Overexpression of delta Np63 in a human nasopharyngeal carcinoma cell line downregulates CKIs and enhances cell proliferation

ΔNp63 overexpression promotes oral cancer cell migration through hyperactivated Activin A signaling

Oral cancer is a common malignant tumor of the oral cavity that affects many countries with a prevalent distribution in the Indian subcontinent, with poor prognosis rate on account of locoregional metastases. Gain-of-function mutations in p53 and overexpression of its related transcription factor, p63 are both widely reported events in oral cancers. However, targeting these alterations remains a far-achieved aim due to lack of knowledge on their downstream signaling pathways. In the present study, we characterize the isoforms of p63 and using knockdown strategy, decipher the functions and oncogenic signaling of p63 in oral cancers. Using Microarray and Chromatin Immunoprecipitation experiments, we decipher a novel transcriptional regulatory axis between p63 and Activin A and establish its functional significance in migration of oral cancer cells. Using an orally bioavailable inhibitor of the Activin A pathway to attenuate oral cancer cell migration and invasion, we further demonstrate the targetability of this signaling axis. Our study highlights the oncogenic role of ΔNp63 - Activin A - SMAD2/3 signaling and provides a basis for targeting this oncogenic pathway in oral cancers.

Transcription Factor ATF3 Participates in DeltaNp63-Mediated Proliferation of Corneal Epithelial Cells

Understanding the regulatory mechanisms underlying corneal epithelial cell (CEC) proliferation in vitro may provide the means to boost CEC production in cell therapy for ocular disorders. The transcription factor ΔNp63 plays a crucial role in the proliferation of CECs, but the underlying mechanisms is yet to be elucidated. TP63 and ΔNp63 are encoded by the TP63 gene via alternative promoters. We previously reported that both ΔNp63 and activating transcription factor (ATF3) are substantially expressed in cultured CECs, but the regulatory relationship between ΔNp63 and ATF3 is unknown. In the present study, we found that ΔNp63 increased ATF3 expression and ATF3 promoter activity in cultured CECs. The deletion of the p63 binding core site reduced ATF3 promoter activity. CECs overexpressing ATF3 exhibited significantly greater proliferation than control CECs. ATF3 knockdown suppressed the ΔNp63-induced increase in cell proliferation. Overexpression of ATF3 in CECs significantly elevated protein and mRNA levels of cyclin D. The protein levels of keratin 3/14, integrin β1, and involucrin did not differ between ATF3-overexpressing CECs, ATF3-downregulated CECs, and control cells. In conclusion, our results suggest that ΔNp63 increases CEC proliferation via the ΔNp63/ATF3/CDK pathway.

Whole-Exome Sequencing Study of Familial Nasopharyngeal Carcinoma and Its Implication for Identifying High-Risk Individuals

BACKGROUND

Nasopharyngeal carcinoma (NPC) is closely associated with genetic factors and Epstein-Barr virus infection, showing strong familial aggregation. Individuals with a family history suffer elevated NPC risk, requiring effective genetic counseling for risk stratification and individualized prevention.

METHODS

We performed whole-exome sequencing on 502 familial NPC patients and 404 unaffected relatives and controls. We systematically evaluated the established cancer predisposition genes and investigated novel NPC susceptibility genes, making comparisons with 21 other familial cancers in the UK biobank (N = 5218).

RESULTS

Rare pathogenic mutations in the established cancer predisposition genes were observed in familial NPC patients, including ERCC2 (1.39%), TP63 (1.00%), MUTYH (0.80%), and BRCA1 (0.80%). Additionally, 6 novel susceptibility genes were identified. RAD54L, involved in the DNA repair pathway together with ERCC2, MUTYH, and BRCA1, showed the highest frequency (4.18%) in familial NPC. Enrichment analysis found mutations in TP63 were enriched in familial NPC, and RAD54L and EML2 were enriched in both NPC and other Epstein-Barr virus-associated cancers. Besides rare variants, common variants reported in the studies of sporadic NPC were also associated with familial NPC risk. Individuals in the top quantile of common variant-derived genetic risk score while carrying rare variants exhibited increased NPC risk (odds ratio = 13.47, 95% confidence interval = 6.33 to 28.68, P = 1.48 × 10-11); men in this risk group showed a cumulative lifetime risk of 24.19%, much higher than those in the bottom common variant-derived genetic risk score quantile and without rare variants (2.04%).

CONCLUSIONS

This study expands the catalog of NPC susceptibility genes and provides the potential for risk stratification of individuals with an NPC family history.

