The dysregulation of gene expression is an enabling hallmark of cancer. Computational analysis of transcriptomics data from human cancer specimens, complemented with exhaustive clinical annotation, provides an opportunity to identify core regulators of the tumorigenic process. Here we exploit well-annotated clinical datasets of prostate cancer for the discovery of transcriptional regulators relevant to prostate cancer. Following this rationale, we identify Microphthalmia-associated transcription factor (MITF) as a prostate tumor suppressor among a subset of transcription factors. Importantly, we further interrogate transcriptomics and clinical data to refine MITF perturbation-based empirical assays and unveil Crystallin Alpha B (CRYAB) as an unprecedented direct target of the transcription factor that is, at least in part, responsible for its tumor-suppressive activity in prostate cancer. This evidence was supported by the enhanced prognostic potential of a signature based on the concomitant alteration of MITF and CRYAB in prostate cancer patients. In sum, our study provides proof-of-concept evidence of the potential of the bioinformatics screen of publicly available cancer patient databases as discovery platforms, and demonstrates that the MITF-CRYAB axis controls prostate cancer biology.

• MeSH
• alpha-Crystallin B Chain genetics   MeSH
• PC-3 Cells MeSH
• Humans MeSH
• Mice, Nude MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Tumor Suppressor Proteins genetics   MeSH
• Prostatic Neoplasms genetics   pathology   MeSH
• Prognosis MeSH
• Gene Expression Regulation, Neoplastic genetics   MeSH
• Microphthalmia-Associated Transcription Factor genetics   MeSH
• Transcription Factors genetics   MeSH
• Transcriptome genetics   MeSH
• Computational Biology methods   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• alpha-Crystallin B Chain MeSH
• MITF protein, human MeSH Browser
• Tumor Suppressor Proteins MeSH
• Microphthalmia-Associated Transcription Factor MeSH
• Transcription Factors MeSH

The sonic Hedgehog/GLI signaling pathway (HH) is critical for maintaining tissue polarity in development and contributes to tumor stemness. Transcription factors GLI1⁻3 are the downstream effectors of HH and activate oncogenic targets. To explore the completeness of the expression of HH components in tumor cells, we performed a screen for all HH proteins in a wide spectrum of 56 tumor cell lines of various origin using Western blot analysis. Generally, all HH proteins were expressed. Important factors GLI1 and GLI2 were always expressed, only exceptionally one of them was lowered, suggesting the functionality of HH in all tumors tested. We determined the effect of a GLI inhibitor GANT61 on proliferation in 16 chosen cell lines. More than half of tumor cells were sensitive to GANT61 to various extents. GANT61 killed the sensitive cells through apoptosis. The inhibition of reporter activity containing 12xGLI consensus sites by GANT61 and cyclopamine roughly correlated with cell proliferation influenced by GANT61. Our results recognize the sensitivity of tumor cell types to GANT61 in cell culture and support a critical role for GLI factors in tumor progression through restraining apoptosis. The use of GANT61 in combined targeted therapy of sensitive tumors, such as melanomas, seems to be immensely helpful.

• Keywords
• GANT61, GLI, Hedgehog, apoptosis, tumor cell lines,
• MeSH
• HeLa Cells MeSH
• Nuclear Proteins metabolism   MeSH
• Jurkat Cells MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Neoplasms drug therapy   metabolism   MeSH
• Disease Progression MeSH
• Cell Proliferation drug effects   MeSH
• Zinc Finger Protein GLI1 metabolism   MeSH
• Zinc Finger Protein Gli2 metabolism   MeSH
• Hedgehog Proteins metabolism   MeSH
• Pyridines pharmacology   MeSH
• Pyrimidines pharmacology   MeSH
• Gene Expression Regulation, Neoplastic drug effects   MeSH
• Signal Transduction drug effects   MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• GANT 61 MeSH Browser
• GLI1 protein, human MeSH Browser
• GLI2 protein, human MeSH Browser
• Nuclear Proteins MeSH
• Zinc Finger Protein GLI1 MeSH
• Zinc Finger Protein Gli2 MeSH
• Hedgehog Proteins MeSH
• Pyridines MeSH
• Pyrimidines MeSH

Melanoma arises from neural crest-derived melanocytes which reside mostly in the skin in an adult organism. Epithelial-mesenchymal transition (EMT) is a tumorigenic programme through which cells acquire mesenchymal, more pro-oncogenic phenotype. The reversible phenotype switching is an event still not completely understood in melanoma. The EMT features and increased invasiveness are associated with lower levels of the pivotal lineage identity maintaining and melanoma-specific transcription factor MITF (microphthalmia-associated transcription factor), whereas increased proliferation is linked to higher MITF levels. However, the precise role of MITF in phenotype switching is still loosely characterized. To exclude the changes occurring upstream of MITF during MITF regulation in vivo, we employed a model whereby MITF expression was inducibly regulated by shRNA in melanoma cell lines. We found that the decrease in MITF caused only moderate attenuation of proliferation of the whole cell line population. Proliferation was decreased in five of 15 isolated clones, in three of them profoundly. Reduction in MITF levels alone did not generally produce EMT-like characteristics. The stem cell marker levels also did not change appreciably, only a sharp increase in SOX2 accompanied MITF down-regulation. Oppositely, the downstream differentiation markers and the MITF transcriptional targets melastatin and tyrosinase were profoundly decreased, as well as the downstream target livin. Surprisingly, after the MITF decline, invasiveness was not appreciably affected, independently of proliferation. The results suggest that low levels of MITF may still maintain relatively high proliferation and might reflect, rather than cause, the EMT-like changes occurring in melanoma.

• Keywords
• MITF, differentiation, invasiveness, melanoma, phenotype switching, proliferation,
• MeSH
• Cell Differentiation * drug effects   MeSH
• Doxorubicin pharmacology   MeSH
• Epithelial-Mesenchymal Transition drug effects   genetics   MeSH
• Phenotype MeSH
• Neoplasm Invasiveness MeSH
• Cell Cycle Checkpoints drug effects   genetics   MeSH
• Humans MeSH
• Melanoma genetics   pathology   MeSH
• RNA, Messenger genetics   metabolism   MeSH
• Biomarkers, Tumor metabolism   MeSH
• Cell Line, Tumor MeSH
• Neoplastic Stem Cells drug effects   metabolism   MeSH
• Cell Movement drug effects   genetics   MeSH
• Cell Proliferation drug effects   MeSH
• Gene Expression Regulation, Neoplastic drug effects   MeSH
• Microphthalmia-Associated Transcription Factor genetics   metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Doxorubicin MeSH
• RNA, Messenger MeSH
• Biomarkers, Tumor MeSH
• Microphthalmia-Associated Transcription Factor MeSH