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See detailThe microRNA-371~373 cluster represses colon cancer initiation and metastatic colonization by inhibiting the TGFBR2/ID1 signaling axis.
Ullmann, Pit UL; Rodriguez, Fabien UL; Schmitz, Martine UL et al

in Cancer research (2018)

The vast majority of colorectal cancer (CRC)-related deaths can be attributed to metastatic spreading of the disease. Therefore, deciphering molecular mechanisms of metastatic dissemination is a key ... [more ▼]

The vast majority of colorectal cancer (CRC)-related deaths can be attributed to metastatic spreading of the disease. Therefore, deciphering molecular mechanisms of metastatic dissemination is a key prerequisite to improve future treatment options. With this aim, we took advantage of different CRC cell lines and recently established primary cultures enriched in colon cancer stem cells (CSCs) - also known as tumor-initiating cells (TICs) - to identify genes and microRNAs (miRNAs) with regulatory functions in CRC progression. We show here that metastasis-derived TICs display increased capacity for self-renewal, transforming growth factor beta (TGF-beta) signaling activity, and reduced expression of the miR-371~373 cluster compared to non-metastatic cultures. TGF-beta receptor 2 (TGFBR2) and aldehyde dehydrogenase A1 (ALDH1A1) were identified as important target genes of the miR-371~373 cluster. In addition, TGFBR2 repression, either by direct knockdown or indirectly via overexpression of the entire miR-371~373 cluster, decreased tumor-initiating potential of TICs. We observed significantly reduced in vitro self-renewal activity as well as lowered tumor-initiation and metastatic outgrowth capacity in vivo following stable overexpression of the miR-371~373 cluster in different colon TIC cultures. Inhibitor of DNA binding 1 (ID1) was affected by both TGFBR2 and miR-371~373 cluster alterations. Functional sphere and tumor formation as well as metastatic dissemination assays validated the link between miR-371~373 and ID1. Altogether, our results establish the miR-371~373/TGFBR2/ID1 signaling axis as a novel regulatory mechanism of TIC self-renewal and metastatic colonization. [less ▲]

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See detailLoss of Myosin Vb in colorectal cancer is a strong prognostic factor for disease recurrence
Letellier, Elisabeth UL; Schmitz, Martine UL; Ginolhac, Aurélien UL et al

in British Journal of Cancer (2017), 117(11), 1689-1701

Background: Selecting the most beneficial treatment regimens for colorectal cancer (CRC) patients remains challenging due to a lack of prognostic markers. Members of the Myosin family, proteins recognized ... [more ▼]

Background: Selecting the most beneficial treatment regimens for colorectal cancer (CRC) patients remains challenging due to a lack of prognostic markers. Members of the Myosin family, proteins recognized to play a major role in trafficking and polarization of cells, have recently been reported to be closely associated with several types of cancer and might thus serve as potential prognostic markers in the context of CRC. Methods: We used a previously established meta-analysis of publicly available gene expression data to analyse the expression of different members of the Myosin V family, namely MYO5A, 5B, and 5C, in CRC. Using laser-microdissected material as well as tissue microarrays from paired human CRC samples, we validated both RNA and protein expression of MYO5B and its known adapter proteins (RAB8A and RAB25) in an independent patient cohort. Finally, we assessed the prognostic value of both MYO5B and its adapter-coupled combinatorial gene expression signatures. Results: The meta-analysis as well as an independent patient cohort study revealed a methylation-independent loss of MYO5B expression in CRC that matched disease progression. Although MYO5B mutations were identified in a small number of patients, these cannot be solely responsible for the common down-regulation observed in CRC patients. Significantly, CRC patients with low MYO5B expression displayed shorter overall, disease- and metastasis-free survival, a trend that was further reinforced when RAB8A expression was also taken into account. Conclusions: Our data identifies MYO5B as a powerful prognostic biomarker in CRC, especially in early stages (stages I and II), which might help stratifying patients with stage II for adjuvant chemotherapy. [less ▲]

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See detailHypoxia-responsive miR-210 promotes self-renewal capacity of colon tumor-initiating cells by repressing ISCU and by inducing lactate production
Ullmann, Pit UL; qureshi-baig, komal; Rodriguez, Fabien UL et al

in Oncotarget (2016)

Low oxygen concentrations (hypoxia) are known to affect the cellular metabolism and have been suggested to regulate a subpopulation of cancer cells with tumorigenic properties, the so-called tumor ... [more ▼]

Low oxygen concentrations (hypoxia) are known to affect the cellular metabolism and have been suggested to regulate a subpopulation of cancer cells with tumorigenic properties, the so-called tumor-initiating cells (TICs). To better understand the mechanism of hypoxia-induced TIC activation, we set out to study the role of hypoxia-responsive miRNAs in recently established colon cancer patientderived TICs. We were able to show that low oxygen concentrations consistently lead to the upregulation of miR-210 in different primary TIC-enriched cultures. Both stable overexpression of miR-210 and knockdown of its target gene ISCU resulted in enhanced TIC self-renewal. We could validate the tumorigenic properties of miR- 210 in in vivo experiments by showing that ectopic expression of miR-210 results in increased tumor incidence. Furthermore, enhanced miR-210 expression correlated with reduced TCA cycle activity and increased lactate levels. Importantly, by blocking lactate production via inhibition of LDHA, we could reverse the promoting effect of miR-210 on self-renewal capacity, thereby emphasizing the regulatory impact of the glycolytic phenotype on colon TIC properties. Finally, by assessing expression levels in patient tissue, we could demonstrate the clinical relevance of the miR-210/ISCU signaling axis for colorectal carcinoma. Taken together, our study highlights the importance of hypoxia-induced miR-210 in the regulation of colon cancer initiation. [less ▲]

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