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Sensitization of FOLFOX-resistant colorectal cancer cells via the modulation of a novel pathway involving protein phosphatase 2A.

ABSTRACT: The treatment of colorectal cancer (CRC) with FOLFOX shows some efficacy, but these tumors quickly develop resistance to this treatment. We have observed increased phosphorylation of AKT1/mTOR/4EBP1 and levels of p21 in FOLFOX-resistant CRC cells. We have identified a small molecule, NSC49L, that stimulates protein phosphatase 2A (PP2A) activity, downregulates the AKT1/mTOR/4EBP1-axis, and inhibits p21 translation. We have provided evidence that NSC49L- and TRAIL-mediated sensitization is synergistically induced in p21-knockdown CRC cells, which is reversed in p21-overexpressing cells. p21 binds with procaspase 3 and prevents the activation of caspase 3. We have shown that TRAIL induces apoptosis through the activation of caspase 3 by NSC49L-mediated downregulation of p21 translation, and thereby cleavage of procaspase 3 into caspase 3. NSC49L does not affect global protein synthesis. These studies provide a mechanistic understanding of NSC49L as a PP2A agonist, and how its combination with TRAIL sensitizes FOLFOX-resistant CRC cells.

SUBMITTER: Narayan S

PROVIDER: S-EPMC9218363 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Sensitization of FOLFOX-resistant colorectal cancer cells via the modulation of a novel pathway involving protein phosphatase 2A.

Narayan Satya S Raza Asif A Mahmud Iqbal I Koo Nayeong N Garrett Timothy J TJ Law Mary E ME Law Brian K BK Sharma Arun K AK

iScience 20220603 7

The treatment of colorectal cancer (CRC) with FOLFOX shows some efficacy, but these tumors quickly develop resistance to this treatment. We have observed increased phosphorylation of AKT1/mTOR/4EBP1 and levels of p21 in FOLFOX-resistant CRC cells. We have identified a small molecule, NSC49L, that stimulates protein phosphatase 2A (PP2A) activity, downregulates the AKT1/mTOR/4EBP1-axis, and inhibits p21 translation. We have provided evidence that NSC49L- and TRAIL-mediated sensitization is synerg ...[more]

PMID: 35754740

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Project description:Background/aimsProtein phosphatase 2A (PP2A) is a ubiquitous serine/threonine phosphatase that mediates cell cycle regulation and metabolism. Mounting evidence has indicated that PP2A inhibition exhibits considerable anticancer potency in multiple types of human cancers. However, the efficacy of PP2A inhibition remains unexplored in mucoepidermoid carcinoma (MEC), especially in locally advanced and metastatic cases with limited systemic treatment. In this study, we demonstrated the therapeutic potency of LB100 in mucoepidermoid carcinoma.MethodsIn this study, the expression of PP2A was evaluated using immunohistochemical (IHC) staining. The effects associated with LB100 alone and in combination with cisplatin for the treatment of mucoepidermoid carcinoma were investigated both in vitro, regarding metabolism, proliferation, and migration, and in vivo in a mucoepidermoid carcinoma xenograft model. In addition, with LB100 treatment and in response to an insulin stimulus, the expression levels and phosphorylation levels of targets in the PI3K-AKT pathway were determined using western blot analysis and immunoblotting.ResultsThe expression of protein phosphatase 2A was significantly upregulated in the clinical specimens of high-grade MECs compared with those of low-/medium-grade MECs and normal controls. In this article, we report that a small molecule PP2A inhibitor, LB100, decreased cellular viability and glycolytic activity and induced G2/M cell cycle arrest. Importantly, LB100 enhanced the efficacy of cisplatin in mucoepidermoid carcinoma cells both in vitro and in vivo. PP2A inhibition by LB100 increased the phosphorylation of insulin receptor substrate 1(IRS-1) on serine residues, downregulated the expression of phosphatidylinositol 3-kinase (PI3K) p110 alpha subunit and dephosphorylated AKT at Ser473 and Thr308 in mucoepidermoid carcinoma cells in response to insulin stimulus.ConclusionThese results highlight the translational potential of PP2A inhibition to synergize with cisplatin in mucoepidermoid carcinoma treatment.

Project description:BackgroundFOLFOX is the recommended chemotherapy regimen for colorectal cancer (CRC), but its response rate remains low. Our previous studies have established a close relationship between gut microbiota and the anti-CRC effect of FOLFOX, though the underlying mechanisms remain unclear. Diet has been confirmed as a key factor influencing gut microbiota, and high-salt diets, representative of western dietary habits, has been shown to affect gut microbiota, immune function, and the risk of developing CRC. However, the impact of high-salt diets on the anti-CRC efficacy of FOLFOX remains unstudied. Therefore, we aimed to investigate the effect and mechanism of high-salt diets on the anti-CRC effect of FOLFOX.MethodsWe performed 16 S rRNA sequencing and T500 targeted metabolomics analysis on fecal samples from CRC patients and healthy adults. A CRC orthotopic xenograft mouse model was used to study the effect of a high-salt diet on FOLFOX's anti-CRC efficacy. 16 S rRNA sequencing and non-targeted metabolomics were conducted on mouse fecal samples. Flow cytometry was used to assess immune cell infiltration in tumor and paracancerous tissues. A mouse macrophage conditioned medium system, with tryptophan metabolites, was employed to annotate the functional metabolites, followed by in vivo verification using the orthotopic xenograft mouse model.ResultsThe structure and metabolic profiles of gut microbiota are significantly different between 9 healthy adults and 6 CRC patients. A high-salt diet significantly reduced the efficacy of FOLFOX in mice, with notable changes in gut microbiota and related metabolites. Correlation analysis revealed a significant relationship between gut microbiota, tryptophan metabolites and FOLFOX efficacy. Flow cytometry indicated that a high-salt diet altered macrophage infiltration (CD45+F4/80+) in both the tumor and paracancerous tissues. In vitro experiments confirmed that the tryptophan metabolite SK reduced FOLFOX efficacy, while IPA enhanced it through macrophage-conditioned medium. In vivo, we verified that under a high-salt diet, SK inhibited the efficacy of FOLFOX, while IPA promoted it.ConclusionA high-salt diet reduces the anti-CRC efficacy of FOLFOX through gut bacterial tryptophan metabolism mediated macrophage immunomodulation.

Dataset Information

Sensitization of FOLFOX-resistant colorectal cancer cells via the modulation of a novel pathway involving protein phosphatase 2A.

Publications

Sensitization of FOLFOX-resistant colorectal cancer cells via the modulation of a novel pathway involving protein phosphatase 2A.

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