ABSTRACT
Aims: Retinoblastoma is a childhood ocular tumor rapidly developing from the immature cells of the retina due to loss of functional retinoblastoma protein. Digoxin, a cardiac glycoside, has been reported to be effective in inducing apoptosis, cell cycle arrest, and cytotoxic effects on human cancers. In this regard, the present study aims to investigate whether digoxin could suppress retinoblastoma cancer through the regulation of transforming growth factor-β (TGF-β) signaling pathway. Methodology: The effects of digoxin on Y-79 cells, retinoblastoma cancer cell line, were investigated using MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazoli-umbromide) and BrdU (bromodeoxyuridine) assays to measure cellular cytotoxicity effects and cell apoptosis, respectively. Also, a qPCR assay was employed to analyze the mRNA expression levels of TGFβ signaling pathway including C-MYC, P21, P15, TGFβRI, TGFβRII, and SMAD2, 3, and 4 genes. Results: The results of the cell function assays revealed that digoxin inhibited the cell viability and proliferation of Y-79 cells. In addition, it was found that digoxin significantly suppressed C-MYC expression and enhanced the expression of P21, P15, SMAD2 and SMAD4 genes in a dose-and time-dependent manner. However, the obtained results could not detect any significant effect of digoxin on TGFβRI, TGFβRII and SMAD3 genes. Conclusion: Taken together, the findings of the present study suggest that digoxin could be a potential therapeutic agent in the treatment of retinoblastoma by regulating the cell cycle genes via a non-canonical TGF-β signaling pathway.
ABSTRACT
Aims: The homeoprotein TGIFLX (transforming growth factor-β-induced factor 2-like, Xlinked), which is essential in male reproduction and development and likely oncogenic when aberrantly expressed in prostate. We have previously shown an aberrant expression of TGIFLX in the majority of human prostate tumors. However, mechanism by which TGIFLX acts in prostate cancer is unknown. The aim of this study was to investigate the effects of overexpression of wild-type TGIFLX (wt-TGIFLX) on LNCaP, human prostate adenocarcinoma cells. Study Design: As a prospective study, we used adenovirus expression system for evaluation of TGIFLX expression effects on mammalian cells. Place and Duration of Study: Medical Genetics Department, Tehran University of Medical Sciences (TUMS), between December 2009 and July 2012. Methodology: We cloned entire coding sequence of TGIFLX gene into adenovirus and subsequently LNCaP cells were transfected with the recombinant virus harboring TGIFLX cDNA or control. The TGIFLX expression was confirmed by microscopic analysis and RT-PCR technique. Following molecular cloning and characterization of TGIFLX transcription factor, we then studied the effects of overexpression of TGIFLX in LNCaP cells on mRNA expression of BAX and BCL2 genes. Results: Our results showed that overexpression of TGIFLX downregulated BCL2 gene (P<0.05) and upregulated BAX gene (P<0.05) at transcript level. Our results suggested that TGIFLX could be a tumor suppressor gene and might be involved in initiation and/or development. Conclusion: TGIFLX can play a role as a transcriptional modulator of the genes involved in cell cycle pathway. But still more investigations are necessitated for clarifying this claim.