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Synergistic targeting of the PI3K/mTOR and MAPK/ERK pathways in Merkel cell carcinoma.

ABSTRACT: Merkel cell carcinoma (MCC) is an aggressive type of skin cancer, which is caused either by integration of the oncogenic Merkel cell polyomavirus (MCPyV) or by accumulation of UV-light induced mutations. Since the response to immune-checkpoint inhibitors is limited, new therapeutic agents need to be explored. Previous studies have shown that MCC cell lines and xenografts are sensitive to MLN0128, a dual mTOR1/2 inhibitor. Prompted by these results and considering that the PI3K/mTOR and MAPK/ERK pathways are the most commonly deregulated pathways in cancer, the combination of MLN0128 with the MEK1/2 inhibitor trametinib was investigated. Importantly, the combined targeting showed to be synergistic in MCC cell lines and induced alterations in the protein levels of downstream elements of the targeted pathways. This synergistic activity implies a reduction in the dose of each inhibitor necessary to reach the same effect that when used as single agents. Therefore, this is a promising approach to improve the clinical management of MCC and to overcome the limited efficacy of single drug regimens owed to the appearance of toxicity or drug resistance.

SUBMITTER: Temblador A

PROVIDER: S-EPMC9449649 | biostudies-literature | 2022 Dec

REPOSITORIES: biostudies-literature

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Synergistic targeting of the PI3K/mTOR and MAPK/ERK pathways in Merkel cell carcinoma.

Temblador Arturo A Topalis Dimitrios D Andrei Graciela G Snoeck Robert R

Tumour virus research 20220822

Merkel cell carcinoma (MCC) is an aggressive type of skin cancer, which is caused either by integration of the oncogenic Merkel cell polyomavirus (MCPyV) or by accumulation of UV-light induced mutations. Since the response to immune-checkpoint inhibitors is limited, new therapeutic agents need to be explored. Previous studies have shown that MCC cell lines and xenografts are sensitive to MLN0128, a dual mTOR1/2 inhibitor. Prompted by these results and considering that the PI3K/mTOR and MAPK/ERK ...[more]

PMID: 36007768

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Project description:In spite of the promising in vitro and preclinical results, dual PI3K/Akt/mTOR inhibitor NVP-BEZ235, and ATP-competitive mTOR inhibitor PP242 both failed to confirm their inhibitory efficacy against renal cell carcinoma (RCC) in clinical settings. Therefore, a better understanding of the molecular mechanism is essential so as to provide possibilities for their use in combination with other agents. In present study, RCC cell lines (UMRC6, 786-0 and UOK121) were treated with NVP-BEZ235, PP242 or Rapamycin, an mTOR complex 1 (mTORC1)-specific inhibitor. They all suppressed cell proliferation and invasion, induced apoptosis and cell cycle arrest, and the effects were in the order of NVP-BEZ235 > PP242 > Rapamycin. Accordingly, the marked and sustained decrease in speckle-type POZ protein (SPOP) expression and phosphorylation of Akt and mTOR kinases was observed in RCC cells treated with NVP-BEZ235 and PP242, whereas only potent inhibition of mTOR activity was induced in Rapamycin-treated cells. In considering the overactivation of c-Jun and IκB-α in human renal tumor tissue, we next investigated the role of JNK and IKK pathways in the response of RCC cells to these compounds. First of all, transforming growth factor β activated kinase 1 (TAK1)-dependent activation of JNK/ (activator protein-1) AP-1 axis in RCC cells was proved by the repression of AP-1 activity with TAK1 or JNK inhibitor. Second, the profound inhibition of TAK1/JNK/AP-1 pathway was demonstrated in RCC cells treated with NVP-BEZ235 or PP242 but not Rapamycin, which is manifested as a reduction in activity of TAK1, c-Jun and AP-1. Meanwhile, subsequent to TAK1 inactivation, the activation of IκB-α was also reduced by NVP-BEZ235 and PP242. Likewise, in vivo, treatment with NVP-BEZ235 and PP242 suppressed the growth of xenografts generated from 786-0 and A498 cells, along with decreased expression of phospho-TAK1, phospho-c-Jun, and phospho-IκB-α. In contrast, Rapamycin elicited no significant inhibitory effects on tumor growth and phosphorylation of TAK1, c-Jun and IκB-α. We conclude that besides PI3K/Akt/mTOR signaling, NVP-BEZ235, and PP242 simultaneously target TAK1-dependent pathways in RCC cells. Notably, these effects were more marked in the presence of NVP-BEZ235 than PP242, indicating the potential application of NVP-BEZ235 in combination therapy for RCC.

Dataset Information

Synergistic targeting of the PI3K/mTOR and MAPK/ERK pathways in Merkel cell carcinoma.

Publications

Synergistic targeting of the PI3K/mTOR and MAPK/ERK pathways in Merkel cell carcinoma.

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