Evidence of p38γ and p38δ involvement in cell transformation processes

The p38 mitogen-activated protein kinase (p38MAPK) signal transduction pathway is an important regulator of cell processes, whose deregulation leads to the development and progression of cancer. Defining the role of each p38MAPK family member in these processes has been difficult. To date, most studies of the p38MAPK pathways focused on function of the p38α isoform, which is widely considered to negatively regulate malignant transformation; nonetheless, few reports address the p38γ and p38δ isoforms. Here, we used embryonic fibroblasts derived from mice lacking p38γ or p38δ and show evidence that these isoforms participate in several processes involved in malignant transformation. We observed that lack of either p38γ or p38δ increased cell migration and metalloproteinase-2 secretion, whereas only p38δ deficiency impaired cell contact inhibition. In addition, lack of p38γ in K-Ras-transformed fibroblasts led to increased cell proliferation as well as tumorigenesis both in vitro and in vivo. Our results indicate that p38γ and p38δ have a role in the suppression of tumor development.     

HPV infection and p53 and p16 expression in esophageal cancer: are they prognostic factors?

Background

Esophageal squamous cell carcinoma (ESCC) is a highly lethal malignant tumor. Currently, Human papillomavirus (HPV) is suggested as a potential risk factor for esophageal cancer (EC) in addition to the classic risk factors, alcohol and tobacco, but this hypothesis still remains contradictory. We sought to investigate wether HPV and well-known biomarkers (p16 and p53) and patient-related factors that may have impact on survival of ESCC.

Methods

We conducted a prospective cohort study. By using multiplex PCR, we determined the prevalence of high risk HPV in ESCC, and evaluated the immunohistochemical expression of p16 and p53, molecular markers related to esophageal carcinogenesis in order to verify the potential influence of these variables in patients’s survival. Survival rates were estimated using Kaplan-Meier methods. A multivariate confirmatory model was performed using Cox proportional hazards regression.

Results

Twelve (13.8%) of 87 patients were HPV-DNA positive. Positive reactions of p16 and p53 were 10.7% and 68.6%, respectively. Kaplan-Meier analysis indicated that men (p = 0.025) had poor specific-cancer survival and a shorter progression-free survival (p = 0.050) as compared to women; III or IV clinical stage (p < 0.019) had poor specific-cancer survival and a shorter progression-free survival (p < 0.001) compared to I and II clinical stage; not submitted to surgery (<0.001) and not submitted to chemoradiotherapy (p = 0.039) had a poor specific-cancer survival, as well. The multivariate analysis showed that HPV, p16 and p53 status are not predictive parameters of progression-free and specific-cancer survival.

Conclusion

HPV infection and p53 and p16 expression are not prognostic factors in ESCC.

     

Are interactions with p63 and p73 involved in mutant p53 gain of oncogenic function?

Although still controversial, the presence of mutant p53 in cancer cells may result in more aggressive tumors and correspondingly worse outcomes. The means by which mutant p53 exerts such pro-oncogenic activity are currently under extensive investigation and different models have been proposed. We focus here on a proposed mechanism by which a subset of tumor-derived p53 mutants physically interact with p53 family members, p63 and p73, and negatively regulate their proapoptotic function. Both cell-based assays and knock-in mice expressing mutant forms of p53 support this model. As more than half of human tumors harbor mutant forms of p53 protein, approaches aimed at disrupting the pathological interactions among p53 family members might be of clinical value.     

HBME-1, CD15 and p53 Protein Expression in Thyroid Carcinoma and their Significance in Diagnosis

OBJECTIVE To investigate the protein expression of HBME-1, CD15 and p53 in thyroid carcinoma and in bengin thyroid diseases and to evaluate their value in diagnosis of thyroid disease. METHODS Sixty-one cases of thyroid carcinoma and 27 cases of different kinds of benign thyroid diseases were studied by immunohistochemical methods.RFSUTLS All cases of differentiated thyroid carcinoma were positive for HBME- 1,35.7% positive for CD15 and only 14.3% positive for p53. Twentyseven cases of benign thyroid lesions were absolutely negative for p53,7.4% of which were CD15 positive and 25.9% of which were HBME-1 positive. CONCLUSION HBME-1 and CD15 may be helpful to assist differential diagnosis of thyroid carcinoma from benign thyroid diseases.     

