PI3K-independent mTOR activation promotes lapatinib resistance and IAP expression that can be effectively reversed by mTOR and Hsp90 inhibition

Although HER2 targeted therapies have substantially improved outcomes in HER2 overexpressing (HER2+) breast cancer, resistance to these therapies remains a clinical challenge. To better understand the mechanisms of resistance to lapatinib, a HER2 and EGFR dual kinase inhibitor, we treated HER2+ breast cancer cells with lapatinib for an extended period to generate a lapatinib-resistant (LapR) cell line model and examined cancer-promoting signaling activation in LapR cells. We found that LapR cells possess enhanced mTOR activation, which was independent of PI3K and other known mTOR activators. Lapatinib resistance could be reversed by mTOR kinase inhibition. Intriguingly, LapR cells had constitutive cytosolic cytochrome C, indicating that LapR cells suppress lapatinib-induced apoptosis downstream of cytochrome C release from mitochondria into the cytosol rather than by preventing its release into the cytosol. Consistent with this notion, LapR cells possessed increased levels of 2 of the inhibitors of apoptosis (IAPs), survivin and c-IAP-2, which are reported to block caspase activation downstream of cytosolic cytochrome C release. Further, treatment with the mTOR kinase inhibitor AZD8055 or the Hsp90 inhibitor 17-AAG reversed expression of IAPs and overcame lapatinib resistance in LapR cells. Together, these data suggest that suppression of apoptosis downstream of cytosolic cytochrome C release, possibly through increased expression of IAPs or other caspase-suppressing proteins, may promote lapatinib resistance. Further, PI3K is thought to be the main driver of lapatinib resistance, but our findings indicate that PI3K inhibitors may be ineffective in some lapatinib-resistant HER2+ breast cancers with PI3K-independent activation of mTOR kinase, which may instead benefit from mTOR or Hsp90 inhibitors.     

A phase I pharmacokinetics study of lapatinib and tamoxifen in metastatic breast cancer (EORTC 10053 Lapatam study)

ObjectiveThis phase I study assessed the pharmacokinetic (PK), tolerability, safety and preliminary clinical activity of tamoxifen (T) and lapatinib (L) in patients with metastatic breast cancer (MBC).MethodsPatients (pts) with hormone receptor positive MBC, irrespective of HER-2 status, were randomly assigned to T → T + L group, tamoxifen in cycle 1 for 28 days then adding lapatinib on day 1 of cycle 2; or L → T + L group, lapatinib in cycle 1 for 14 days, then adding tamoxifen on day 1 of cycle 2 to evaluate the potential drug–drug PK interaction at steady-state. The dose of tamoxifen was 20 mg/day and lapatinib 1500 mg/day.ResultsTwenty-five pts were enrolled of which 23 started treatment, five (22%) of them were HER-2 positive. Median age was 59 years and 96% had PS ≤1. Eleven (91.7%) pts in the T → T + L group and 10 (76.9%) in L → T + L group received at least 2 cycles of treatment. The most frequently reported drug-related adverse events (>25% of patients) were diarrhoea (62%), anaemia (56%), rash (52%), fatigue (52%), dermatology other (34%) and leukopenia (28%). Grade 3–4 drug-related toxicities were infrequent (<10%). No cardiotoxicity was observed. T plasma concentrations did not appeared to be affected by the presence of lapatinib. L steady-state plasma concentrations were 20% lower after 28 days of co-administration with T. Eight (36.4%) patients experienced stable disease and median progression free survival was 2.7 months.ConclusionsThe combination of L and T was safe and clinically active. T affected L plasma concentrations, which remained within the therapeutic index.     

