     

PI3K/Akt/mTOR inhibitors in breast cancer

Activation of the phosphoinositide 3 kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is common in breast cancer. There is preclinical data to support inhibition of the pathway, and phase I to III trials involving inhibitors of the pathway have been or are being conducted in solid tumors and breast cancer. Everolimus, an mTOR inhibitor, is currently approved for the treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. In this review, we summarise the efficacy and toxicity findings from the randomised clinical trials, with simplified guidelines on the management of potential adverse effects. Education of healthcare professionals and patients is critical for safety and compliance. While there is some clinical evidence of activity of mTOR inhibition in HR-positive and HER2-positive breast cancers, the benefits may be more pronounced in selected subsets rather than in the overall population. Further development of predictive biomarkers will be useful in the selection of patients who will benefit from inhibition of the PI3K/Akt/mTOR (PAM) pathway.KEYWORDS : Breast cancer, phosphoinositide 3 kinase (PI3K)/Akt/ mammalian target of rapamycin (mTOR), everolimus     

PI3K activation promotes resistance to eribulin in HER2-negative breast cancer

Background Eribulin is a microtubule-targeting agent approved for the treatment of advanced or metastatic breast cancer (BC) previously treated with anthracycline- and taxane-based regimens. PIK3CA mutation is associated with worse response to chemotherapy in oestrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2−) metastatic BC. We aimed to evaluate the role of phosphoinositide 3-kinase (PI3K)/AKT pathway mutations in eribulin resistance.Methods Resistance to eribulin was evaluated in HER2− BC cell lines and patient-derived tumour xenografts, and correlated with a mutation in the PI3K/AKT pathway.Results Eleven out of 23 HER2− BC xenografts treated with eribulin exhibited disease progression. No correlation with ER status was detected. Among the resistant models, 64% carried mutations in PIK3CA, PIK3R1 or AKT1, but only 17% among the sensitive xenografts (P = 0.036). We observed that eribulin treatment induced AKT phosphorylation in vitro and in patient tumours. In agreement, the addition of PI3K inhibitors reversed primary and acquired resistance to eribulin in xenograft models, regardless of the genetic alterations in PI3K/AKT pathway or ER status. Mechanistically, PI3K blockade reduced p21 levels likely enabling apoptosis, thus sensitising to eribulin treatment.Conclusions PI3K pathway activation induces primary resistance or early adaptation to eribulin, supporting the combination of PI3K inhibitors and eribulin for the treatment of HER2− BC patients.Subject terms: Breast cancer, Tumour biomarkers, Predictive markers, Cancer therapeutic resistance     

A gene expression signature of Retinoblastoma loss-of-function predicts resistance to neoadjuvant chemotherapy in ER-positive/HER2-positive breast cancer patients

Purpose

HER2-positive (HER2+) breast cancers show heterogeneous response to chemotherapy, with the ER-positive (ER+) subgroup deriving less benefit. Loss of retinoblastoma tumor suppressor gene (RB1) function has been suggested as a cardinal feature of breast cancers that are more sensitive to chemotherapy and conversely resistant to CDK4/6 inhibitors. We performed a retrospective analysis exploring RBsig, a gene signature of RB loss, as a potential predictive marker of response to neoadjuvant chemotherapy in ER+/HER2+ breast cancer patients.

Methods

We selected clinical trials of neoadjuvant chemotherapy?±?anti-HER2 therapy in HER2+ breast cancer patients with available information on gene expression data, hormone receptor status, and pathological complete response (pCR) rates. RBsig expression was computed in silico and correlated with pCR.

Results

Ten studies fulfilled the inclusion criteria and were included in the analysis (514 patients). Overall, of 211 ER+/HER2+ breast cancer patients, 49 achieved pCR (23%). The pCR rate following chemotherapy?±?anti-HER2 drugs in patients with RBsig low expression was significantly lower compared to patients with RBsig high expression (16% vs. 30%, respectively; Fisher’s exact test p?=?0.015). The area under the ROC curve (AUC) was 0.62 (p?=?0.005). In the 303 ER-negative (ER?)/HER2+ patients treated with chemotherapy?±?anti-HER2 drugs, the pCR rate was 43%. No correlation was found between RBsig expression and pCR rate in this group.