ΔNp63α is a super enhancer-enriched master factor controlling the basal-to-luminal differentiation transcriptional program and gene regulatory networks in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) originates via malignant transformation of the pseudostratified nasopharyngeal epithelium, composed of basal and luminal cells. Super enhancers (SEs) are large clusters of cis-elements involved in the regulation of gene expression through epigenetic regulatory mechanisms. In this study, we demonstrated that basal cell-specific proteins are highly expressed, whereas luminal cell proteins are downregulated in NPC, implying a perturbation of basal-to-luminal differentiation during NPC development. We characterized NPC cell models according to different molecular signatures associated with their differentiation status and found that distinct SE landscapes are tightly associated with basal or luminal-like molecular signatures in NPC cells. Furthermore, the transcription of ΔNP63α, a prominent isoform of TP63, was found to be driven by SEs in NPC cells. Data from chromatin immunoprecipitation (ChIP)-sequencing showed that ΔNP63α largely occupied regions of SEs associated with basal cell-specific genes. Silencing of ΔNP63α led to a loss of H3K27ac occupancy at basal-type SEs and triggered a basal-to-luminal gene expression signature switch, suggesting that ΔNP63α is a master factor contributing to the perturbation of luminal differentiation. Integrative transcriptomics analysis also revealed that ΔNP63α acts as a core factor involved in the dysregulation of gene expression in NPC. Furthermore, ΔNP63α enhanced EGF-stimulated NF-κB activation in NPC cells by activating SE-mediated EGFR transcription. Finally, depletion of ΔNP63α in NPC cells induced robust growth inhibition of NPC cells in vitro and in vivo. Our data revealed that ΔNP63α-dependent SE reprogramming contributes to the blockade of luminal differentiation and uncontrolled proliferation in NPC.

Supercharging BRD4 with NUT in carcinoma

NUT carcinoma (NC) is an extremely aggressive squamous cancer with no effective therapy. NC is driven, most commonly, by the BRD4-NUT fusion oncoprotein. BRD4-NUT combines the chromatin-binding bromo- and extraterminal domain-containing (BET) protein, BRD4, with an unstructured, poorly understood protein, NUT, which recruits and activates the histone acetyltransferase p300. Recruitment of p300 to chromatin by BRD4 is believed to lead to the formation of hyperacetylated nuclear foci, as seen by immunofluorescence. BRD4-NUT nuclear foci correspond with massive contiguous regions of chromatin co-enriched with BRD4-NUT, p300, and acetylated histones, termed "megadomains" (MD). Megadomains stretch for as long as 2 MB. Proteomics has defined a BRD4-NUT chromatin complex in which members that associate with BRD4 also exist as rare NUT-fusion partners. This suggests that the common pathogenic denominator is the presence of both BRD4 and NUT, and that the function of BRD4-NUT may mimic that of wild-type BRD4. If so, then MDs may function as massive super-enhancers, activating transcription in a BET-dependent manner. Common targets of MDs across multiple NCs and tissues are three stem cell-related transcription factors frequently implicated in cancer: MYC, SOX2, and TP63. Recently, MDs were found to form a novel nuclear sub-compartment, called subcompartment M (subM), where MD-MD interactions occur both intra- and inter-chromosomally. Included in subM are MYC, SOX2, and TP63. Here we explore the possibility that if MDs are simply large super-enhancers, subM may exist in other cell systems, with broad implications for how 3D organization of the genome may function in gene regulation and maintenance of cell identity. Finally, we discuss how our knowledge of BRD4-NUT function has been leveraged for the therapeutic development of first-in-class BET inhibitors and other targeted strategies.

TP63 links chromatin remodeling and enhancer reprogramming to epidermal differentiation and squamous cell carcinoma development

Squamous cell carcinoma (SCC) is an aggressive malignancy that can originate from various organs. TP63 is a master regulator that plays an essential role in epidermal differentiation. It is also a lineage-dependent oncogene in SCC. ΔNp63α is the prominent isoform of TP63 expressed in epidermal cells and SCC, and overexpression promotes SCC development through a variety of mechanisms. Recently, ΔNp63α was highlighted to act as an epidermal-specific pioneer factor that binds closed chromatin and enhances chromatin accessibility at epidermal enhancers. ΔNp63α coordinates chromatin-remodeling enzymes to orchestrate the tissue-specific enhancer landscape and three-dimensional high-order architecture of chromatin. Moreover, ΔNp63α establishes squamous-like enhancer landscapes to drive oncogenic target expression during SCC development. Importantly, ΔNp63α acts as an upstream regulator of super enhancers to activate a number of oncogenic transcripts linked to poor prognosis in SCC. Mechanistically, ΔNp63α activates genes transcription through physically interacting with a number of epigenetic modulators to establish enhancers and enhance chromatin accessibility. In contrast, ΔNp63α also represses gene transcription via interacting with repressive epigenetic regulators. ΔNp63α expression is regulated at multiple levels, including transcriptional, post-transcriptional, and post-translational levels. In this review, we summarize recent advances of p63 in epigenomic and transcriptional control, as well as the mechanistic regulation of p63.

