Dataset Information

Metformin Results in Diametrically Opposed Effects by Targeting Non-Stem Cancer Cells but Protecting Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma.

ABSTRACT: Cancer stem cells (CSCs) have been shown as a distinct population of cancer cells strongly implicated with resistance to conventional chemotherapy. Metformin, the most widely prescribed drug for diabetes, was reported to target cancer stem cells in various cancers. In this study, we sought to determine the effects of metformin on head and neck squamous cell carcinoma (HNSCC). CSCs and non-stem HNSCC cells were treated with metformin and cisplatin alone, and in combination, and cell proliferation levels were measured through MTS assays. Next, potential targets of metformin were explored through computational small molecule binding analysis. In contrast to the reported effects of metformin on CSCs in other cancers, our data suggests that metformin protects HNSCC CSCs against cisplatin in vitro. Treatment with metformin resulted in a dose-dependent induction of the stem cell genes CD44, BMI-1, OCT-4, and NANOG. On the other hand, we observed that metformin successfully decreased the proliferation of non-stem HNSCC cells. Computational drug?protein interaction analysis revealed mitochondrial complex III to be a likely target of metformin. Based on our results, we present the novel hypothesis that metformin targets complex III to reduce reactive oxygen species (ROS) levels, leading to the differential effects observed on non-stem cancer cells and CSCs.

SUBMITTER: Kuo SZ

PROVIDER: S-EPMC6337486 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Metformin Results in Diametrically Opposed Effects by Targeting Non-Stem Cancer Cells but Protecting Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma.

Kuo Selena Z SZ Honda Christine O CO Li Wei Tse WT Honda Thomas K TK Kim Elizabeth E Altuna Xabier X Abhold Eric E Wang-Rodriguez Jessica J Ongkeko Weg M WM

International journal of molecular sciences 20190107 1

Cancer stem cells (CSCs) have been shown as a distinct population of cancer cells strongly implicated with resistance to conventional chemotherapy. Metformin, the most widely prescribed drug for diabetes, was reported to target cancer stem cells in various cancers. In this study, we sought to determine the effects of metformin on head and neck squamous cell carcinoma (HNSCC). CSCs and non-stem HNSCC cells were treated with metformin and cisplatin alone, and in combination, and cell proliferation ...[more]

PMID: 30621095

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Project description:We have an incomplete understanding of the differences between cancer stem cells (CSCs) in human papillomavirus-positive (HPV-positive) and -negative (HPV-negative) head and neck squamous cell cancer (HNSCC). The PI3K pathway has the most frequent activating genetic events in HNSCC (especially HPV-positive driven), but the differential signaling between CSCs and non-CSCs is also unknown. We addressed these unresolved questions using CSCs identified from 10 HNSCC patient-derived xenografts (PDXs). Sored populations were serially passaged in nude mice to evaluate tumorigenicity and tumor recapitulation. The transcription profile of HNSCC CSCs was characterized by mRNA sequencing, and the susceptibility of CSCs to therapy was investigated using an in vivo model. SOX2 transcriptional activity was used to follow the asymmetric division of PDX-derived CSCs. All statistical tests were two-sided. CSCs were enriched by high aldehyde dehydrogenase (ALDH) activity and CD44 expression and were similar between HPV-positive and HPV-negative cases (percent tumor formation injecting ≤ 1x10(3) cells: ALDH(+)CD44(high) = 65.8%, ALDH(-)CD44(high) = 33.1%, ALDH(+)CD44(high) = 20.0%; and injecting 1x10(5) cells: ALDH(-)CD44(low) = 4.4%). CSCs were resistant to conventional therapy and had PI3K/mTOR pathway overexpression (GSEA pathway enrichment, P < .001), and PI3K inhibition in vivo decreased their tumorigenicity (40.0%-100.0% across cases). PI3K/mTOR directly regulated SOX2 protein levels, and SOX2 in turn activated ALDH1A1 (P < .001 013C and 067C) expression and ALDH activity (ALDH(+) [%] empty-control vs SOX2, 0.4% ± 0.4% vs 14.5% ± 9.8%, P = .03 for 013C and 1.7% ± 1.3% vs 3.6% ± 3.4%, P = .04 for 067C) in 013C and 067 cells. SOX2 enhanced sphere and tumor growth (spheres/well, 013C P < .001 and 067C P = .04) and therapy resistance. SOX2 expression prompted mesenchymal-to-epithelial transition (MET) by inducing CDH1 (013C P = .002, 067C P = .01), followed by asymmetric division and proliferation, which contributed to tumor formation. The molecular link between PI3K activation and CSC properties found in this study provides insights into therapeutic strategies for HNSCC. Constitutive expression of SOX2 in HNSCC cells generates a CSC-like population that enables CSC studies.

Project description:Cancer stem cell (CSC) subpopulations within moderately differentiated head and neck cutaneous squamous cell carcinoma (MDHNcSCC) express the components of the renin-angiotensin system (RAS). This study investigated the expression of cathepsins B, D, and G, which constitute bypass loops of the RAS, by CSCs in MDHNcSCC.MethodsImmunohistochemical staining was performed on MDHNcSCC tissue samples from 15 patients to determine the expression of cathepsins B, D, and G. Co-localization of these cathepsins with the embryonic stem cell markers Octamer-binding transcription factor 4 (OCT4) and c-MYC was investigated with immunofluorescence staining. Reverse transcription quantitative polymerase chain reaction was performed on 5 MDHNcSCC tissue samples to investigate transcript expression of cathepsins B, D and G. Western blotting and enzymatic activity assays were performed on 5 MDHNcSCC tissue samples and 6 MDHNcSCC-derived primary cell lines to confirm protein expression, transcript expression, and functional activity of these cathepsins, respectively.ResultsImmunohistochemical staining demonstrated the expression of cathepsins B, D, and G in all MDHNcSCC tissue samples. Immunofluorescence staining showed localization of cathepsins B and D to the c-MYC+ CSC subpopulations and the OCT4+ CSC subpopulations within the tumor nests and the peritumoral stroma. Cathepsin G was expressed on the tryptase+/c-MYC+ cells within the peritumoral stroma. Reverse transcription quantitative polymerase chain reaction demonstrated transcript expression of cathepsins B, D and G in the MDHNcSCC tissue samples. Western blotting and enzymatic activity assays confirmed protein expression and functional activity of cathepsins B and D in the MDHNcSCC tissue samples and MDHNcSCC-derived primary cell lines, respectively.ConclusionsCathepsins B, D, and G are expressed in MDHNcSCC with functionally active cathepsins B and D localizing to the CSC subpopulations, and cathepsin G is expressed by mast cells, suggesting the potential use of cathepsin inhibitors in addition to RAS blockade to target CSCs in MDHNcSCC.

Dataset Information

Metformin Results in Diametrically Opposed Effects by Targeting Non-Stem Cancer Cells but Protecting Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma.

Publications

Metformin Results in Diametrically Opposed Effects by Targeting Non-Stem Cancer Cells but Protecting Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma.

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