Bcl-2 and p53 immunoprofile in kaposi’s sarcoma

Seventy three cases of Kaposi's sarcoma (KS) from the 3 histological subtypes (patch, plaque and nodular) were assessed for bcl-2 and p53 protein expression. The aim was to determine the level of expression of these proteins in KS and in the different subtypes. Commercially available antibodies to bcl-2 and p53 were applied after both microwave and pressure cooking antigen retrieval. Bcl-2 immunoexpression increased from the patch stage (36%) to the plaque stage (45%) to the nodular stage (70.83%). Better immunostaining for bcl-2 was obtained after pressure cooking. p53 on the other hand, was not expressed in the patch or plaque stages, but 54.16% of cases in the nodular stage were immunopositive. These results show a progression of immunoexpression of both bcl-2 and p53 from the early histological stages to the late tumor stage, implying that these proteins are upregulated late in the evolution of KS.     

Differential roles for the p101 and p84 regulatory subunits of PI3Kγ in tumor growth and metastasis

Phosphoinositide 3-kinase γ (PI3Kγ) consists of a catalytic subunit p110γ, which forms mutually exclusive dimers with one of the regulatory subunits called p101 and p84/p87(PIKAP). Recently, PI3Kγ emerged as being a potential oncogene because overexpression of the catalytic subunit p110γ or the regulatory subunit p101 leads to oncogenic cellular transformation and malignancy. However, the contribution of the individual subunits to tumor growth and metastasis and the mechanisms involved are not understood. We therefore individually knocked down the PI3Kγ subunits (p84, p101 and p110γ) in MDA-MB-231 cells, which reduced in vitro migration of the cell lines. Knockdown of p110γ or p101 inhibited apoptosis, Akt phosphorylation and lung colonization in SCID mice. Similarly, the knockdown of p110γ and p101 in murine epithelial carcinoma 4T1.2 cells inhibited primary tumor growth and spontaneous metastasis, as well as lung colonization. In contrast, knockdown of p84 in MDA-MB-231 cells enhanced Akt phosphorylation and lung colonization. These findings are the first to implicate differential functions of the two PI3Kγ regulatory subunits in the process of oncogenesis, and indicate that loss of p101 is sufficient to reduce in vivo tumor growth and metastasis to the same extent as that of p110γ.     

Cellular senescence in naevi and immortalisation in melanoma: a role for p16?

Cellular senescence, the irreversible proliferative arrest seen in somatic cells after a limited number of divisions, is considered a crucial barrier to cancer, but direct evidence for this in vivo was lacking until recently. The best-known form of human cell senescence is attributed to telomere shortening and a DNA-damage response through p53 and p21. There is also a more rapid form of senescence, dependent on the p16-retinoblastoma pathway. p16 (CDKN2A) is a known melanoma susceptibility gene. Here, we use retrovirally mediated gene transfer to confirm that the normal form of senescence in cultured human melanocytes involves p16, since disruption of the p16/retinoblastoma pathway is required as well as telomerase activation for immortalisation. Expression (immunostaining) patterns of senescence mediators and markers in melanocytic lesions provide strong evidence that cell senescence occurs in benign melanocytic naevi (moles) in vivo and does not involve p53 or p21 upregulation, although p16 is widely expressed. In comparison, dysplastic naevi and early (radial growth-phase, RGP) melanomas show less p16 and some p53 and p21 immunostaining. All RGP melanomas expressed p21, suggesting areas of p53-mediated senescence, while most areas of advanced (vertical growth-phase) melanomas lacked both p16 and p21, implying escape from both forms of senescence (immortalisation). Moreover, nuclear p16 but not p21 expression can be induced in human melanocytes by oncogenic BRAF, as found in around 80% of naevi. We conclude that cell senescence can form a barrier to melanoma development. This also provides a potential explanation of why p16 is a melanoma suppressor gene.     