拉帕替尼与卡培他滨对HER-2阳性乳腺癌患者的疗效与安全性分析

目的探究拉帕替尼与卡培他滨对人类表皮生长因子受体(HER-2)阳性乳腺癌患者的疗效与安全性。方法选取42例HER-2阳性乳腺癌患者,随机数字法分为卡培他滨组(21例)和联合组(21例),所有患者均给予卡培他滨片进行治疗,联合组则在此基础上加用甲苯磺酸拉帕替尼片进行治疗。观察并比较两组疗效、中位疾病进展时间(TTP)、无疾病生存时间(PFS)、中枢神经系统(CNS)转移情况、肿瘤标志物水平及不良反应发生情况。结果联合组总体反应率、临床获益率、未发生CNS转移率分别为71.43%、85.71%、71.43%,高于卡培他滨组的38.10%、52.38%、38.10%(P<0.05)。联合组中位TTP、中位PFS均高于卡培他滨组(P<0.05)。联合组CNS转移率、总不良反应发生率分别为19.04%、47.62%,低于卡培他滨组的52.38%、80.95%(P<0.05)。治疗后,两组癌胚抗原(CEA)、卵巢癌相关抗原(CA125)、癌相关糖蛋白抗原(CA15-3)水平均降低,且联合组均低于卡培他滨组(P<0.05)。结论拉帕替尼与卡培他滨联合使用对HER-2阳性乳腺癌患者的临床疗效较高,可显著延长生存时间,降低肿瘤标志物水平及CNS转移发生的风险,安全性高,值得推广。     

A randomized phase II trial of trastuzumab plus capecitabine versus lapatinib plus capecitabine in patients with HER2-positive metastatic breast cancer previously treated with trastuzumab and taxanes: WJOG6110B/ELTOP

BackgroundFor human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) with progression on trastuzumab-based therapy, continuing trastuzumab beyond progression and switching to lapatinib combined with chemotherapy are both valid options. We conducted an open-label, randomized phase II trial to compare the efficacy of these strategies.Patients and methodsWomen with HER2-positive MBC previously treated with trastuzumab and taxanes were randomly assigned to receive trastuzumab plus capecitabine (HX) or lapatinib plus capecitabine (LX). The primary endpoint was progression-free survival (PFS) and the secondary endpoints included overall survival (OS) and the objective response rate (ORR). To explore the predictive value of the differential benefit of anti-HER2 drugs, PIK3CA mutations were assessed using circulating tumor DNA.ResultsEighty-six patients (43 in each arm) were enrolled. The median PFS was 6.1 months in the HX arm and 7.1 months in the LX arm (hazard ratio, 0.81; 90% CI, 0.55–1.21; p = 0.39); the median OS was 31.0 months in the HX arm and was not reached in the LX arm (hazard ratio, 0.58; 95% CI, 0.26–1.31; p = 0.18). The ORR was 40% in the HX arm and 41% in the LX arm. PIK3CA mutations were detected in 23% of the 35 analyzed patients, and in patients without PIK3CA mutations, LX yielded relatively longer PFS and OS than HX.ConclusionIn women with HER2-positive MBC previously treated with trastuzumab and taxanes, no significant differences in PFS and OS were observed between patients treated with LX and HX.Trial registration numberUMIN000005219.     

Therapeutic options for HER-2 positive breast cancer: Perspectives and future directions

During the last 15 years we have witnessed an unprecedented expansion in the drugs developed to target human epidermal growth factor receptor-2 (HER-2) positive breast cancer. Trastuzumab, pertuzumab, ado-trastuzumab emtansine and lapatinib are currently food and drug administration (FDA)-approved for the treatment of breast cancer patients with HER-2 over-expressed. However, given the amount of information gathered from years of uninterrupted clinical research, it is essential to have periodic updates that succinctly recapitulate what we have learnt over these last years and help us to apply that information in our daily practice. This review will pursue that objective. We will summarize the most relevant and updated information related to the state of the art management of HER-2 positive breast cancer in all the clinical scenarios including the adjuvant, neoadjuvant and metastatic settings. But we will also critically appraise that literature in order to highlight some key clinical concepts that should not be overlooked. Lastly, this review will also point out some of the most promising strategies that are currently being tested and may soon become available.     

