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Merkel Cell Polyomavirus Small T Antigen Promotes Pro-Glycolytic Metabolic Perturbations Required for Transformation

View Article: PubMed Central - PubMed

ABSTRACT

Merkel cell polyomavirus (MCPyV) is an etiological agent of Merkel cell carcinoma (MCC), a highly aggressive skin cancer. The MCPyV small tumor antigen (ST) is required for maintenance of MCC and can transform normal cells. To gain insight into cellular perturbations induced by MCPyV ST, we performed transcriptome analysis of normal human fibroblasts with inducible expression of ST. MCPyV ST dynamically alters the cellular transcriptome with increased levels of glycolytic genes, including the monocarboxylate lactate transporter SLC16A1 (MCT1). Extracellular flux analysis revealed increased lactate export reflecting elevated aerobic glycolysis in ST expressing cells. Inhibition of MCT1 activity suppressed the growth of MCC cell lines and impaired MCPyV-dependent transformation of IMR90 cells. Both NF-κB and MYC have been shown to regulate MCT1 expression. While MYC was required for MCT1 induction, MCPyV-induced MCT1 levels decreased following knockdown of the NF-κB subunit RelA, supporting a synergistic activity between MCPyV and MYC in regulating MCT1 levels. Several MCC lines had high levels of MYCL and MYCN but not MYC. Increased levels of MYCL was more effective than MYC or MYCN in increasing extracellular acidification in MCC cells. Our results demonstrate the effects of MCPyV ST on the cellular transcriptome and reveal that transformation is dependent, at least in part, on elevated aerobic glycolysis.

No MeSH data available.


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MCPyV-transformed cells exhibit elevated ECAR and sensitivity to MCT1 inhibitors.A) Anchorage-independent growth of IMR90 PH, PHL, PHE and PHEL cells. ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. B) Basal ECAR (mpH/min) measurement of p53DD, PH, PHE and PHE + MYCL (PHEL) cells. **P < 0.005 and ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. C) Proliferation of PHEL cells treated with DMSO, CHC (5 mM), SR13800 (100 nM), or SR13801 (100 nM) was assessed by crystal violet staining. *P < 0.05 calculated using student’s T test between DMSO-SR13800 and DMSO-SR13801 samples. D) Anchorage-independent growth of IMR90 PHE and PHEL cells treated with DMSO, CHC, SR13800 (SR800) or SR13801 (SR801). ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons.
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ppat.1006020.g007: MCPyV-transformed cells exhibit elevated ECAR and sensitivity to MCT1 inhibitors.A) Anchorage-independent growth of IMR90 PH, PHL, PHE and PHEL cells. ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. B) Basal ECAR (mpH/min) measurement of p53DD, PH, PHE and PHE + MYCL (PHEL) cells. **P < 0.005 and ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. C) Proliferation of PHEL cells treated with DMSO, CHC (5 mM), SR13800 (100 nM), or SR13801 (100 nM) was assessed by crystal violet staining. *P < 0.05 calculated using student’s T test between DMSO-SR13800 and DMSO-SR13801 samples. D) Anchorage-independent growth of IMR90 PHE and PHEL cells treated with DMSO, CHC, SR13800 (SR800) or SR13801 (SR801). ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons.

Mentions: We assessed whether MCPyV-mediated transformation could be attenuated by MCT1 inhibition. We found that overexpression of MYCL in PHE (PHEL) IMR90 cells led to robust IMR90 anchorage-independent growth in soft agar, while PH, PHL and PHE cells lacked significant colony formation (Fig 7A). We chose MYCL in this context as it was previously shown that MYCL is amplified in MCC tumors, and may therefore have oncogenic potential in the presence of MCPyV [40]. We measured basal ECAR of IMR90 cells stably expressing p53DD, PH, PHE and PHEL (Fig 7B) and found that PH, PHE and PHEL cells had significantly higher ECAR than p53DD cells, with PHE cells maintaining the highest rate while PHEL cells had a significantly lower ECAR than PHE cells.


