14 research outputs found
Tbx3 represses E-cadherin expression and enhances melanoma invasiveness.
No full textThe T-box transcription factors Tbx2 and Tbx3 are overexpressed in many cancers and in melanoma promote proliferation by actively suppressing senescence. Whether they also contribute to tumor progression via other mechanisms is not known. Here, we identify a novel role for these factors, providing evidence that Tbx3, and potentially Tbx2, directly repress the expression of E-cadherin, a keratinocyte-melanoma adhesion molecule whose loss is required for the acquisition of an invasive phenotype. Overexpression of Tbx2 and Tbx3 in melanoma cells down-regulates endogenous E-cadherin expression, whereas depletion of Tbx3, but not Tbx2, increases E-cadherin mRNA and protein levels and decreases melanoma invasiveness in vitro. Consistent with these observations, in melanoma tissue, Tbx3 and E-cadherin expression are inversely correlated. Depletion of Tbx3 also leads to substantial up-regulation of Tbx2. The results suggest that Tbx2 and Tbx3 may play a dual role during the radial to vertical growth phase transition by both inhibiting senescence via repression of p21(CIP1) expression, and enhancing melanoma invasiveness by decreasing E-cadherin levels
RALP, A NOVEL PROGNOSTIC MOLECULAR MARKER IN MELANOMA, IS INVOLVED IN THE NOTCH PATHWAY
No full textMelanoma is an aggressive disease with high metastatic potential and resistance to cytotoxic agents. Early-stage melanomas can be successfully cured by surgery and, as in all solid tumours, morbidity and mortality of melanoma are a consequence of local invasion and metastatic spread. The molecular mechanisms involved in the progression of the malignancy, the genetic markers associated to metastatic melanoma dissemination and the acquisition of chemoresistance are only beginning to be defined. An understanding of the molecular biology of melanoma provides a necessary basis to enable the generation of more effective therapeutic modalities.
RaLP, a new member of the SHC family of adaptor proteins was previously characterized in our laboratory as a determinant in the regulation of migration of melanoma cells in short-term assays in vitro. In this study we further characterized the role of RaLP in the progression of melanoma. We have verified that the expression of RaLP significantly correlates with the most important prognostic markers of melanoma (Breslow thickness, Clark’s level of invasion, ulceration, mitotic index and presence of metastasis in lymph nodes) and that patients with RaLP expressing tumours had reduced disease-free survival and overall survival, suggesting that RaLP can be identified as a novel prognostic molecular marker and an independent prediction factor of melanoma progression. We have shown that permanent RaLP silencing does not interfere with the proliferation of three different metastatic melanoma cell lines, while it significantly decreases their migration and this phenomenon was observed even after extended time in culture. The phenotype could be rescued by the overexpression of RaLP in the silenced cells, suggesting that RaLP is a central molecule that positively regulates migration of melanoma cells. Besides regulating migratory abilities of the melanoma cells, RaLP positively influences their invasive potential, by regulating collagen matrix digestion. We also tested cell – cell and cell – ECM adhesion abilities of melanoma cells after RaLP ablation. We observed that RaLP decreases adhesion of the cells to each other in cell – cell adhesion assays and negatively regulates adhesion of melanoma cells to different matrices in cell – ECM adhesion assay. Analyzing gene expression profiles of RaLP – proficient and – deficient cells we have shown that RaLP is involved in the regulation of the NOTCH molecular pathway.