Ironing out the role of the cyclin-dependent kinase inhibitor, p21 in cancer: Novel iron chelating agents to target p21 expression and activity

Iron (Fe) has become an important target for the development of anti-cancer therapeutics with a number of Fe chelators entering human clinical trials for advanced and resistant cancer. An important aspect of the activity of these compounds is their multiple molecular targets, including those that play roles in arresting the cell cycle, such as the cyclin-dependent kinase inhibitor, p21. At present, the exact mechanism by which Fe chelators regulate p21 expression remains unclear. However, recent studies indicate the ability of chelators to up-regulate p21 at the mRNA level was dependent on the chelator and cell-type investigated. Analysis of the p21 promoter identified that the Sp1-3-binding site played a significant role in the activation of p21 transcription by Fe chelators. Furthermore, there was increased Sp1/ER-α and Sp1/c-Jun complex formation in melanoma cells, suggesting these complexes were involved in p21 promoter activation. Elucidating the mechanisms involved in the regulation of p21 expression in response to Fe chelator treatment in neoplastic cells will further clarify how these agents achieve their anti-tumor activity. It will also enhance our understanding of the complex roles p21 may play in neoplastic cells and lead to the development of more effective and specific anti-cancer therapies.

ΔNp63 promotes abnormal epidermal proliferation in arsenical skin cancers

Arsenic is known to perturb epidermal homeostasis and induce abnormal keratinocyte proliferation, leading to skin carcinogenesis. P63 and its isoforms are essential to regulate epidermal homeostasis. This study aimed to investigate the role of p63 isoforms in abnormal epidermal proliferation induced by arsenic. Using arsenic-induced Bowen's disease (As-BD; an intraepidermal carcinoma) as a disease model, we found that in As-BD, the expression of proliferating basal keratinocytes marker cytokeratin 14 (CK14) and N-terminal truncated p63 isoform (ΔNp63; proliferation regulator) was increased, however, that of the differentiation marker cytokeratin 10 (CK10) and full-length p63 isoform (TAp63; differentiation regulator) was decreased in squamous cells as compared with healthy subjects. These observations were recapitulated in the arsenic-treated skin equivalents (SEs). The SEs showed that arsenic increased epidermal thickness, induced abnormal proliferation, and increased ΔNp63 expression in squamous cells as compared with the control. Treatment of cultured normal human epidermal keratinocytes (HKCs) with arsenic increased CK14 and △Np63 expressions, but decreased TAp63 and CK10 expressions. Furthermore, knockdown of ΔNp63 by RNA interference abrogated arsenic-induced CK14 expression and recovered the reduction of TAp63 and CK10 caused by arsenic. These findings indicated that ΔNp63 is a pivotal regulator in the abnormal cell proliferation in arsenical cancers.

Vimentin regulates differentiation switch via modulation of keratin 14 levels and their expression together correlates with poor prognosis in oral cancer patients

Vimentin is an intermediate filament protein, predominantly expressed in cells of mesenchymal origin, although its aberrant expression is seen in many carcinomas during epithelial mesenchymal transition. In cancer, vimentin expression is associated with the transition from a more differentiated epithelial phenotype to a dedifferentiated state. In view of the perceived role of keratins (Ks) as regulators of differentiation in epithelia, it was important to understand whether vimentin modulates differentiation through the reprogramming of keratins, in transformed cells. To address this, vimentin was stably downregulated in oral cancer derived cells. Further, global keratin profiling was performed after high salt keratin extraction. K5/K14 pair was found to be significantly downregulated, both at protein and mRNA levels upon vimentin downregulation. The previous study from our laboratory has shown a role of the K5/K14 pair in proliferation and differentiation of squamous epithelial cells. Vimentin depleted cells showed an increase in the differentiation state, marked by an increase in the levels of differentiation specific markers K1, involucrin, filaggrin and loricrin while its proliferation status remained unchanged. Rescue experiments with the K5/K14 pair overexpressed in vimentin knockdown background resulted in decreased differentiation state. ΔNp63 emerged as one of the indirect targets of vimentin, through which it modulates the expression levels of K5/K14. Further, immunohistochemistry showed a significant correlation between high vimentin-K14 expression and recurrence/poor survival in oral cancer patients. Thus, in conclusion, vimentin regulates the differentiation switch via modulation of K5/K14 expression. Moreover, vimentin-K14 together may prove to be the novel markers for the prognostication of human oral cancer.