Conclusions

Low expression of RBsig identifies a subset of ER+/HER2+ patients with low pCR rates following neoadjuvant chemotherapy?±?anti-HER2 therapy. These patients may potentially be spared chemotherapy in favor of anti-HER2, endocrine therapy, and CDK 4/6 inhibitor combinations.

     

MYC-xing it up with PIK3CA mutation and resistance to PI3K inhibitors: summit of two giants in breast cancers

Approximately 35% of breast cancers exhibit PIK3CA activating mutation. Since PIK3CA hotspot mutation is the most frequently mutated gene in human breast cancers and primarily overlaps in HER2+ as well as ER+ breast cancers, the subset of patients bearing PIK3CA activating mutation does not get fullest benefit from either anti-HER2 or anti-hormonal agents. Literature also suggests that these patients may have chemotherapy resistance. Indeed, multiple clinical trials are currently evaluating the efficacy of over 30 drugs targeting different nodal points in the PI3K-AKT-mTOR pathway in breast and other cancers. However, to date, responses of solid tumors to PI3K pathway inhibitor monotherapy remains modest with an accompanied rapid emergences of drug resistance. MYC elevation represents one of the potential modes of actions by which breast tumors develop resistance to the PI3K pathway-specific targeted therapies. As products of oncogenes, both MYC and PIK3CA are well-established onco-proteins which contribute to breast oncogenesis. However, their similarities out number their dissimilarities in the context of their specific oncogenic cellular signals. In this review we will describe the specific cellular signals initiated following alteration in the MYC gene and PIK3CA gene in breast cancers. We will interrogate how MYC gene alterations influence the action of PI3K pathway targeted drugs in the context of PIK3CA mutation towards the development PI3K inhibitor induced drug-resistance in breast cancers.     

Association between gain-of-function mutations in PIK3CA and resistance to HER2-targeted agents in HER2-amplified breast cancer cell lines

BackgroundThe mechanism of resistance to human epidermal growth factor receptor 2 (HER2)-targeted agents has not been fully understood. We investigated the influence of PIK3CA mutations on sensitivity to HER2-targeted agents in naturally derived breast cancer cells.Materials and methodsWe examined the effects of Calbiochem (CL)-387,785, HER2 tyrosine kinase inhibitor, and trastuzumab on cell growth and HER2 signaling in eight breast cancer cell lines showing HER2 amplification and trastuzumab-conditioned BT474 (BT474-TR).ResultsFour cell lines with PIK3CA mutations (E545K and H1047R) were more resistant to trastuzumab than the remaining four without mutations (mean percentage of control with 10 μg/ml trastuzumab: 58% versus 92%; P = 0.010). While PIK3CA-mutant cells were more resistant to CL-387,785 than PIK3CA-wild-type cells (mean percentage of control with 1 μm CL-387,785: 21% versus 77%; P = 0.001), CL-387,785 retained activity against BT474-TR. Growth inhibition by trastuzumab and CL-387,785 was more closely correlated with changes in phosphorylation of S6K (correlation coefficient, 0.811) than those of HER2, Akt, or ERK1/2. Growth of most HER2-amplified cells was inhibited by LY294002, regardless of PIK3CA genotype.Conclusions:PIK3CA mutations are associated with resistance to HER2-targeted agents. PI3K inhibitors are potentially effective in overcoming trastuzumab resistance caused by PIK3CA mutations. S6K phosphorylation is a possibly useful pharmacodynamic marker in HER2-targeted therapy.     

