MicroRNAs (miRNAs) are a class of small non coding RNAs of 18–25 nucleotides in length. The temporal or short-lived expression of the miRNAs modulates gene expression post transcriptionally. Studies have revealed that miRNAs deregulation correlates and is involved with the initiation and progression of human tumors. Cervical cancer (CC) displays notably increased or decreased expression of a large number of cellular oncogenic or tumor suppressive miRNAs, respectively. However, understanding the potential role of miRNAs in CC is still limited. In CC, the high-risk human papillomaviruses (HR-HPVs) infection can affect the miRNAs expression through oncoprotein E6 and E7 that contribute to viral pathogenesis, although other viral proteins might also be involved. This deregulation in the miRNAs expression has an important role in the hallmarks of CC. Interestingly, the miRNA expression profile in CC can discriminate between normal and tumor tissue and the extraordinary stability of miRNAs makes it suitable to serve as diagnostic and prognostic biomarkers of cancer. In this review, we will summarize the role of the HR-HPVs in miRNA expression, the role of miRNAs in the hallmarks of CC, and the use of miRNAs as potential prognostic biomarkers in CC.

The contribution of the Wnt signaling pathway to human papilloma virus (HPV)-induced carcinogenesis is poorly understood. In high-grade dysplastic lesions that are caused by high-risk HPVs (HR-HPV), β-catenin is often located in the cell nucleus, which suggests that Wnt pathway may be involved in the development of HPV-related carcinomas. Most of the oncogenic potential of HR-HPVs resides on the PDZ-binding domain of E6 protein. We hypothesized that the PDZ-binding domain of the HPV16-E6 oncoprotein induces the nuclear accumulation of β-catenin due to its capacity to degrade PDZ-containing cellular targets. To test this hypothesis, we evaluated the staining pattern of β-catenin in the skin epidermis of transgenic mice expressing the full-length E6 oncoprotein (K14E6 mice) and measured LacZ gene expression in K14E6 mice that were crossed with a strain expressing LacZ that was knocked into the Axin2 locus (Axin2^+/LacZ mice). Here, we show that the E6 oncoprotein enhances the nuclear accumulation of β-catenin, the accumulation of cellular β-catenin–responsive genes, and the expression of LacZ. None of these effects were observed when a truncated E6 oncoprotein that lacks the PDZ-binding domain was expressed alone (K14E6ΔPDZ mice) or in combination with Axin2^+/LacZ. Conversely, cotransfection with either E6 or E6ΔPDZ similarly enhanced canonical Wnt signaling in short-term in vitro assays that used a luciferase Wnt/β-catenin/TCF-dependent promoter. We propose that the activation of canonical Wnt signaling could be induced by the HPV16-E6 oncoprotein; however, the participation of the E6 PDZ-binding domain seems to be important in in vivo models only. Mol Cancer Res; 10(2); 250–8. ©2011 AACR.

To gain insights into the antitumor mechanisms of resveratrol (RES), we carried out a DNA microarray analysis in the breast cancer cell line MCF-7 to study the global gene expression profile induced by RES treatment. The mRNA expression level of 19 734 well-characterized human genes from MCF-7 cells was determined using Affymetrix microarrays under two different RES treatments: 150 μmol/l (IC₅₀) and 250 μmol/l during 48 h. A total of 1211 genes were found to have altered mRNA expression levels of two-fold or more in the 150 μmol/l RES-treated group (518 upregulated and 693 downregulated genes). However, 2412 genes were found to have altered expression levels of two-fold or more in the 250 μmol/l RES-treated group (651 genes upregulated and 1761 downregulated). Under both conditions of RES treatment, several genes of mismatch repair, DNA replication, homologous recombination (HR), and cell cycle were strongly inhibited. Consistently, we found decreased protein levels of the MRN complex (MRE11-NBS1-RAD50), an important complex of the HR DNA repair pathway. The ability to inhibit the expression of DNA repair genes by RES could help to overcome drug resistance commonly shown by transformed cells and to provide a solid basis for carrying out clinical trials with RES, alone or in combination with other agents, to enhance treatment efficacy, reduce toxicity, and overcome chemoresistance. Remarkably, after RES treatment, we found a decrease in NBS1 and MRE11 protein levels, two major proteins involved in HR, which suggests that RES could be used to sensitize cancer cells to cell death in combination with anticancer drugs.