Differential targeting of the cyclin-dependent kinase inhibitor, p21CIP1/WAF1, by chelators with anti-proliferative activity in a range of tumor cell-types

Chelators such as 2-hydroxy-1-napthylaldehyde isonicotinoyl hydrazone (311) and di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) target tumor cell iron pools and inhibit proliferation. These agents also modulate multiple targets, one of which is the cyclin-dependent kinase inhibitor, p21. Hence, this investigation examined the mechanism of action of these compounds in targeting p21. All the chelators up-regulated p21 mRNA in the five tumor cell-types assessed. In contrast, examining their effect on total p21 protein levels, these agents induced either: (1) down-regulation in MCF-7 cells; (2) up-regulation in SK-MEL-28 and CFPAC-1 cells; or (3) had no effect in LNCaP and SK-N-MC cells. The nuclear localization of p21 was also differentially affected by the ligands depending upon the cell-type, with it being decreased in MCF-7 cells, but increased in SK-MEL-28 and CFPAC-1 cells. Further studies assessing the mechanisms responsible for these effects demonstrated that p21 expression was not correlated with p53 status, suggesting a p53-independent mechanism. Considering this, we examined proteins that modulate p21 independently of p53, namely NDRG1, MDM2 and ΔNp63. These studies demonstrated that a dominant negative MDM2 isoform (p75(MDM2)) closely resembled p21 expression in response to chelation in three cell lines. These data suggest MDM2 may be involved in the regulation of p21 by chelators.

Wilms' tumor gene 1 regulates p63 and promotes cell proliferation in squamous cell carcinoma of the head and neck

Background

Wilms’ tumor gene 1 (WT1) can act as a suppressor or activator of tumourigenesis in different types of human malignancies. The role of WT1 in squamous cell carcinoma of the head and neck (SCCHN) is not clear. Overexpression of WT1 has been reported in SCCHN, suggesting a possible oncogenic role for WT1. In the present study we aimed at investigating the function of WT1 and its previously identified protein partners p63 and p53 in the SCCHN cell line FaDu.

Methods

Silencing RNA (siRNA) technology was applied to knockdown of WT1, p63 and p53 in FaDu cells. Cell proliferation was detected using MTT assay. Chromatin immunoprecipitation (ChIP)/PCR analysis was performed to confirm the effect of WT1 on the p63 promoter. Protein co-immunoprecipitation (co-IP) was used to find protein interaction between WT1 and p53/p63. Microarray analysis was used to identify changes of gene expression in response to knockdown of either WT1 or p63. WT1 RNA level was detected using real-time quantitative PCR (RT-qPCR) in patients with SCCHN.

Results

We found that WT1 and p63 promoted cell proliferation, while mutant p53 (R248L) possessed the ability to suppress cell proliferation. We reported a novel positive correlation between WT1 and p63 expression. Subsequently, p63 was identified as a WT1 target gene. Furthermore, expression of 18 genes involved in cell proliferation, cell cycle regulation and DNA replication was significantly altered by downregulation of WT1 and p63 expression. Several known WT1 and p63 target genes were affected by WT1 knockdown. Protein interaction was demonstrated between WT1 and p53 but not between WT1 and p63. Additionally, high WT1 mRNA levels were detected in SCCHN patient samples.

Conclusions

Our findings suggest that WT1 and p63 act as oncogenes in SCCHN, affecting multiple genes involved in cancer cell growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1356-0) contains supplementary material, which is available to authorized users.

