Investigation of the effect of LET-7C expression on autophagy in breast cancer cell lines

Autophagy is a lysosomal catabolic pathway of degradation of long-lived proteins, damaged organelles and unfolded protein aggregates. It has been known that autophagy plays a role in certain diseases such as cancer, autoinflammatory diseases and neurodegenerative disorders. MicroRNA(miRNA) is defined 19-25 nucleotids in length, single stranded, small non-coding RNA molecules. MiRNA's have a role post-transcriptional regulation of gene expression. MiRNAs are known to take roles in tumor development, metastasis and invasion as tumor suppressor or oncogene. The deregulation of miRNA expression has been observed in breast cancer. Let-7c acts as a tumor suppressor and has been found to be lower in many tumors. In this study, it has been investigated levels of let-7c expression in SKBR-3, MCF-7, CRL-2329 breast cancer cell line and CRL-4010 normal breast epithelial cell line and its effects on autophagy using qRT-PCR, GFP-LC3, western blotting technique in this study. It was found that levels of let-7c expression are markedly lower in MCF-7 and CRL-2329 than normal breast epithelial cell line using qRT-PCR. Over-exspression of let-7c was shown to increase autophagosom in SKBR-3 and CRL-2329 by GFP-LC3 technique. Furthermore, levels of Atg9A were significantly decreased in SKBR-3 and CRL-4010 and the ratio of LC3II/I was higher in CRL-4010. In further studies, the relationship between Let7c and its predicted target ATG9A, and the therapeutic effects of let7c might be better understood in breast cancer.