Analysing the mutational status of PIK3CA in circulating tumor cells from metastatic breast cancer patients

The frequently altered phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway is involved in the regulation of cellular processes required for breast carcinogenesis. The aim of the project was to develop a method to identify hotspot mutations in the PIK3CA gene in circulating tumor cells (CTCs) of metastatic breast cancer (metBC) patients.From 44 enrolled CTC-positive metBC patients a total number of 57 peripheral blood samples were analysed by CellSearch^®. Genomic DNA of enriched CTCs was isolated, amplified and analyzed for PIK3CA mutations in exons 9 and 20 which lead to E542K, E545K or H1047R amino acid changes and result in increased PI3K activity. The mutations were detected by using SNaPshot-methodology comprising PCR amplification and single nucleotide primer extension.SNaPshot analysis was established using genomic DNA from different breast cancer cell lines and then successfully transferred to investigate blood samples and single cells. Overall, twelve hotspot mutations in either exon 9/E545K (6/12, 50%) or exon 20/H1047R (6/12, 50%) could be determined within 9 out of 57 (15.8%) blood samples from 7 out of 44 (15.9%) patients; CTC counts ranged from 1 to 9748. PIK3CA variants E542K, E545G and E545A were not detected.Analysing the PIK3CA genotype of CTCs has clinical relevance with respect to drug resistance, e.g. against HER2-targeted therapy. The herein described approach including SNaPshot technology provides a simple method to characterize hotspot mutations within CTCs enriched from peripheral blood and can be easily adopted for analysing further therapeutically relevant SNPs.     

Comparative efficacy and safety of CDK4/6 and PI3K/AKT/mTOR inhibitors in women with hormone receptor-positive,HER2-negative metastatic breast cancer: a systematic review and network meta-analysis

BackgroundCDK4/6 inhibitors and PI3K/AKT/mTOR inhibitors are both emerging agents for hormonal receptor (HR) positive and human epidermal growth factor receptor 2 (HER2) negative metastatic breast cancer. Evidence for the comparisons from head-to-head comparative trials is currently insufficient. This meta-analysis assessed the comparative efficacy and safety of these two groups of agents for HR+/HER2- metastatic breast cancer.MethodsSystematic searches of PubMed, Embase, CENTRAL, SciSearch between January 2010 to December 2019 were conducted. Randomized controlled trials (RCTs) which evaluated clinical benefits and toxicities of CDK4/6 inhibitors or PI3K/AKT/mTOR inhibitors plus endocrine therapy were adopted. Primary endpoints were progression-free survival (PFS) and overall survival (OS). Secondary endpoint was treatment-related adverse event (TRAE). Pooled hazard ratio (HR) and risk rate (RR) were used to assess the differences between CDK4/6 and PI3K/AKT/mTOR inhibitors.ResultsA total of twenty RCTs including 9771 participants were identified in this study. Pooled results showed that PFS was considerably prolonged by targeted therapy plus endocrine therapy. PFS was relatively better in CDK4/6 inhibitors than that of PI3K inhibitor group (HR, 1.43; 95%CrI, 1.12-1.61). Similar results were demonstrated in results after balancing lines of therapy or metastatic sites, both in viscera and bone-only. Coalesced outcomes revealed that CDK4/6 inhibitors plus endocrine therapy could significantly improve OS (HR, 0.78; 95%CrI, 0.65-0.94) than PI3K/mTOR inhibitors. Safety profiles of diarrhea and rash were consistent between CDK4/6 inhibitors and PI3K/AKT/mTOR inhibitors with no difference of estimated RR. Several TRAEs signified specificity, for instance, myelosuppression in CDK4/6 inhibitors or hyperglycemia in PI3K/mTOR inhibitors.ConclusionsClinical efficacy is in favor of CDK4/6 inhibitors, and safety profiles are comparable between CDK4/6 inhibitors or PI3K/AKT/mTOR inhibitors plus endocrine therapy.     

A portrait of germline mutation in Brazilian at-risk for hereditary breast cancer

Purpose

HER2?+?breast cancer (BC) is an aggressive subtype with high rates of brain metastases (BCBM). Two-thirds of HER2?+?BCBM demonstrate activation of the PI3K/mTOR pathway driving resistance to anti-HER2 therapy. This phase II study evaluated everolimus (E), a brain-permeable mTOR inhibitor, trastuzumab (T), and vinorelbine (V) in patients with HER2?+?BCBM.