Resveratrol (RES), a polyphenol compound with anti‑proliferative properties, has been previously evaluated for its beneficial effects against a variety of tumour cells. The current study elucidated the means by which RES enhances the anti‑proliferative effects of cisplatin (CIS) on MCF‑7 cells, focusing on the inhibitory effects on DNA repair of double‑strand breaks (DSBs). Chemoresistant MCF‑7 cells (MCF‑7R) were generated by continuous exposure to low concentrations of CIS (10 µM CIS‑IC40) during 5 passages, with the IC50 value increasing ~3‑fold. Using an MTT assay, we estimated the changes in IC50 for CIS in MCF‑7, T47‑D, MDA‑MB‑231 and MCF‑7R cells in the presence of RES. The relative transcript level of Nbs‑1, Mre‑11 and Rad‑50 genes was assessed using RT‑qPCR analysis. Rad51 and H2AX [pSer139] protein expression was determined by western blot analysis. RES at 50 and 100 µM significantly enhanced the anti‑proliferative effects of CIS in both MCF‑7 and MCF‑7R cells, decreasing the IC50 values for CIS to one‑tenth and one‑sixth, respectively. A total of 100 µM RES decreased the relative transcript levels of homologous recombination (HR) initiation complex components and the Rad51 protein level in MCF‑7 and MCF‑7R cells. After 48 h of CIS DNA damage, the levels of Rad51 protein increased, but this effect was inhibited by 100 µM RES. RES also maintained serine 139 phosphorylation of histone H2AX, suggesting that RES prevents the repair of DSBs. It was observed that RES exerts an antagonistic effect over CIS on the activation of Rad51 and sustained phosphorylation of H2AX. The results suggest that RES in combination with DNA damage‑based therapy has potential as a strategy to overcome resistance and provide much safer and more effective treatment for breast cancer.

HER2 over-expression is related with a poor prognosis in patients with invasive breast cancer tumors. Clinical associations have reported that somatic mutations of p53 more frequently detected in cases of sporadic breast cancer of the HER2 subtypes, besides a high percentage of HER2-amplifying tumors carry germline mutations of p53. The mechanisms responsible for the acquisition of oncogenic functions of p53 mutant proteins (mtp53), known as Gain of Function (GOF), over HER2 expression have not been reported. The objective of this study was to evaluate a possible relationship between p53 mutants and HER2 regulation. HER2 expression (transcription and protein), as well as HER2 protein stabilization have been evaluated after inducing or silencing of p53 mutants’ expression in cell lines. Finally, we evaluated the interaction of the p53 mutants over the HER2 receptor promoter. Higher HER2 expression in cell lines harboring endogenous mtp53 compared with wt or null expression of p53 cell lines. Transfection of p53 mutants (R248Q and R273C) in cell lines increased the expression of HER2. Silencing of p53 mutants, decrease HER2 expression. The p53 mutants R248Q and R273C significantly increase the luciferase activity on the HER2 promoter, and both mutants also promote acetylation of H3 and H4 histones binding in it. These findings show for the first time that p53 mutants induce over-expression of HER2 at transcriptional level of the HER2 protein. Our results could have clinical implications in breast cancer and other types of cancer where HER2 is over-expressed and used as a therapy target.

Cervical cancer is the second most frequent tumor type in women worldwide with cases developing clinical recurrence, metastasis, and chemoresistance. The cancer stem cells (CSC) may be implicated in tumor resistance to therapy. RESveratrol (RES), a natural compound, is an antioxidant with multiple beneficial activities. We previously determined that the expression of RAD51 is decreased by RES. The aim of our study was to examine molecular mechanism by which CSC from HeLa cultures exhibit chemoresistance. We hypothesized CSC repair more efficiently DNA breaks and that RAD51 plays an important role in this mechanism. We found that CSC, derived from cervical cancer cell lines, overexpress RAD51 and are less sensitive to Etoposide (VP16). We inhibited RAD51 in CSC-enriched cultures using RES or siRNA against RAD51 messenger RNA and observed a decrease in cell viability and induction of apoptosis when treated simultaneously with VP16. In addition, we found that inhibition of RAD51 expression using RES also sensitizes CSC to VP16 treatment. Our results suggest that resveratrol is effective to sensitize cervical CSC because of RAD51 inhibition, targeting high RAD51 expressing CD49f-positive cells, which supports the possible therapeutic application of RES as a novel agent to treat cancer.