No abstract

Deregulation of miRNAs contributes to the development of distinct cancer types, including melanoma, an aggressive form of skin cancer characterized by high metastatic potential and poor prognosis. The expression of a set of 580 miRNAs was investigated in a model of murine melanoma progression, comprising non-metastatic (4C11-) and metastatic melanoma (4C11+) cells. A significant increase in miR-138-5p expression was found in the metastatic 4C11+ melanoma cells compared to 4C11-, which prompted us to investigate its role in melanoma aggressiveness. Functional assays, including anoikis resistance, colony formation, collective migration, serum-deprived growth capacity, as well as in vivo tumor growth and experimental metastasis were performed in 4C11- cells stably overexpressing miR-138-5p. miR-138-5p induced an aggressive phenotype in mouse melanoma cell lines leading to increased proliferation, migration and cell viability under stress conditions. Moreover, by overexpressing miR-138-5p, low-growing and non-metastatic 4C11- cells became highly proliferative and metastatic in vivo , similar to the metastatic 4C11+ cells. Luciferase reporter analysis identified the tumor suppressor Trp53 as a direct target of miR-138-5p. Using data sets from independent melanoma cohorts, miR-138-5p and P53 expression were also found deregulated in human melanoma samples, with their levels negatively and positively correlated with prognosis, respectively. Our data shows that the overexpression of miR-138-5p contributes to melanoma metastasis through the direct suppression of Trp53 .

phiC31-mediated gene therapy resulted in an important improvement in IDUA-/- mice, including locomotion, although the obstacles that need to be overcome to enable long-term gene therapy for MPSI are also noted.

miRNAs are non-coding RNAs that bind to mRNA targets and disturb their stability and/or translation, thus acting in gene posttranscriptional regulation. It is predicted that over 30% of mRNAs are regulated by miRNAs. Therefore these molecules are considered essential in the processing of many biological responses, such as cell proliferation, apoptosis, and stress responsiveness. As miRNAs participate of virtually all cellular pathways, their deregulation is critical to cancer development. Consequently, loss or gain of miRNAs function may contribute to tumor progression. Little is known about the regulation of miRNAs and understanding the events that lead to changes in their expression may provide new perspectives for cancer treatment. Among distinct types of cancer, melanoma has special implications. It is characterized as a complex disease, originated from a malignant transformation of melanocytes. Despite being rare, its metastatic form is usually incurable, which makes melanoma the major death cause of all skin cancers. Some molecular pathways are frequently disrupted in melanoma, and miRNAs probably have a decisive role on these alterations. Therefore, this review aims to discuss new findings about miRNAs in melanoma fields, underlying epigenetic processes, and also to argue possibilities of using miRNAs in melanoma diagnosis and therapy.

Initially described as a potent cyclin-dependent kinase inhibitor and thus a negative regulator of cell cycle, p21waf1/cip1 is a protein whose expression is often altered in cancer. Paradoxically, its upregulation has been correlated with aggressiveness and poor prognosis. p21waf1/cip1 fits the definition of antagonistic duality, since its cytoplasmic functions differ from its nuclear tasks. Our group had previously developed a murine melanoma progression model, which culminated in the establishment of cell lines representing different stages in melanoma genesis. Surprisingly, we detected overexpression of p21waf1/cip1 protein in a metastatic melanoma cell line (4C11+), which exhibits highly aggressive behavior. Despite its aberrant overexpression has already been described in melanoma, including metastases, little is known about the impact of its ectopic overexpression in melanoma aggressiveness. We performed viral-mediated overexpression and downregulation of p21waf1/cip1 in the non-metastatic melanoma lineage (4C11-) which does not express this protein and in the metastatic melanoma cell line (4C11+), respectively, and assessed for its impact on melanoma survival upon Dacarbazine treatment. Flow cytometry analyses were conducted to investigate p21waf1/cip1 cell cycle control in these lineages. Through Western blot analysis, we also evaluated the expression of phospho-Akt and phospho-p21 as well as p21waf1/cip1 subcellular localization, in an attempt to investigate the mechanisms underlying ectopic location of p21waf1/cip1 and thus its oncogenic activities. Our research shows that upregulated cytoplasmic p21waf1/cip1 increases metastatic melanoma survival upon Dacarbazine treatment, which can be reverted by p21waf1/cip1 silencing. We also detected high levels of phospho-Akt(Ser473) and phospho-p21(Thr145), which are determinant in promoting p21waf1/cip1 cytoplasmic retention. Using Wortmannin, a PI3K inhibitor that prevents Akt activation, cytoplasmic p21waf1/cip1 level was substantially diminished. Importantly, we identified high levels of p21waf1/cip1 and phospho-p21waf1/cip1 in patients-derived metastatic melanoma cells. We provided new insights about molecular pathways involved in Dacarbazine-associated resistance in melanomas, pointing p21waf1/cip1 and PI3K/Akt as key contributors in this process. Altogether, our findings contribute to not only design new therapeutic approaches against metastatic melanoma, but also help to elucidate the contradictory and complex role exerted by p21waf1/cip1 in cancer. Supported by FAPESP and CNPq Citation Format: Gabriela Nana Colaneri, Adriana Taveira Cruz, Débora CP Silva, Roberta Sessa Stilhano, Sang Won Han, Miriam G. Jasiulionis. Cytoplasmic p21WAF1/CIP1 increases metastatic melanoma survival upon chemotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1167.