Nasopharyngeal Carcinoma: An Evolving Role for the Epstein-Barr Virus

The Epstein-Barr herpesvirus (EBV) is an important human pathogen that is closely linked to several major malignancies including the major epithelial tumor, undifferentiated nasopharyngeal carcinoma (NPC). This important tumor occurs with elevated incidence in specific areas, particularly in southern China but also in Mediterranean Africa and some regions of the Middle East. Regardless of tumor prevalence, undifferentiated NPC is consistently associated with EBV. The consistent detection of EBV in all cases of NPC, the maintenance of the viral genome in every cell, and the continued expression of viral gene products suggest that EBV is a necessary factor for the malignant growth in vivo. However, the molecular characterization of the infection and identification of critical events have been hampered by the difficulty in developing in vitro models of NPC. Epithelial cell infection is difficult in vitro and in contrast to B-cell infection does not result in immortalization and transformation. Cell lines established from NPC usually do not retain the genome, and the successful establishment of tumor xenografts is difficult. However, critical genetic changes that contribute to the onset and progression of NPC and key molecular properties of the viral genes expressed in NPC have been identified. In some cases, viral expression becomes increasingly restricted during tumor progression and tumor cells may express only the viral nuclear antigen EBNA1 and viral noncoding RNAs. As NPC develops in the immunocompetent, the continued progression of deregulated growth likely reflects the combination of expression of viral oncogenes in some cells and viral noncoding RNAs that likely function synergistically with changes in cellular RNA and miRNA expression.

MicroRNA-301b promotes cell invasiveness through targeting TP63 in pancreatic carcinoma cells

Recent studies have demonstrated that deregulated microRNA (miR) expression is implicated in the development of human cancers. In the aberrant miR expression, miR-301 is upregulated in cancers, such as pancreatic, colorectal and oral carcinoma. Based on this evidence, we investigated the contribution of miR-301 to pancreatic carcinoma and the novel target genes of miR-301 in pancreatic carcinoma. In this study, we analyzed the effects of enforced and inhibited expression of miR-301b expression in the Panc-1 and BxPC-3 cell lines. MiR-301b expression levels were associated with cell invasiveness in both cell lines. Additional experiments indicated that miR-301b influences invasiveness through CDH1. Moreover microRNA target search algorithms and experimental strategies suggested that miR-301b suppressed TP63 expression as a novel target of miR-301b. Remarkably, miR-301b was also found to be associated with NF-κB activity in both cell lines. In summary, overexpressed miR-301b may suppress TP63 expression and contributes to promote cell invasiveness and to enhance gemcitabine resistance in pancreatic carcinoma cells. Thus, miR-301b may have potential as a novel therapeutic target for cancer treatment due to its stimulatory effects on cell invasiveness.

Possible involvement of ΔNp63 downregulation in the invasion and metastasis of oral squamous cell carcinoma via induction of a mesenchymal phenotype

Epithelial-to-mesenchymal transition (EMT), an essential developmental program, is involved in tumor progression. ΔNp63, a homolog of p53, is associated with the EMT program, but the detailed mechanism remains to be elucidated. In this study, we investigated the role of ΔNp63 in EMT during progression of oral squamous cell carcinoma (OSCC). Five OSCC cell lines and specimens from 78 patients with OSCC were used. The expressions of ΔNp63, p63α, p63β and epithelial markers (cytokeratins 5 and 14) was detected in the OSCC cells, but not in SQUU-B cells (high metastatic potential). E-cadherin was expressed in all OSCC cells. Mesenchymal markers were strongly expressed in the SQUU-B cells. Knockdown of endogenous ΔNp63 in HSC-2 cells induced morphological changes to the spindle shape, decreased the expression of epithelial markers, increased the expression of mesenchymal markers, increased migration and reduced proliferation. By contrast, SQUU-B cells overexpressing ΔNp63β showed changed their morphology from stromal cell-like to epithelial cells. However, E-cadherin expression was not affected by ΔNp63 knockdown or overexpression. Immunohistochemical staining revealed that cancer cells expressing vimentin were found at the invasive front in the OSCC specimens. The intensity of ΔNp63 expression was also decreased in these cells. Interestingly, the vimentin positivity or decreased intensity of ΔNp63 was positively associated with metastases and poor prognosis in the OSCC patients. These results indicated that ΔNp63 downregulation in cancer cells induces a mesenchymal phenotype that is related to tumor progression of OSCC.

EVI1 targets ΔNp63 and upregulates the cyclin dependent kinase inhibitor p21 independent of p53 to delay cell cycle progression and cell proliferation in colon cancer cells

Several lines of evidence suggest that specific transcriptional events are involved in cell cycle, proliferation and differentiation processes; however, their deregulation by proto-oncogenes are involved in the development of leukemia and tumors. One such proto-oncogene is ecotropic viral integration site I which can differentially effect cell cycle progression and proliferation, in cell types of different origin. Our data for the first time shows that ecotropic viral integration site I binds to ΔNp63 promoter element directly and down regulates its expression. Down regulation of ΔNp63 induces the expression of p21 in HT-29 cells and also in colon carcinoma cells that do not express p53 including patient samples expressing low level of p53, that eventually delay cell cycle progression at G0/G1 phase. Concomitant silencing of ecotropic viral integration site I from the cells or introduction of ΔNp63 to the cells significantly rescued this phenotype, indicating the growth defect induced by ΔNp63 deficiency to be, at least in part, attributable to ecotropic viral integration site I function. The mutual regulation between ecotropic viral integration site I and ΔNp63 may constitute a novel axis which might affect the downstream pathways in cells that do not express functional p53.