p53 gene mutations and p21 protein expression induced independently of p53, by TGF-β and γ-rays in squamous cell carcinoma cells

p53 gene mutation and the influence of TGF-β and γ-rays on p21 promoter activity, p21 mRNA and protein expression were investigated in nine cell lines (OSC-1 to -9) established from metastatic squamous cell carcinomas (SCC) of the cervical lymph nodes. The direct DNA sequence analysis of exons 2 to 11 of the p53 gene revealed 16 point mutations in all cell lines, but neither deletions nor additions were observed. TGF-β upregulated p21 promoter activity by approximately 2-fold of the control and concurrently increased p21 mRNA expression, except in OSC-8 and -9. However, γ-rays suppressed p21 promoter activity, although p21 mRNA expression in irradiated cells was increased except for OSC-8 and -9. In parallel with the messenger expression, p21 protein expression was strongly increased by TGF-β, but only weakly increased by γ-rays. These results indicate that point mutation of the p53 gene is frequent in metastatic SCC cells and p21 mRNA and its protein expression is p53-independently induced by both TGF-β and γ-rays, although the mechanism of induction by TGF-β and γ-rays is different.     

p53 mutations and resistance to chemotherapy: a stab in the back for p73?

p53 gene is a member of a multigene family that includes p53, p63 and p73. The association of p73 and p63 with cell transformation has been elusive as no genetic or epigenetic alteration of these genes has been uncovered yet. Recent work has shown clearly that p73 is an essential component of the signaling pathway that lead to apoptosis after DNA damage induced by cytotoxic agents use in cancer therapy. Furthermore, it has been established that a sub-category of mutant p53 is able to interact with p73 and inhibit its apoptotic activity. Such discovery will be important for a better understanding of the signaling pathway that lead to resistance to chemotherapy.     

p85α mediates p53 K370 acetylation by p300 and regulates its promoter-specific transactivity in the cellular UVB response

Inducible acetylation of p53 at lysine residues has a great impact on regulating the transactivation of this protein, which is associated with cell growth arrest and/or apoptosis under various stress conditions. However, the factor(s) for regulating p53 acetylation remains largely unknown. In the current study, we have shown that p85α, the regulatory subunit of phosphatidylinositol-3-kinase, has a critical role in mediating p53 acetylation and promoter-specific transactivation in the ultraviolet B (UVB) response. Depletion of p85α in mouse embryonic fibroblasts significantly impairs UVB-induced apoptosis, as well as p53 transactivation and acetylation at Lys370 (Lys373 of human p53); however, the accumulation, nuclear translocation and phosphorylation of p53 are not affected. Interestingly, p85α binds to p300, promotes the p300-p53 interaction and the subsequent recruitment of the p53/p300 complex to the promoter region of the specific p53 target gene in response to UVB irradiation. Moreover, ablation of p53 acetylation at Lys370 by site-directed mutagenesis dramatically suppresses UVB-induced expression of the specific p53-responsive gene as well as cell apoptosis. Therefore, we conclude that p85α is a novel regulator of p53-mediated response under certain stress conditions, and targeting the p85α-dependent p53 pathway may be promising for cancer therapy.     