Patients and methods

Eligible patients had progressive HER2?+?BCBM. The primary endpoint was intracranial response rate (RR); secondary objectives were CNS clinical benefit rate (CBR), extracranial RR, time to progression (TTP), overall survival (OS), and targeted sequencing of tumors from enrolled patients. A two-stage design distinguished intracranial RR of 5% versus 20%.

Results

32 patients were evaluable for toxicity, 26 for efficacy. Intracranial RR was 4% (1 PR). CNS CBR at 6 mos was 27%; at 3 mos 65%. Median intracranial TTP was 3.9 mos (95% CI 2.2–5). OS was 12.2 mos (95% CI 0.6–20.2). Grade 3–4 toxicities included neutropenia (41%), anemia (16%), and stomatitis (16%). Mutations in TP53 and PIK3CA were common in BCBM. Mutations in the PI3K/mTOR pathway were not associated with response. ERBB2 amplification was higher in BCBM compared to primary BC; ERBB2 amplification in the primary BC trended toward worse OS.

Conclusion

While intracranial RR to ETV was low in HER2?+?BCBM patients, one-third achieved CNS CBR; TTP/OS was similar to historical control. No new toxicity signals were observed. Further analysis of the genomic underpinnings of BCBM to identify tractable prognostic and/or predictive biomarkers is warranted. Clinical Trial: (NCT01305941).

     

The Gene Expression Status of the PI3K/AKT/mTOR Pathway in Gastric Cancer Tissues and Cell Lines

The PI3K/AKT/mTOR pathway plays a crucial role in the regulation of multiple cellular functions including cell growth, proliferation, metabolism and angiogenesis. Emerging evidence has shown that deregulation of this pathway has a role promoting gastric cancer (GC). The aim was to assess the expression of genes involved in this pathway by qPCR in 23 tumor and 23 non-tumor gastric mucosa samples from advanced GC patients, and in AGS, MKN28 and MKN45 gastric cancer cell lines. Results showed a slight overexpression of PIK3CA, PIK3CB, AKT1, MTOR, RPS6KB1, EIF4EBP1 and EIF4E genes, and a slightly decreased PTEN and TSC1 expression. In AGS, MKN28 and MKN45 cells a significant gene overexpression of PIK3CA, PIK3CB, AKT1, MTOR, RPS6KB1 and EIF4E, and a significant repression of PTEN gene expression were observed. Immunoblotting showed that PI3K-β, AKT, p-AKT, PTEN, mTOR, p-mTOR, P70S6K1, p-P70S6K1, 4E-BP1, p-4E-BP1, eIF4E and p-eIF4E proteins were present in cell lines at different levels, confirming activation of this pathway in vitro. This is the first time this extensive panel of 9 genes within PI3K/AKT/mTOR pathway has been studied in GC to clarify the biological role of this pathway in GC and develop new strategies for this malignancy.     

A combinatorial biomarker predicts pathologic complete response to neoadjuvant lapatinib and trastuzumab without chemotherapy in patients with HER2+ breast cancer