Expression profiling of 21 biomolecules in locally advanced nasopharyngeal carcinomas of Caucasian patients

Background

Since scarce data exist on the pathogenesis of nasopharyngeal carcinoma in Caucasian patients, we attempted to elucidate the responsible molecular pathways in this patient population.

Methods

Formalin-fixed paraffin-embedded tumor tissue samples from 107 patients, diagnosed with locally-advanced nasopharyngeal carcinoma and treated with chemotherapy or chemo-radiotherapy, were analyzed by immunohistochemistry for the expression of the following proteins: E-cadherin, P-cadherin, Fascin-1, Cyclin D1, COX-2, EGFR, VEGF-A, VEGF-C, VEGFR-2, VEGFR-3, ERCC1, p53, p63, Ki67, MAPT, phospho-p44/42MAPK, PTEN, phospho-AKT, phospho-mTOR, and phospho-GSK-3β. EBER status was assessed by in situ hybridization. The majority of the cases were included in tissue microarray. All stains were performed and assessed centrally by two pathologists. The median follow-up time was 76.8 (42.3 – 99.2) months.

Results

Biomolecules expressed in >90% of cases were: p53, COX-2, P-cadherin, EBER, phospho-GSK-3β, and Fascin-1. WHO II+III tumors were more frequently EBER & PTEN positive and VEGF-A negative. Advanced age was significantly associated with positive phospho-GSK-3β and ERCC1 expression; male gender with positive phospho-AKT and phospho-p44/42MAPK; and worse performance status (1 or 2) with negative Ki67, ERCC1, PTEN, and phospho-mTOR expression. Earlier disease stage was closely associated with p63, MAPT, PTEN, and Cyclin D1 positivity. Univariate Cox regression analysis highlighted Cyclin D1 as a negative prognostic factor for disease-free survival (p=0.034) and EBER as a positive one for overall survival (p=0.048). In multivariate analysis, advanced age and stage, poor performance status, and positive ERCC1 emerged as predictors of worse disease-free and overall survival, as opposed to positive phospho-mTOR. Clustering analysis defined two protein-expression groups being predictive of better overall survival (p=0.043).

Conclusions

Our study is the first to examine the activation and interaction of established biomolecules and signaling pathways in Caucasian NPC patients in an effort to reveal new therapeutic targets.

Loss of p63 and its microRNA-205 target results in enhanced cell migration and metastasis in prostate cancer

p63 inhibits metastasis. Here, we show that p63 (both TAp63 and ΔNp63 isoforms) regulates expression of miR-205 in prostate cancer (PCa) cells, and miR-205 is essential for the inhibitory effects of p63 on markers of epithelial-mesenchymal transition (EMT), such as ZEB1 and vimentin. Correspondingly, the inhibitory effect of p63 on EMT markers and cell migration is reverted by anti-miR-205. p53 mutants inhibit expression of both p63 and miR-205, and the cell migration, in a cell line expressing endogenous mutated p53, can be abrogated by pre-miR-205 or silencing of mutated p53. In accordance with this in vitro data, ΔNp63 or miR-205 significantly inhibits the incidence of lung metastasis in vivo in a mouse tail vein model. Similarly, one or both components of the p63/miR-205 axis were absent in metastases or colonized lymph nodes in a set of 218 human prostate cancer samples. This was confirmed in an independent clinical data set of 281 patients. Loss of this axis was associated with higher Gleason scores, an increased likelihood of metastatic and infiltration events, and worse prognosis. These data suggest that p63/miR-205 may be a useful clinical predictor of metastatic behavior in prostate cancer.

