Project description:We analyzed, by HTA 2.0, the GBM cell lines LN-18, LN-229, and U-87 MG after fluoresence-activated cell sorting (FACS) into ABCB5+ and ABCB5- fractions. Poor prognosis associated with glioblastoma multiforme (GBM) results from tumor resistance to therapy and high rate of recurrence. Compelling evidence suggests this is driven by subpopulations of slow-proliferating cancer stem cells with tumor-initiating potential. ATP-binding cassette member B5 (ABCB5) has been identified as a molecular marker for distinct subsets of chemoresistant tumor-initiating cell populations in diverse human malignancies. In the current study, we examined the potential role of ABCB5 in growth and chemoresistance of GBM. We found ABCB5 to be preferentially expressed in clinical GBM tumors and co-expressed with the stem cell marker CD133 in subpopulations of human GBM cell lines U-87 MG, LN-18 and LN-229. Antibody-mediated functional ABCB5 blockade inhibited proliferation and survival of human GBM cells and sensitized them to temozolomide (TMZ)-induced apoptosis. Likewise, in an in vivo GBM xenograft study in immunodeficient mice, anti-ABCB5 monoclonal antibody treatment inhibited tumor growth and sensitized tumors to TMZ therapy. Mechanistically, we demonstrated that ABCB5 regulates cell cycle checkpoint molecules to revoke drug-induced G2-M arrest and augments drug-mediated cell death. Overall, our data establish ABCB5 as a marker of GBM chemoresistance and point to the potential of ABCB5 targeting in improvement of current GBM therapies.
Project description:Cancer stem cells (CSC) responsible for disease progression and therapeutic resistance have been identified in several human malignancies, including colorectal cancer (CRC). However, the molecular mechanisms through which CSC drive tumor growth are incompletely understood. ABCB5, a member of the ATP-binding cassette superfamily of active transporters, serves as a CSC-specific multidrug resistance mechanism in diverse human malignancies. Additionally, ABCB5 has recently been demonstrated to function as an anti-apoptotic gene in tissue-specific non-malignant stem cells. Here we demonstrate that ABCB5 also serves an anti-apoptotic role required for CSC maintenance in human cancer. Targeted inhibition of ABCB5, previously shown to be preferentially expressed on CD133-positive CRC stem cells, induced tumor cell apoptosis in vitro and in vivo and inhibited human CRC growth in NSG recipient mice. Mechanistically, ABCB5-positive tumor cell ablation through monoclonal antibody-mediated blockade or shRNA-mediated gene knockdown resulted in diminished production of the receptor tyrosine kinase AXL, a pro-tumorigenic molecule identified herein to be preferentially produced by CRC stem cells. Restoration of AXL expression through gene transfection in ABCB5 knockdown tumors partially restored tumor growth, demonstrating that ABCB5-positive CRC stem cells drive tumorigenicity at least in part through production of AXL. Our results establish a novel anti-apoptotic function of ABCB5 in human cancer and indicate that targeted blockade of ABCB5 represents a novel strategy for CSC eradication, independent of its previously established function as a multidrug resistance mediator.
Project description:Functional analysis of ABCB5 in A375 and G3361 melanoma cells, by comparing stably-transfected controls to ABCB5-shRNA-targeted cells. 12 samples total. Replicates n=3 for the following 4 groups: A375 pSUPER-retro-puro-Vector vs. A375 pSUPER-retro-puro-ABCB5-KD; G3361 pSUPER-retro-puro-shCNTRL vs. G3361 pSUPER-retro-puro-ABCB5-KD.
Project description:Functional analysis of ABCB5 in A375 and G3361 melanoma cells, by comparing stably-transfected controls to ABCB5-shRNA-targeted cells.
Project description:Circulating Tumour Cells (CTCs) act as tumour seeds for haematogeneous melanoma spread of melanoma. Since CTCs have been reported to be heterogeneous in melanoma, the characterisation of the different melanoma CTC subpopulations harbours biological and clinical significance. For detection of melanoma CTCs, melanoma-associated markers (i.e. MCSP, melanoma-associated chondroitin sulphate proteoglycan) have been used; however, recent studies have found that melanoma CTCs commonly express ABCB5 (ATP-binding cassette sub-family B member 5) a melanoma-initiating marker. Here, we used a genome-wide expression microarray to interrogate the transcriptome of MCSP-enriched and ABCB5-enriched CTC fraction in order to provide a better understanding of their biology and role in melanoma metastasis. Findings from this study highlited the distinct transcriptional programming of both CTC subpopulations.
Project description:ABCB5 is marker for Limbal epithilal stem cells. A comparison between ABCB5+ versus ABCB5- cultured human limbal epithelial cells was carried out to evaluate the properties of the limbal stem cell ABCB5+ with a special focus on their role in inflammation and angiogenesis.