BackgroundHER2-positive (+) breast cancers, defined by HER2 overexpression and/or amplification, are often addicted to HER2 to maintain their malignant phenotype. Yet, some HER2+ tumors do not benefit from anti-HER2 therapy. We hypothesize that HER2 amplification levels and PI3K pathway activation are key determinants of response to HER2-targeted treatments without chemotherapy.Patients and methodsBaseline HER2+ tumors from patients treated with neoadjuvant lapatinib plus trastuzumab [with endocrine therapy for estrogen receptor (ER)+ tumors] in TBCRC006 (NCT00548184) were evaluated in a central laboratory for HER2 amplification by fluorescence in situ hybridization (FISH) (n = 56). HER2 copy number (CN) and FISH ratios, and PI3K pathway status, defined by PIK3CA mutations or PTEN levels by immunohistochemistry were available for 41 tumors. Results were correlated with pathologic complete response (pCR; no residual invasive tumor in breast).ResultsThirteen of the 56 patients (23%) achieved pCR. None of the 11 patients with HER2 ratio <4 and/or CN <10 achieved pCR, whereas 13/45 patients (29%) with HER2 ratio ≥4 and/or CN ≥10 attained pCR (P = 0.0513). Of the 18 patients with tumors expressing high PTEN or wild-type (WT) PIK3CA (intact PI3K pathway), 7 (39%) achieved pCR, compared with 1/23 (4%) with PI3K pathway alterations (P = 0.0133). Seven of the 16 patients (44%) with HER2 ratio ≥4 and intact PI3K pathway achieved pCR, whereas only 1/25 (4%) patients not meeting these criteria achieved pCR (P = 0.0031).ConclusionsOur findings suggest that there is a clinical subtype in breast cancer with high HER2 amplification and intact PI3K pathway that is especially sensitive to HER2-targeted therapies without chemotherapy. A combination of HER2 FISH ratio and PI3K pathway status warrants validation to identify patients who may be treated with HER2-targeted therapy without chemotherapy.     

Initiating breast cancer by <Emphasis Type="Italic">PIK3CA</Emphasis> mutation

PIK3CA mutations confer constitutive activation of PI3K, which initiates intracellular kinase signaling cascades that promote cell proliferation and survival. Recent studies by Meyer and colleagues, and Liu and colleagues demonstrate that expression of the H1047R exon 20 mutant of PIK3CA in luminal mammary epithelial cells induces tumorigenesis, implying that PIK3CA mutation is an early event in breast cancer. PIK3CA-H1047R-initiated tumors exhibit variable dependence on the oncogene and variable sensitivity to PI3K inhibition. Amplification of the oncogenes MYC and MET was observed in tumors that recurred following silencing of PIK3CA-H1047R, suggesting that these pathways represent mechanisms of escape from PI3K inhibition.     

PIK3CA mutations, PTEN, and pHER2 expression and impact on outcome in HER2-positive early-stage breast cancer patients treated with adjuvant chemotherapy and trastuzumab

BackgroundThis study was conducted to determine the frequency of PIK3CA mutations and human epidermal growth factor receptor-2 (HER2) phosphorylation status (pHER2-Tyr^1221/1222) and if PIK3CA, phosphatase and tensin homolog (PTEN), or pHER2 has an impact on outcome in HER2-positive early-stage breast cancer patients treated with adjuvant chemotherapy and trastuzumab.Patients and methodsTwo hundred and forty HER2-positive early-stage breast cancer patients receiving adjuvant treatment (cyclophosphamide 600 mg/m², epirubicin 60 mg/m², and fluorouracil 600 mg/m²) before administration of 1 year trastuzumab were assessable. PTEN and pHER2 expression were assessed by immunohistochemistry. PIK3CA mutations (exons 9 and 20) were determined by pyrosequencing.ResultsFive-year overall survival (OS) and invasive disease-free survival were 87.8% and 81.0%, respectively. Twenty-six percent of patients had a PIK3CA mutation, 24% were PTEN low, 45% pHER2 high, and 47% patients had increased PI3K pathway activation (PTEN low and/or PIK3CA mutation). No significant correlations were observed between the clinicopathological variables and PIK3CA, PTEN, and pHER2 status. In both univariate and multivariate analyses, patients with PIK3CA mutations or high PI3K pathway activity had a significant worse OS [multivariate: hazard ratio (HR) 2.14, 95% confidence interval (CI) 1.01–4.51, P = 0.046; and HR 2.35, 95% CI 1.10–5.04, P = 0.03].ConclusionPatients with PIK3CA mutations or increased PI3K pathway activity had a significantly poorer survival despite adequate treatment with adjuvant chemotherapy and trastuzumab.