Our in vitro studies suggest that RaLP expression in melanoma might facilitate dissociation of metastatic cells from a tumour mass by loosening cell – cell adhesion, and favour invasion of the surrounding tissues. We still do not know the exact signalling cascade by which RaLP regulates cell motility and adhesion processes and additional studies are necessary to fully understand its role in melanoma progression
Melanoma : targeting signaling pathways and RaLP
No full textBackground: Metastatic melanoma remains one of the most aggressive forms of cancer, with a survival expectation of above six months only in rare cases. Despite advances in the characterization of the underlying molecular pathways and in the development of specific targeted treatments, available chemo- and immuno-therapy are unable to prolong survival significantly in advanced-stage melanoma. Rai like protein (RaLP) is a newly identified Src homology 2 domain containing (Shc) family member selectively expressed during the transition to metastatic melanoma and thus is a potential melanoma-specific drugable target. Objective: To summarize progress in the ongoing therapeutic approaches to metastatic melanoma and discuss RaLP as a potential novel therapeutic target. Methods: Current understanding of the major signaling pathways involved in melanoma metastatization and of the corresponding pharmacological inhibitors is discussed. Conclusion : RaLP might represent a new drugable target for the treatment of metastatic disease
MicroRNA and gene co-expression networks characterize biological and clinical behavior of rhabdomyosarcomas
No full textAbstractRhabdomyosarcomas (RMS) in children and adolescents are heterogeneous sarcomas broadly defined by skeletal muscle features and the presence/absence of PAX3/7-FOXO1 fusion genes. MicroRNAs are small non-coding RNAs that regulate gene expression in a cell context specific manner. Sequencing analyses of microRNAs in 64 RMS revealed expression patterns separating skeletal muscle, fusion gene positive and negative RMS. Integration with parallel gene expression data assigned biological functions to 12 co-expression networks/modules that reassuringly included myogenic roles strongly correlated with microRNAs known in myogenesis and RMS development. Modules also correlated with clinical outcome and fusion status. Regulation of microRNAs by the fusion protein was demonstrated after PAX3-FOXO1 reduction, exemplified by miR-9-5p. MiR-9-5p levels correlated with poor outcome, even within fusion gene positive RMS, and were higher in metastatic versus non-metastatic disease. MiR-9-5p reduction inhibited RMS cell migration. Our findings reveal microRNAs in a regulatory framework of biological and clinical significance in RMS
Role for the histone demethylase KDM4B in rhabdomyosarcoma via CDK6 and CCNA2: compensation by KDM4A and Apoptotic Response of Targeting Both KDM4B and KDM4A
No full textHistone demethylases are epigenetic modulators that play key roles in regulating gene expression related to many critical cellular functions and are emerging as promising therapeutic targets in a number of tumor types. We previously identified histone demethylase family members as overexpressed in the pediatric sarcoma, rhabdomyosarcoma. Here we show high sensitivity of rhabdomyosarcoma cells to a pan-histone demethylase inhibitor, JIB-04 and identify a key role for the histone demethylase KDM4B in rhabdomyosarcoma cell growth through an RNAi-screening approach. Decreasing KDM4B levels affected cell cycle progression and transcription of G1/S and G2/M checkpoint genes including CDK6 and CCNA2, which are bound by KDM4B in their promoter regions. However, after sustained knockdown of KDM4B, rhabdomyosarcoma cell growth recovered. We show that this can be attributed to acquired molecular compensation via recruitment of KDM4A to the promoter regions of CDK6 and CCNA2 that are otherwise bound by KDM4B. Furthermore, upfront silencing of both KDM4B and KDM4A led to RMS cell apoptosis, not seen by reducing either alone. To circumvent compensation and elicit stronger therapeutic responses, our study supports targeting histone demethylase sub-family proteins through selective poly-pharmacology as a therapeutic approach.</p
Shcd binds dock4, promotes ameboid motility and metastasis dissemination, predicting poor prognosis in melanoma
No full textMetastases are the primary cause of cancer-related deaths. The underlying molecular and biological mechanisms remain, however, elusive, thus preventing the design of specific therapies. In melanomas, the metastatic process is influenced by the acquisition of metastasis-associated mutational and epigenetic traits and the activation of metastatic-specific signaling pathways in the primary melanoma. In the current study, we investigated the role of an adaptor protein of the Shc family (ShcD) in the acquisition of metastatic properties by melanoma cells, exploiting our cohort of patient-derived xenografts (PDXs). We provide evidence that the depletion of ShcD expression increases a spread cell shape and the capability of melanoma cells to attach to the extracellular matrix while its overexpression switches their morphology from elongated to rounded on 3D matrices, enhances cells’ invasive phenotype, as observed on collagen gel, and favors metastasis formation in vivo. ShcD overexpression sustains amoeboid movement in melanoma cells, by suppressing the Rac1 signaling pathway through the confinement of DOCK4 in the cytoplasm. Inactivation of the ShcD signaling pathway makes melanoma cells more sensitive to therapeutic treatments. Consistently, ShcD expression predicts poor outcome in a cohort of 183 primary melanoma patients
