Project description:Melanoma tumors are highly heterogeneous, comprising of many cell populations that vary in their potential for growth and invasion. Differential transcription factor expression contributes to these phenotypic traits. BRN2, a member of the POU domain family of transcription factors is thought to play important roles in melanoma invasion and metastasis. However, how BRN2 functions during the metastatic process of melanoma remains largely unknown. We therefore investigated the effects of BRN2 expression in melanoma cells with no or low constitutive expression using a doxycycline-inducible system. Induction of BRN2 expression led to reduced proliferation and partial resistance to an inhibitor of mutated BRAF. Whole genome profiling analysis revealed novel targets and signaling pathway changes related to prevention of cell death induced by detachment from the extracellular matrix, known as anoikis resistance. Further investigation confirmed increased survival of BRN2 expressing cell lines in non-adherent conditions. Functionally, expression of BRN2 promoted induction of c-MET levels as well as increased phosphorylation of STAT3. Treatment with crizotinib, a c-MET inhibitor, decreased cellular viability of BRN2 expressing cells under non-adherent conditions to death by anoikis. These results highlight the importance of a largely overlooked transcription factor in the progression and metastasis of melanoma, and may suggest a strategy to target BRN2 expressing cells resistant to therapy and cell death by anoikis.
Project description:Melanoma tumors are highly heterogeneous, comprising of many cell populations that vary in their potential for growth and invasion. Differential transcription factor expression contributes to these phenotypic traits. BRN2, a member of the POU domain family of transcription factors is thought to play important roles in melanoma invasion and metastasis. However, the function of BRN2 during the metastatic process of melanoma remains largely unknown. We therefore investigated the effect of BRN2 expression in melanoma cells with no or low constitutive expression using a doxycycline-inducible system. Induction of BRN2 expression led to reduced proliferation and partial resistance to an inhibitor of mutated BRAF. Whole-genome profiling analysis revealed novel targets and signaling pathway changes related to prevention of cell death induced by detachment from the extracellular matrix, known as anoikis resistance. Further investigation confirmed increased survival of BRN2-expressing cell lines in non-adherent conditions. Functionally, expression of BRN2 promoted induction of c-MET levels as well as increased phosphorylation of STAT3. Treatment with crizotinib, a c-MET inhibitor, decreased cellular viability of BRN2-expressing cells under non-adherent conditions to death by anoikis. Alternative inhibitors of c-MET showed similar results. These results highlight the importance of a largely overlooked transcription factor in the progression and metastasis of melanoma, and may suggest a strategy to target BRN2-expressing cells resistant to therapy and cell death by anoikis.
Project description:Melanoma tumors are highly heterogeneous, comprising of different cell types that vary in their potential for growth and invasion. Heterogeneous expression of the Microphthalmia-associated Transcription Factor (MITF) and the POU domain transcription factor BRN2 (POU3F2) has been found in malignant melanoma. Changing expression of these transcription factors as the disease progresses has been linked to the metastatic mechanism of phenotype switching. We therefore investigated the effects of MITF and BRN2 expression in melanoma growth and metastasis. Depletion of MITF resulted in a cell population that had a slowed cell cycle progression, was less invasive in vitro and had hindered tumor and metastasis forming ability in mouse xenograft studies. BRN2 depletion left a cell population with intact proliferation and invasion in vitro; however metastatic growth was significantly reduced in the mouse xenograft model. These results suggest that the proliferative population within melanoma tumors express MITF, and both MITF and BRN2 are important for metastatic growth in vivo. This finding highlights the importance of BRN2 and MITF expression in development of melanoma metastasis.
