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Functional significance of the ATP-binding cassette transporter B6 in hepatocellular carcinoma.

ABSTRACT: ABCB6 is a mitochondrial transporter that regulates porphyrin biosynthesis. ABCB6 expression is upregulated in hepatocellular carcinoma (HCC) but the significance of this upregulation to HCC is not known. In the present study, we investigated: 1) ABCB6 expression in 18 resected human hepatocellular carcinoma (HCC) tissues and 3 human hepatoma cell lines; 2) pattern of ABCB6 expression during liver disease progression; and 3) functional significance of ABCB6 expression to HCC using the hepatoma cell line Huh7. ABCB6 expression was determined by real-time quantitative reverse transcription-polymerase chain reaction and western blotting. ABCB6 expression was upregulated in all the HCC specimens and the three-hepatoma cell lines. Increased ABCB6 expression correlated with liver disease progression with the pattern of expression being HCC > cirrhosis > steatosis. Small hairpin RNA (shRNA)-mediated knockdown of ABCB6 in Huh7 cells lead to decreased cellular proliferation and colony formation. Attenuation of ABCB6 expression did not affect Huh7 apoptosis but lead to a delay in G2/M phase of the cell cycle. In contrast, ABCB6 overexpression resulted in increased growth and proliferation of Huh7 cells. Since ABCB6 expression is induced in multiple tumor types we explored the role of ABCB6 in other cancer cells. ShRNA mediated knockdown of ABCB6 in HEK293 and K562 cells reduced cellular proliferation leading to a delay in G2/M phase, while ABCB6 overexpression promoted cell growth and proliferation. Collectively, these findings, obtained by loss of function and gain of function analysis, suggest that ABCB6 plays a role in cell growth and proliferation by targeting the cell cycle.

SUBMITTER: Polireddy K

PROVIDER: S-EPMC3204372 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The purpose of this investigation was to assess the diagnostic and prognostic significance of ATP binding cassette subfamily C (ABCC) genes in hepatocellular carcinoma (HCC). The Student t-test was used to compare the expression level of ABCCs between HCC and paraneoplastic tissues. Receiver operating characteristic curve (ROC) analysis was applied for diagnostic efficiency assessment. The Kaplan-Meier method and Cox proportional hazards model were respectively applied for survival analysis. Genes with prognostic significance were subsequently used to construct prognostic models. From the perspective of genome-wide enrichment analysis, the mechanisms of prognosis-related ABCC genes were attempted to be elaborated by gene set enrichment analysis (GSEA). It was observed in the TCGA database that ABCC1, ABCC4, ABCC5, and ABCC10 were significantly upregulated in tumor tissues, while ABCC6 and ABCC7 were downregulated in HCC tissues. Receiver operating characteristic analysis revealed that ABCC7 might be a potential diagnostic biomarker in HCC. ABCC1, ABCC4, ABCC5, and ABCC6 were significantly related to the prognosis of HCC in the TCGA database. The prognostic significance of ABCC1, ABCC4, ABCC5, and ABCC6 was also observed in the Guangxi cohort. In the Guangxi cohort, both polymerase chain reaction and IHC (immunohistochemical) assays demonstrated higher expression of ABCC1, ABCC4, and ABCC5 in HCC compared to liver tissues, while the opposite was true for ABCC6. GSEA analysis indicated that ABCC1 was associated with tumor differentiation, nod-like receptor signal pathway, and so forth. It also revealed that ABCC4 might play a role in HCC by regulating epithelial-mesenchymal transition, cytidine analog pathway, met pathway, and so forth. ABCC5 might be associated with the fatty acid metabolism and KRT19 in HCC. ABCC6 might impact the cell cycle in HCC by regulating E2F1 and myc. The relationship between ABCC genes and immune infiltration was explored, and ABCC1,4,5 were found to be positively associated with infiltration of multiple immune cells, while ABCC6 was found to be the opposite. In conclusion, ABCC1, ABCC4, ABCC5, and ABCC6 might be prognostic biomarkers in HCC. The prognostic models constructed with ABCC1, ABCC4, ABCC5, and ABCC6 had satisfactory efficacy.

Project description:PurposeLiver cancer is the fifth most common type of cancer worldwide, and the ATP-binding cassette (ABC) transporter family has been widely accepted as a cause of multidrug resistance. This study was conducted to explore the potential value and mechanisms of the ABC transporter gene family in the liver hepatocellular carcinoma (LIHC).Materials and methodsData were collected from different public databases. UALCAN, ONCOMINE, and GEPIA were used to retrieve a selection of differently expressed and pathological stage-related genes among the ABC family. Principal component analysis (PCA) was utilized for grouping, and its prognostic value was evaluated by univariate and multivariate Cox analyses. The co-expression pattern was constructed with UALCAN, and the functional analyses were carried out with DAVID. The correlation between the biomarker and immune infiltration, genetic alteration frequency, and drug sensitivity were explored with TIMER, cBioPortal, GDSC and CTRP, respectively. Finally, tSNE algorithm was used to explore the distribution of ABCC5 expressed cells.ResultsAmong the ABC transporter family members, ABCC5 was differently expressed and strongly related to the pathological stage of LIHC. PCA divided patients of LIHC into two groups, and Cox analyses demonstrated that ABCC5 was an independent risk factor of LIHC. Functional analyses indicated that the genes were enriched in the pathways of transmembrane transporter, ATPase activity, and bile secretion. ABCC5 is also associated with immune infiltration of cells like macrophages, neutrophils, and dendritic cells. The genetic alteration frequency of ABCC5 confirmed its potential value in LIHC. In addition, several drugs were explored and found to be relevant to LIHC. The t-SNE showed that expression of ABCC5 was most concentrated in macrophages, followed by hepatocytes.ConclusionABCC5 may facilitate LIHC progression through different mechanisms and be a potential biomarker and target for diagnosis, prognosis, and therapy of LIHC.

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Functional significance of the ATP-binding cassette transporter B6 in hepatocellular carcinoma.

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