Pharmacological EZH2 inhibition combined with retinoic acid treatment promotes differentiation and apoptosis in rhabdomyosarcoma cells
No full textBackground: rhabdomyosarcomas (RMS) are predominantly paediatric sarcomas thought to originate from muscle precursor cells due to impaired myogenic differentiation. Despite intensive treatment, 5-year survival for patients with advanced disease remains low (< 30%), highlighting a need for novel therapies to improve outcomes. Differentiation therapeutics are agents that induce differentiation of cancer cells from malignant to benign. The histone methyltransferase, Enhancer of Zeste Homolog 2 (EZH2) suppresses normal skeletal muscle differentiation and is highly expressed in RMS tumours. Results: we demonstrate combining inhibition of the epigenetic modulator EZH2 with the differentiating agent retinoic acid (RA) is more effective at reducing cell proliferation in RMS cell lines than single agents alone. In PAX3-FOXO1 positive RMS cells this is due to an RA-driven induction of the interferon pathway resulting in apoptosis. In fusion negative RMS, combination therapy led to an EZH2i-driven upregulation of myogenic signalling resulting in differentiation. In both subtypes, EZH2 is significantly associated with enrichment of trimethylated lysine 27 on histone 3 (H3K27me3) in genes that are downregulated in untreated RMS cells and upregulated with EZH2 inhibitor treatment. These results provide insight into the mechanism that drives the anti-cancer effect of the EZH2/RA single agent and combination treatment and indicate that the reduction of EZH2 activity combined with the induction of RA signalling represents a potential novel therapeutic strategy to treat both subtypes of RMS. Conclusions: the results of this study demonstrate the potential utility of combining EZH2 inhibitors with differentiation agents for the treatment of paediatric rhabdomyosarcomas. As EZH2 inhibitors are currently undergoing clinical trials for adult and paediatric solid tumours and retinoic acid differentiation agents are already in clinical use this presents a readily translatable potential therapeutic strategy. Moreover, as inhibition of EZH2 in the poor prognosis FPRMS subtype results in an inflammatory response, it is conceivable that this strategy may also synergise with immunotherapies for a more effective treatment in these patients.</p
Catalytic inhibition of KDM1A in Ewing sarcoma is insufficient as a therapeutic strategy.
No full textBACKGROUND: Ewing sarcoma and desmoplastic small round cell tumors (DSRCT) are rare and clinically aggressive sarcomas usually characterized by oncogenic fusion proteins involving EWS. Emerging studies of Ewing sarcoma have demonstrated EWS-FLI1-driven chromatin remodeling as a key aspect of tumorigenicity. In particular, the lysine-specific demethylase KDM1A/LSD1 is linked to transcriptional regulation of target genes orchestrated by the EWS portion of the fusion protein interacting with repressive chromatin-remodeling complexes. Consistent with this model, depletion of KDM1A supports it is a molecular therapeutic target in Ewing sarcoma cells, but effective drugs need to be identified. PROCEDURE: A comprehensive phenotypic analysis of the effects of catalytic KDM1A inhibitors ORY-1001 and GSK2879552, including clinically relevant doses, was carried out in 2D and 3D spheroid models of Ewing sarcoma and DSRCT. RESULTS: Catalytic inhibition of KDM1A did not affect cell viability in 2D and 3D assays and had no impact on invasion in a 3D assay. CONCLUSIONS: Overall, evidence presented here does not support inhibition of KDM1A catalytic demethylase activity as an effective therapeutic strategy for Ewing sarcoma or DSRCT. However, roles of KDM1A beyond its demethylase activity should be considered for these sarcomas
FGF7–FGFR2 autocrine signaling increases growth and chemoresistance of fusion‐positive rhabdomyosarcomas
No full textRhabdomyosarcomas are aggressive pediatric soft-tissue sarcomas and include high-risk PAX3-FOXO1 fusion-gene-positive cases. Fibroblast growth factor receptor 4 (FGFR4) is known to contribute to rhabdomyosarcoma progression; here, we sought to investigate the involvement and potential for therapeutic targeting of other FGFRs in this disease. Cell-based screening of FGFR inhibitors with potential for clinical repurposing (NVP-BGJ398, nintedanib, dovitinib and ponatinib) revealed greater sensitivity of fusion-gene-positive versus -negative rhabdomyosarcoma cell lines and was shown to be correlated with high expression of FGFR2 and its specific ligand, FGF7. Furthermore, patient samples exhibit higher mRNA levels of FGFR2 and FGF7 in fusion-gene-positive versus -negative rhabdomyosarcomas. Sustained intracellular mitogen-activated protein kinase (MAPK) activity and FGF7 secretion into culture media during serum starvation of PAX3-FOXO1 rhabdomyosarcoma cells together with decreased cell viability after genetic silencing of FGFR2 or FGF7 was in keeping with a novel FGF7-FGFR2 autocrine loop. FGFR inhibition with NVP-BGJ398 reduced viability and was synergistic with SN-38, the active metabolite of irinotecan. In vivo, NVP-BGJ398 abrogated xenograft growth and warrants further investigation in combination with irinotecan as a therapeutic strategy for fusion-gene-positive rhabdomyosarcomas