Genome-wide analysis reveals recurrent structural abnormalities of TP63 and other p53-related genes in peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) are aggressive malignancies of mature T lymphocytes with 5-year overall survival rates of only ∼ 35%. Improvement in outcomes has been stymied by poor understanding of the genetics and molecular pathogenesis of PTCL, with a resulting paucity of molecular targets for therapy. We developed bioinformatic tools to identify chromosomal rearrangements using genome-wide, next-generation sequencing analysis of mate-pair DNA libraries and applied these tools to 16 PTCL patient tissue samples and 6 PTCL cell lines. Thirteen recurrent abnormalities were identified, of which 5 involved p53-related genes (TP53, TP63, CDKN2A, WWOX, and ANKRD11). Among these abnormalities were novel TP63 rearrangements encoding fusion proteins homologous to ΔNp63, a dominant-negative p63 isoform that inhibits the p53 pathway. TP63 rearrangements were seen in 11 (5.8%) of 190 PTCLs and were associated with inferior overall survival; they also were detected in 2 (1.2%) of 164 diffuse large B-cell lymphomas. As TP53 mutations are rare in PTCL compared with other malignancies, our findings suggest that a constellation of alternate genetic abnormalities may contribute to disruption of p53-associated tumor suppressor function in PTCL.

Downregulation of p57kip² promotes cell invasion via LIMK/cofilin pathway in human nasopharyngeal carcinoma cells

The members of Rho family are well known for their regulation of actin cytoskeleton to control cell migration. The Cip/kip members of cyclin-dependent (CDK) inhibitors have shown to implicate in cell migration and cytoskeletal dynamics. p57(kip2) , a CDK inhibitor, is frequently down-regulated in several malignancy tumors. However, its biological roles in human nasopharyngeal carcinoma (NPC) cells remained to be investigated. Here, we found p57(kip2) has nuclear and cytoplasm distributions and depletion of endogenous p57(kip2) did not change the cell-cycle progression. Inhibition of cell proliferation by mitomycin C promoted FBS-mediated cell migration and accompanied with the downregulation of ΔNp63α and p57(kip2), but did not change the level of p27(kip1) , another CDK inhibitor. By using siRNA transfection and cell migration/invasion assays, we found that knockdown of p57(kip2) , but not ΔNp63α, involved in promotion of NPC cell migration and invasion via decrease of phospho-cofilin (p-cofilin). Treatment with Y-27632, a specific ROCK inhibitor, we found that dysregulation of ROCK/cofilin pathway decreased p-cofilin expression and induced cell migration. This change of p-cofilin induced actin remodeling and pronounced increase of membrane protrusions. Further, silence of p57(kip2) not only decreased the interaction between p57(kip2) and LIMK-1 assayed by immunoprecipitation but also reduced the level of phospho-LIMK1/2. Therefore, this study indicated that dysregulation of p57(kip2) promoted cell migration and invasion through modulation of LIMK/cofilin signaling and suggested this induction of inappropriate cell motility might contribute to promoting tumor cell for metastasis.

p63 is a suppressor of tumorigenesis and metastasis interacting with mutant p53

p53 mutations, occurring in two-thirds of all human cancers, confer a gain of function phenotype, including the ability to form metastasis, the determining feature in the prognosis of most human cancer. This effect seems mediated at least partially by its ability to physically interact with p63, thus affecting a cell invasion pathway, and accordingly, p63 is deregulated in human cancers. In addition, p63, as an 'epithelial organizer', directly impinges on epidermal mesenchimal transition, stemness, senescence, cell death and cell cycle arrest, all determinant in cancer, and thus p63 affects chemosensitivity and chemoresistance. This demonstrates an important role for p63 in cancer development and its progression, and the aim of this review is to set this new evidence that links p63 to metastasis within the context of the long conserved other functions of p63.

ΔNp63α regulates keratinocyte proliferation by controlling PTEN expression and localization

ΔNp63α, implicated as an oncogene, is upregulated by activated Akt, part of a well-known cell survival pathway. Inhibition of Akt activation by phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and the presence of putative p63-binding sites in the pten promoter led us to investigate whether ΔNp63α regulates PTEN expression. Knockdown of ΔNp63α led to increases in PTEN levels and loss of activated Akt, while overexpression of ΔNp63α decreased PTEN levels and elevated active Akt. The repression of PTEN by ΔNp63α occurs independently of p53 status, as loss of ΔNp63α increases PTEN expression in cell lines with and without functional p53. In addition, decreased levels of ΔNp63α resulted in an increase in nuclear PTEN. Conversely, in vivo nuclear PTEN was absent in the proliferative basal layer of the epidermis where ΔNp63α expression is highest. Additionally, we show that in keratinocytes a balance between ΔNp63α and PTEN regulates Akt activation and maintains normal proliferation rates. This balance is disrupted in non-melanoma skin cancers through increased ΔNp63α levels, and could enhance proliferation and subsequent neoplastic development. Our studies show that ΔNp63α negatively regulates PTEN, thereby providing a feedback loop between PTEN, Akt and ΔNp63α, which has an integral role in skin cancer development.