Merkel Cell Polyomavirus Small T Antigen Promotes Pro-Glycolytic Metabolic Perturbations Required for Transformation
MCPyV-transformed cells exhibit elevated ECAR and sensitivity to MCT1 inhibitors.A) Anchorage-independent growth of IMR90 PH, PHL, PHE and PHEL cells. ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. B) Basal ECAR (mpH/min) measurement of p53DD, PH, PHE and PHE + MYCL (PHEL) cells. **P < 0.005 and ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. C) Proliferation of PHEL cells treated with DMSO, CHC (5 mM), SR13800 (100 nM), or SR13801 (100 nM) was assessed by crystal violet staining. *P < 0.05 calculated using student’s T test between DMSO-SR13800 and DMSO-SR13801 samples. D) Anchorage-independent growth of IMR90 PHE and PHEL cells treated with DMSO, CHC, SR13800 (SR800) or SR13801 (SR801). ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons.
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ppat.1006020.g007: MCPyV-transformed cells exhibit elevated ECAR and sensitivity to MCT1 inhibitors.A) Anchorage-independent growth of IMR90 PH, PHL, PHE and PHEL cells. ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. B) Basal ECAR (mpH/min) measurement of p53DD, PH, PHE and PHE + MYCL (PHEL) cells. **P < 0.005 and ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons. C) Proliferation of PHEL cells treated with DMSO, CHC (5 mM), SR13800 (100 nM), or SR13801 (100 nM) was assessed by crystal violet staining. *P < 0.05 calculated using student’s T test between DMSO-SR13800 and DMSO-SR13801 samples. D) Anchorage-independent growth of IMR90 PHE and PHEL cells treated with DMSO, CHC, SR13800 (SR800) or SR13801 (SR801). ****P < 0.0001 calculated using ordinary one-way ANOVA with multiple comparisons.
Mentions: We assessed whether MCPyV-mediated transformation could be attenuated by MCT1 inhibition. We found that overexpression of MYCL in PHE (PHEL) IMR90 cells led to robust IMR90 anchorage-independent growth in soft agar, while PH, PHL and PHE cells lacked significant colony formation (Fig 7A). We chose MYCL in this context as it was previously shown that MYCL is amplified in MCC tumors, and may therefore have oncogenic potential in the presence of MCPyV [40]. We measured basal ECAR of IMR90 cells stably expressing p53DD, PH, PHE and PHEL (Fig 7B) and found that PH, PHE and PHEL cells had significantly higher ECAR than p53DD cells, with PHE cells maintaining the highest rate while PHEL cells had a significantly lower ECAR than PHE cells.

View Article: PubMed Central - PubMed

ABSTRACT

Merkel cell polyomavirus (MCPyV) is an etiological agent of Merkel cell carcinoma (MCC), a highly aggressive skin cancer. The MCPyV small tumor antigen (ST) is required for maintenance of MCC and can transform normal cells. To gain insight into cellular perturbations induced by MCPyV ST, we performed transcriptome analysis of normal human fibroblasts with inducible expression of ST. MCPyV ST dynamically alters the cellular transcriptome with increased levels of glycolytic genes, including the monocarboxylate lactate transporter SLC16A1 (MCT1). Extracellular flux analysis revealed increased lactate export reflecting elevated aerobic glycolysis in ST expressing cells. Inhibition of MCT1 activity suppressed the growth of MCC cell lines and impaired MCPyV-dependent transformation of IMR90 cells. Both NF-&kappa;B and MYC have been shown to regulate MCT1 expression. While MYC was required for MCT1 induction, MCPyV-induced MCT1 levels decreased following knockdown of the NF-&kappa;B subunit RelA, supporting a synergistic activity between MCPyV and MYC in regulating MCT1 levels. Several MCC lines had high levels of MYCL and MYCN but not MYC. Increased levels of MYCL was more effective than MYC or MYCN in increasing extracellular acidification in MCC cells. Our results demonstrate the effects of MCPyV ST on the cellular transcriptome and reveal that transformation is dependent, at least in part, on elevated aerobic glycolysis.

No MeSH data available.


Related in: MedlinePlus