Ectopic expression of miR-34a in human metastatic melanoma cells: effects on signaling pathways related to survival, proliferation and cell death

Author(s)

Julia Laura Fernandes Abrantes

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2013-03-15

Examining board members

Carmen Veríssima Ferreira; Carmen Silvia Passos Lima; Silvya Stuchi Maria Engler; Ana Carolina Santos de Souza; Enilza Maria Espreafico

• Advisor: Carmen Veríssima Ferreira

Abstract

Melanoma is the most aggressive form of skin cancer. Its treatment remains a big challenge, since in advanced stage it is extremely refractory to conventional treatments. miR-34a has emerged as an important tumor suppressor, and its expression is normally reduced in cancer cells. To provide more information about the role of miR-34a as a melanoma suppressor, the main goal of this study was to identify key molecular players modulated by ectopic expression of this microRNA in the metastatic melanoma cell line SK-mel-103. miR-34a caused a reduction of melanoma cells viability, what may be related, at least in part, with the increased expression of pro-apoptotic marker, Bax, activation of caspase 3 and PARP-1 cleavage, which indicates that miR-34a triggered apoptosis in melanoma cells. In addition, the expression of CDK4, CDK6, E2F3 and pRb, proteins related to the cell cycle progression, was reduced. An increase in p21 expression, a CDK inhibitor, was also detected in these cells. Some key molecules involved with proliferation and apoptosis processes, such as oncogenic proteins (Axl, AKT, ERK 1/2 kinases, ?- catenin and c-myc) and tumor suppressor proteins (p53 and PTEN), were down- and upregulated by miR-34a, respectively. Interestingly, the autophagic flux was stimulated by miR-34a, but this effect was not correlated with further alterations in cell viability. The increased autophagy occurred probably as a cellular response against the reticulum stress and the protein aggregation induced by miR-34a in melanoma cells, which can also be contributing to the cell death by apoptosis in this context. Our findings brought up novel molecular aspects about the role of miR-34a as melanoma suppressor. The broad action of this microRNA on key molecular players of melanoma aggressiveness was crucial for reprogramming these cells in favor of apoptosis. Altogether, this study pointed out miR-34a as a potential therapeutic agent against advanced melanoma (AU)

• FAPESP's process: 09/15374-8 - Modulation of aggressiveness and escape of melanoma cells
• Grantee: Julia Laura Fernandes Abrantes
• Support Opportunities: Scholarships in Brazil - Doctorate