Role of p63 in cancer development

Since their initial identification p53 homologues p63 and p73 have been expected to play a role in cancer development due to their close homology to p53, notoriously one of the most mutated genes in cancer. However soon after their discovery the awareness that these genes were rarely mutated in cancer seemed to indicate that they did not play a role in its development. However a large number of data collected in the following years indicated that altered expression rather than mutation could be found in different neoplasia and play a role in its biology. In particular p63 due to its fundamental role in epithelial development seems to play a role in a number of tumors of epithelial origin. In this review we summarize some of the evidence linking p63 to carcinogenesis.

Resveratrol-induced p53-independent apoptosis of human nasopharyngeal carcinoma cells is correlated with the downregulation of ΔNp63

ΔNp63, the N-terminal truncated isoform of p63, has been found to be overexpressed in several human epithelial cancers, including nasopharyngeal carcinomas (NPCs), suggesting a function in carcinogenesis. Trans-resveratrol (RSV) has been shown to exert proapoptotic activities through a p53-dependent or p53-independent pathway in various cancer cells. However, the effects of RSV on NPC are still unexplored. In this study, we investigated the apoptotic effects of RSV on ΔNp63-overexpressing NPC cell lines. We showed that RSV (12-100 μ) induced dose-dependent growth suppression, cell-cycle arrest in the S phase and caspase-dependent apoptosis in NPC-TW076 and NPC-TW039 cells. The RSV effect was accompanied by the downregulation of ΔNp63 and the upregulation of p53 protein in a dose-dependent manner. By using small-interfering RNA (siRNA) technology, we found that the targeted silencing of ΔNp63 induced apoptosis and sensitized the NPC cells to RSV-induced apoptosis through caspase-3 activation, whereas suppression of p53 by siRNA did not inhibit RSV-induced apoptosis. Furthermore, transfection with p53 siRNA or pretreatment with caspase inhibitors (Z-VAD-fmk or Z-DEVD-fmk) had no influence on the RSV downregulation of ΔNp63. Interestingly, ecoptic expression of ΔNp63 did not significantly block RSV-induced cell death and was also downregulated after RSV treatment. Downregulation of ΔNp63 by RSV was shown to occur at the mRNA transcript and post-translational levels. Importantly, RSV enhanced chemotheraptic drug-induced apoptosis in NPC and two human carcinoma cell lines, HT1376 and Hep3B cells. These results suggested that ΔNp63, but not p53, is a molecular target of RSV-induced apoptosis and the regulation of ΔNp63 expression by RSV may provide a therapeutic effect of RSV in human NPC.

DeltaNp63 overexpression, alone and in combination with other biomarkers, predicts the development of oral cancer in patients with leukoplakia

PURPOSE

The risk of malignant transformation of oral preneoplastic lesion (OPL) is difficult to assess. DeltaNp63 is an early oncoprotein associated with mucosal tumorigenesis. The purpose of this study was to assess DeltaNp63 expression in OPL and its role as a marker of oral cancer risk.

EXPERIMENTAL DESIGN

DeltaNp63 expression was determined using immunohistochemistry in 152 OPL patients included in a clinical trial comparing retinyl palmitate alone or plus beta-carotene with low-dose 13-cis-retinoic acid. The associations between DeltaNp63 expression as well as DeltaNp63 expression with other potential risk factors for oral cancer development were analyzed.

RESULTS

DeltaNp63 expression was positive in 41 (27%) patients, clusters of intraepithelial inflammatory cells (EIC) were noted in 37 (26%) patients, and podoplanin (previously reported) was positive in 56 (37%) patients. Significantly more patients whose lesions were DeltaNp63 positive or exhibited EIC developed oral cancers. In the multicovariate analysis including age, treatment, and histologic status as cofactors, positive DeltaNp63 expression was associated with an increased hazard ratio of 3.308 (95% confidence interval, 1.663-6.580; P = 0.0007). Patients whose lesions showed positive DeltaNp63, podoplanin, and EIC had the highest oral cancer risk with a hazard ratio of 4.372 (95% confidence interval, 1.912-9.992; P = 0.0005) and 61% oral cancer development rate at 5 years compared with 15% of other OPL patients (P < 0.0001).

CONCLUSION

DeltaNp63 overepression in OPL is associated with increased oral cancer risk. Together, DeltaNp63, podoplanin, and EIC may be used as biomarkers to identify OPL patients with substantially high oral cancer risk.