Project description:Anoikis resistance or evasion of cell death triggered by cell detachment is a hallmark of cancer that is concurrent with cell survival and metastasis. Phenotypes of anoikis resistant cancer cells have been extensively investigated, however, how exposure to suspension stress may lead to acquisition of a anoikis resistance phenotype has not been previously described in detail. Here we show using a spectrum of ovarian cancer cells, that cycles of suspension stress followed by attached growth, leads to adaptation and acquisition of resistance to cell death in suspension . Comparing the stepwise transcriptomic changes as cells acquire resistance, we find strong transcriptional reprogramming in the population with a majority of differentially expressed genes being downregulated during progressive acquisition of anoikis resistance. Adapted anoikis resistant cells display an enhanced dependency on oxidative phosphorylation and are capable of evasion from T cell-mediated immune surveillance. We find that such acquired anoikis resistance is not genetic. However, transcriptional reprogramming is essential to this process as acquisition of such adaptive anoikis resistance invitro and invivo are both exquisitely sensitive to specific inhibition of transcriptional reprogramming. Our data demonstrate that recovery from the verge of anoikis leads to adaptation that promotes metastasis in ovarian cancer, but can be therapeutically prevented by specific inhibitors to transcriptional reprogramming.
Project description:To investigate potential molecular targets that regulate metastasis and metabolism in anoikis-resistance of prostate cancer cells, we have establised anoikis-resistant prostate PC-3 cells with ultra-low attachment 6-well plates (Corning) and employed whole genome microarray expression profiling as a discovery platform to identify differentially expressed genes between anoikis-resistant PC-3 cells and corresponding parental cells.
Project description:Anoikis (detachment-induced cell death) is a specific type of programmed cell death which occurs in response to the loss of the correct extracellular matrix connections. Anoikis resistance is an important mechanism in cancer invasiveness and metastatic behavior. Autophagy, on the other hand, involves the degradation of damaged organelles and the recycling of misfolded proteins and intracellular components. However, the intersection of these two cellular responses in lung cancer cells has not been extensively studied. Here, we identified that upon matrix deprivation, the lymphocyte lineage-specific Ets transcription factor SPIB was activated and directly enhanced SNAP47 transcription in certain lung cancer cells. Loss of attachment-induced autophagy significantly increased anoikis resistance by SPIB activation. Consistent with this function, SPIB depletion by short hairpin RNA abrogated SNAP47 transcriptional activation upon matrix deprivation. Therefore, these data delineate an important role of SPIB in autophagy-mediated anoikis resistance in lung cancer cells. Accordingly, these findings suggest that manipulating SPIB-regulated pathways in vivo and evaluating the impact of anoikis resistance warrant further investigation.
Project description:Anoikis (detachment-induced cell death) is a specific type of programmed cell death which occurs in response to the loss of the correct extracellular matrix connections. Anoikis resistance is an important mechanism in cancer invasiveness and metastatic behavior. Autophagy, on the other hand, involves the degradation of damaged organelles and the recycling of misfolded proteins and intracellular components. However, the intersection of these two cellular responses in lung cancer cells has not been extensively studied. Here, we identified that upon matrix deprivation, the lymphocyte lineage-specific Ets transcription factor SPIB was activated and directly enhanced SNAP47 transcription in certain lung cancer cells. Loss of attachment-induced autophagy significantly increased anoikis resistance by SPIB activation. Consistent with this function, SPIB depletion by short hairpin RNA abrogated SNAP47 transcriptional activation upon matrix deprivation. Therefore, these data delineate an important role of SPIB in autophagy-mediated anoikis resistance in lung cancer cells. Accordingly, these findings suggest that manipulating SPIB-regulated pathways in vivo and evaluating the impact of anoikis resistance warrant further investigation.
Project description:Oxidative stress has been shown to limit metastasis of numerous cancer types including melanoma. A specialized group of 25 proteins containing the 21st amino acid, selenocysteine, plays a central role in oxidative stress resistance, which is a key driver of metastasis. A single selenocysteine tRNA methylation, Um34, is required for the translation of several stress-related selenoproteins in a selenium-dependent manner. Herein, we characterize FTSJ1 as the Um34 methyltransferase and show that its activity is required for the Sec tRNA (tRNASec) Um34 modification. Loss of Um34 affects translation of a subset of selenoproteins and increases melanoma cell sensitivity to oxidative stress while increased Um34 levels promote oxidative stress resistance. Loss of FTSJ1 does not affect primary melanoma tumor growth but abolishes metastatic spread in vivo. Overexpression of FTSJ1 specifically increases melanoma metastasis in vivo. Our work establishes FTSJ1 as the Um34 methyltransfearse and tRNASec Um34 modification as a central regulator of oxidative stress resistance during melanoma metastasis.