The efficacy of lapatinib and capecitabine in HER-2 positive breast cancer with brain metastases: A systematic review and pooled analysis

IntroductionBreast cancer (BC) with HER-2/neu overexpression or amplification (HER-2+) is associated with a higher prevalence of brain metastases (BMs) when compared to other subtypes. Among approved drugs for HER-2+ BC, lapatinib (L) is associated with single agent activity toward BMs. We conducted a systematic review to determine the efficacy of L, singly or in combination with capecitabine (C), as a treatment for HER-2+ BMs.Material and methodsWe searched PubMed, EMBASE, The Cochrane Library, SCOPUS, Web of Science, ClinicalTrials.gov, World Health Organization International Clinical Trials Registry Platform (ICTRP), and the European Union Clinical Trials Register for studies reporting data on L, singly or in combination with C, for the treatment of HER-2+ BC with BMs. Primary end-points were overall response rate (ORR) and disease control rate (DCR); these were pooled to provide an aggregate value. Progression-free survival (PFS) and overall survival (OS) were secondary end-points. Data were pooled using number of events/number of evaluable patients, according to a fixed or random effect model.ResultsOverall, 12 studies were included in the present meta-analysis, for a total of 799 patients with BMs. The pooled overall response rate (ORR) was 21.4% (95% CI 11.7–35.9). After exclusion of patients that received L alone, ORR reached 29.2% (95% CI 18.5–42.7). The pooled median PFS and OS were 4.1 (95% CI 3.1–6.7) and 11.2 (95% CI 8.9–14.1) months, respectively.ConclusionsDue to its activity on BMs, the L + C combination may be considered for HER-2+ BC that has progressed in the brain, when local therapy has been performed or failed and re-irradiation is not feasible.     

Monitoring circulating epithelial tumour cells (CETC) to gauge therapy: in patients with disease progression after trastuzumab persisting CETC can be eliminated by combined lapatinib treatment

Background

In breast cancers, the gene for the growth factor receptor HER2 can be amplified leading to increased aggressiveness and metastasis formation. The monoclonal antibody trastuzumab prolongs relapse-free survival highly significantly but eventually many patients relapse.

Method

In this study, CETC were monitored using the Maintrac^® method during adjuvant trastuzumab treatment and during subsequent treatment with capecitabine/lapatinib.

Results

In one patient, trastuzumab led to marginal reduction in CETC with disease progress. The combination of capecitabine/lapatinib was preliminarily capable to eliminate all CETC, however, CETC reappeared. The second patient received adjuvant taxane together with trastuzumab and 1 year of further trastuzumab during which CETC increased. After stopping trastuzumab skin metastases occurred. Capecitabine/lapatinib led to complete CETC elimination with stable disease.

Conclusions

In patients with lack of CETC reduction in spite of trastuzumab treatment correlated with disease progression the combination of capecitabine/lapatinib highly efficiently led to rapid elimination of CETC warranting further monitoring during such studies.

     

A first synthesis of 18F‐radiolabeled lapatinib: a potential tracer for positron emission tomographic imaging of ErbB1/ErbB2 tyrosine kinase activity

Fluorine‐18‐labeled lapatinib has been successfully synthesized for the first time by the reaction of a dimethylformamide solution of meta‐[¹⁸F]fluorobenzylbromide with a Boc‐protected lapatinib precursor fragment. The reaction proceeded in the presence of K₂CO₃ at 110 °C for 10 min in a microwave and was followed by Boc‐group deprotection with trifluoroacetic acid. The overall radiochemical yield of the reaction starting from the radiofluorination of the iodonium salt was 8–12% (uncorrected, n = 6) in a 140‐min synthesis time.     

Lapatinib耐药性HER2阳性乳腺癌细胞株的建立及鉴定

目的:为研究HER2阳性乳腺癌细胞获得拉帕替尼耐药性的机制,建立稳定具有拉帕替尼耐药性的细胞株。方法:采用2μmol/L的拉帕替尼处理HER2阳性乳腺癌细胞BT-474,维持12个月,使细胞获得稳定耐药性。然后分别利用MTT、平板克隆和软琼脂克隆形成能力分析等方法,评价所建立耐药细胞的耐药能力。结果:所建立的耐药细胞在细胞增殖能力、平板克隆形成能力和软琼脂克隆形成能力等方面均具有耐药性。结论:建立的拉帕替尼耐药性细胞BT-474具有稳定的耐药性,为后续机制研究奠定基础。