Immunohistochemical Analysis of E-Cadherin,p53 and Inhibin-α Expression in Hydatidiform Mole and Hydropic Abortion

The purpose of this study was to investigate the role of E-cadherin, p53, and inhibin-α immunostaining in the differential diagnosis of hydropic abortion (HA), partial hydatidiform mole (PHM), and complete hydatidiform mole (CHM). E-cadherin, p53, and inhibin-α protein expression patterns were investigated immunohistochemically using paraffin -embedded tissue sections from histologically diagnosed cases of HA (n?=?23), PHM (n?=?24), and CHM (n?=?23). Expression patterns of these markers were scored semi-quantitatively according to the staining intensity, percentage of positive cells, and immunoreactivity score. Classification of cases was established on histologic criteria and supported by the molecular genotyping. Immunostaining allowed the identification of specific cell types with E-cadherin, p53, and inhibin-α expression in all cases. E-cadherin expression was detected on the cell surface of villous cytotrophoblasts. We observed a marked decline in the expression of E-cadherin from HAs to PHMs to CHMs. The p53-positive reaction was restricted to the nucleus of villous cytotrophoblasts. Significantly increased p53 expression was observed in CHMs, compared with HAs and PHMs. The expression of inhibin-α was localised in the cytoplasm of villous syncytiotrophoblasts, and the expression of this marker was significantly higher in PHMs and CHMs than HAs. In conclusion, immunohistochemical analysis of E-cadherin, p53, and inhibin-α expression could serve as a useful adjunct to conventional methods in the differential diagnosis of HA, PHM, and CHM.     

p63 and p73: teammates or adversaries?

In this issue of Cancer Cell, Kovacic and colleagues have reexamined the role of STAT1 in murine models of leukemogenesis. Their studies shed new light on the complex interplay between cell-autonomous contributions and host responsiveness to cancer and elucidate a previously unknown role of STAT1 in tumor progression.     

O,p′-DDD (Mitotane) levels in plasma and tissues during chemotherapy and at autopsy

Summary The distribution of o,p-DDD in various body compartments of patients being treated for metastatic adrenocortical carcinoma was studied. A highly significant semilogarithmic relationship was found between plasma and adipose tissue concentrations during therapy and between levels in plasma and adipose tissue and between plasma and brain at autopsy. A linear relationship was found at autopsy between concentrations in adipose tissue and those in various other tissues, such as tumour and brain. The semilogarithmic relationship can be explained by the assumption of two plasma pools for o,p-DDD, one with low affinity and high capacity and one with high affinity and low capacity.Plasma concentrations must be carefully monitored to obtain an impression of the tumour concentration and to detect impending central nervous system intoxication.     

1p36.32 rearrangements and the role of PI-PLC η2 in nervous tumours

Deletions in the distal region of the short arm of chromosome 1 (1p36) are widely diffuse, both in congenital 1p36 Deletion Syndrome and as somatic abnormalities in tumours. Rearrangements in 1p36 have been described in a broad spectrum of human neoplasias in addition to other chromosomal abnormalities. In neuroblastomas, wide hemizygous deletions in 1p36.23–1p36.32 have been described suggesting that the 1p36 region contains a tumour-suppressor gene involved in malignancy. A role for phosphoinositide (PI)-specific phospholipase C (PLC) η2, whose gene maps on 1p36.32, was suggested. PI-PLC η2 belongs to a family of enzymes related to the phosphoinositide signalling pathway, which provide an important intracellular signalling system involved in a variety of cell functions such as hormone secretion, neurotransmitter signal transduction, cell growth, membrane trafficking, ion channel activity, regulation of the cytoskeleton, cell cycle control and apoptosis. Expression of PI-PLC η2 occurs after birth and continues throughout the life. Synapse formation occurs during a short period of postnatal development. Thus, it is likely that PI-PLC η2 acts in formation and maintenance of the neuronal network in the brain. The fact that PI-PLC η2, a highly neuron-specific isozyme, is abundantly expressed in the postnatal brain suggests the importance of PI-PLC η2 in formation and maintenance of the neuronal network in the postnatal brain. Further studies are required to verify the possible involvement of PI-PLC η2 mutation/deletion in central nervous tumour tissues presenting abnormalities of the 1p36 chromosomal band.