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GPR56 Drives Colorectal Tumor Growth and Promotes Drug Resistance through Upregulation of MDR1 Expression via a RhoA-Mediated Mechanism.

ABSTRACT: Drug resistance continues to be a major obstacle of effective therapy for colorectal cancer, leading to tumor relapse or treatment failure. Cancer stem cells (CSC) or tumor-initiating cells are a subpopulation of tumor cells which retain the capacity for self-renewal and are suggested to be implicated in drug resistance. LGR5 is highly expressed in colorectal cancer and marks CSCs that drive tumor growth and metastasis. LGR5(+) CSCs cells were shown to interconvert with more drug-resistant LGR5(-) cancer cells, and treatment with LGR5-targeted antibody-drug conjugates (ADC) eliminated LGR5(+) tumors, yet a fraction of LGR5(-) tumors eventually recurred. Therefore, it is important to identify mechanisms associated with CSC plasticity and drug resistance in order to develop curative therapies. Here, we show that loss of LGR5 in colon cancer cells enhanced resistance to irinotecan and 5-fluorouracil and increased expression of adhesion G-protein-coupled receptor, GPR56. GPR56 expression was significantly higher in primary colon tumors versus matched normal tissues and correlated with poor survival outcome. GPR56 enhanced drug resistance through upregulation of MDR1 levels via a RhoA-mediated signaling mechanism. Loss of GPR56 led to suppression of tumor growth and increased sensitivity of cancer cells to chemotherapy and monomethyl auristatin E-linked anti-LGR5 ADCs, by reducing MDR1 levels. These findings suggest that upregulation of GPR56 may be a mechanism associated with CSC plasticity by which LGR5(-) cancer cells acquire a more drug-resistant phenotype. IMPLICATIONS: Our findings suggest that targeting GPR56 may provide a new strategy for the treatment of colorectal cancer and combatting drug resistance.

SUBMITTER: Zhang S

PROVIDER: S-EPMC6913243 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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GPR56 Drives Colorectal Tumor Growth and Promotes Drug Resistance through Upregulation of MDR1 Expression via a RhoA-Mediated Mechanism.

Zhang Sheng S Chatterjee Treena T Godoy Carla C Wu Ling L Liu Qingyun J QJ Carmon Kendra S KS

Molecular cancer research : MCR 20190823 11

Drug resistance continues to be a major obstacle of effective therapy for colorectal cancer, leading to tumor relapse or treatment failure. Cancer stem cells (CSC) or tumor-initiating cells are a subpopulation of tumor cells which retain the capacity for self-renewal and are suggested to be implicated in drug resistance. LGR5 is highly expressed in colorectal cancer and marks CSCs that drive tumor growth and metastasis. LGR5(<sup>+</sup>) CSCs cells were shown to interconvert with more drug-resi ...[more]

PMID: 31444231

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Project description:Candida dubliniensis is a recently described opportunistic fungal pathogen that is closely related to Candida albicans. Candida dubliniensis readily develops resistance to the azole antifungal agent fluconazole, both in vitro and in infected patients, and this resistance is usually associated with upregulation of the CdMDR1 gene, encoding a multidrug efflux pump of the major facilitator superfamily. To determine the role of CdMDR1 in drug resistance in C. dubliniensis, we constructed an mdr1 null mutant from the fluconazole-resistant clinical isolate CM2, which overexpressed the CdMDR1 gene. Sequential deletion of both CdMDR1 alleles was performed by the MPA(R)-flipping method, which is based on the repeated use of a dominant mycophenolic acid resistance marker for selection of integrative transformants and its subsequent deletion from the genome by FLP-mediated, site-specific recombination. In comparison with its parental strain, the mdr1 mutant showed decreased resistance to fluconazole but not to the related drug ketoconazole. In addition, we found that CdMDR1 confers resistance to the structurally unrelated drugs 4-nitroquinoline-N-oxide, cerulenin, and brefeldin A, since the enhanced resistance to these compounds of the parent strain CM2 compared with the matched susceptible isolate CM1 was abolished in the mdr1 mutant. In contrast, CdMDR1 inactivation did not cause increased susceptibility to amorolfine, terbinafine, fluphenazine, and benomyl, although overexpression of CdMDR1 in a hypersusceptible Saccharomyces cerevisiae strain had previously been shown to confer resistance to these compounds. The effect of CdMDR1 inactivation was identical to that seen in two similarly constructed C. albicans mdr1 mutants. Therefore, despite species-specific differences in the amino acid sequences of the Mdr1 proteins, overexpression of CaMDR1 and CdMDR1 in clinical C. albicans and C. dubliniensis strains seems to confer the same drug resistance profile in both species.

Dataset Information

GPR56 Drives Colorectal Tumor Growth and Promotes Drug Resistance through Upregulation of MDR1 Expression via a RhoA-Mediated Mechanism.

Publications

GPR56 Drives Colorectal Tumor Growth and Promotes Drug Resistance through Upregulation of MDR1 Expression via a RhoA-Mediated Mechanism.

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