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 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: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:We use optical induction of Brn2 to probe mechanisms for gating embryonic stem cell differentiation mRNA-seq time-course following Brn2 induciton
Project description:Lung cancer is an intrinsically highly metastatic disease and the leading cause of cancer-related deaths worldwide. Although discovery of molecular aberrations in lung adenocarcinomas has led to development of effective targeted therapies, corresponding “drivers” in lung squamous carcinomas (LUSC) have not materialized. Extensive molecular profiling has revealed LUSC tumors have non-recurrent somatic mutations and are largely driven by copy number alterations. Because microRNAs (miRs) play increasingly important roles in regulating metastasis-relevant pathways, we evaluated whether miRs can regulate LUSC progression. By integrating bioinformatics of the Cancer Genome Atlas (TCGA) with novel, highly metastatic LUSC models, we found that miR-671-5p is a key inhibitor of LUSC metastasis. Surprisingly, miR-671-5p regulates LUSC metastasis by inhibiting a circular RNA (circRNA), CDR1as. Although the putative function of CDR1as is through miR-7 sponging, we found miR-671-5p more potently silences an axis of CDR1as and its anti-sense transcript, cerebellar degeneration related antigen 1 (CDR1). To our knowledge, no function of CDR1 has ever been described. We found loss of CDR1as and CDR1 significantly inhibited LUSC metastases. Intriguingly, CDR1 was strongly associated with an epithelial-mesenchymal transition (EMT) program in LUSC tumors, and was sufficient to promote metastases, increased migration and substrate-independent survival, known as anoikis-resistance. CDR1, which directly interacts with AP1 and COPI subunits, no longer promoted migration and anoikis-resistance upon blockade of Golgi trafficking. Our findings reveal a miR/circRNA axis that regulates LUSC metastases through an enigmatic protein, CDR1.
Project description:About half of all melanomas harbor a constitutively active mutant BRAFV600E/K kinase that can be selectively inhibited by targeted BRAF inhibitors (BRAFi). While patients treated with BRAFi initially exhibit measurable clinical improvement, the majority of patients eventually develop drug resistance and relapse. We observe significant elevation of WNT5A in a subset of tumors from patients exhibiting disease progression on BRAFi therapy. WNT5A transcript and protein are also elevated in BRAFi-resistant melanoma cell lines generated by long-term in vitro treatment with BRAFi. RNAi-mediated reduction in levels of endogenous WNT5A in melanoma decreases cell growth, increases apoptosis in response to BRAFi challenge, and decreases the activity of pro-survival AKT signaling. Overexpression of WNT5A conversely promotes melanoma growth and tumorigenesis and activates AKT signaling. Similar to WNT5A knockdown, knockdown of the WNT receptors FZD7 and RYK inhibits growth, sensitizes melanoma cells to BRAFi, and reduces AKT activation. Together, these findings suggest that chronic BRAF inhibition elevates WNT5A expression, which then acts through FZD7 and RYK to promote AKT signaling, leading to increased growth and therapeutic resistance. Increased WNT5A expression in BRAFi-resistant melanomas also correlates with an associated transcriptional signature, which identifies potential therapeutic targets to reduce clinical resistance to BRAFi. Expression of WNT5A-correlated genes was compared in melanoma cell lines generated to be resistant to PLX4032 and the their associated naïve parental line Basal expression of the WNT5A-correlated genes was also measured in experiments comparing each naïve line to a mixed reference pool containing equal amounts of 47 melanoma cell lines.
Project description:How mechanical stress might influence the resistance of cancer cells to cell death is currently unknown. To address this, we mimicked the mechanical constrictions that cancer cells might encounter when invading through rich tumoral stroma or undergoing intra- and extravasation. We found that extreme constrictional migration (ECM) but not compression increases the resistance of breast cancer cells to anoikis, a variant of apoptosis triggered by loss of cell adhesions. We also found that Inhibitory of Apoptosis Proteins (IAPs) are responsible for ECM-triggered resistance to anoikis. Together with enhanced cell motility and resistance to natural killer-mediated immune-surveillance, we show that anoikis resistant ECM mechanically-challenged cancer cells have a marked advantage to form lung metastatic lesions. Taken together, our study connects the constrictional mechanical stress typically characterizing the metastatic colonization with the resistance to cell death, while therapeutically targeting the IAPs by SMAC mimetics could counteract anoikis resistance in breast cancer cells.