Dataset Information

PKC? is required for Akt-mTORC1 activation in non-small cell lung carcinoma (NSCLC) with EGFR mutation.

ABSTRACT: Mutational activation of the epidermal growth factor receptor (EGFR) is a major player in the pathogenesis of non-small cell lung cancer (NSCLC). NSCLC patients with constitutively active EGFR mutations eventually develop drug resistance against EGFR tyrosine-kinase inhibitors; therefore, better understandings of key components of mutant EGFR (mtEGFR) signaling are required. Here, we initially observed aberrantly high expression of protein kinase C? (PKC?) in lung adenocarcinomas, especially those with EGFR mutations, and proceeded to examine the role of PKC? in the regulation of the signaling pathways downstream of mtEGFR. The results showed that NSCLC cell lines with constitutively active EGFR mutations tend to have very or moderately high PKC? levels. Furthermore, PKC? was constitutively activated in HCC827 and H4006 cells which have an EGFR deletion mutation in exon 19. Interestingly, mtEGFR was not required for the induction of PKC? at protein and message levels suggesting that the increased levels of PKC? are due to independent selection. On the other hand, mtEGFR activity was required for robust activation of PKC?. Loss of functions studies revealed that the NSCLC cells rely heavily on PKC? for the activation of the mTORC1 signaling pathway. Unexpectedly, the results demonstrated that PKC? was required for activation of Akt upstream of mTOR but only in cells with the mtEGFR and with the increased expression of PKC?. Functionally, inhibition of PKC? in HCC827 led to caspase-3-dependent apoptosis and a significant decrease in cell survival in response to cellular stress induced by serum starvation. In summary, the results identified important roles of PKC? in regulating mTORC1 activity in lung cancer cells, whereby a primary switching occurs from PKC?-independent to PKC?-dependent signaling in the presence of EGFR mutations. The results present PKC? as a potential synergistic target of personalized treatment for NSCLC with constitutively active mutant forms of EGFR and constitutively active PKC?.

SUBMITTER: Salama MF

PROVIDER: S-EPMC6883150 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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PKCα is required for Akt-mTORC1 activation in non-small cell lung carcinoma (NSCLC) with EGFR mutation.

Salama Mohamed F MF Liu Mengling M Clarke Christopher J CJ Espaillat Mel Pilar MP Haley John D JD Jin Ting T Wang Daifeng D Obeid Lina M LM Hannun Yusuf A YA

Oncogene 20190816 48

Mutational activation of the epidermal growth factor receptor (EGFR) is a major player in the pathogenesis of non-small cell lung cancer (NSCLC). NSCLC patients with constitutively active EGFR mutations eventually develop drug resistance against EGFR tyrosine-kinase inhibitors; therefore, better understandings of key components of mutant EGFR (mtEGFR) signaling are required. Here, we initially observed aberrantly high expression of protein kinase Cα (PKCα) in lung adenocarcinomas, especially tho ...[more]

PMID: 31420605

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Project description:Background Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are standard treatment for advanced non-small cell lung cancer (NSCLC). However, the emergence of EGFR-TKIs resistance poses a big challenge to the treatment. Although several resistant mutations have been identified, our understanding of the mechanisms underlying acquired EGFR-TKIs resistance remains incomplete. This study aimed to identify novel mutations and mechanisms that could contribute to acquired EGFR-TKIs resistance in EGFR mutated NSCLC cells. Methods Erlotinib resistant cells (HCC827/ER cells) were generated from the EGFR mutated NSCLC cell line HCC827, and whole-exome sequencing was performed to identify gene mutations in HCC827/ER cells. The Spred-3 expression was determined using quantitative real-time PCR (qPCR) and Western blotting assays, and the p-p44/42, p44/42, p-Akt and Akt expression was determined using Western blotting. The half maximal inhibitory concentration (IC50 value) was measured using the MTS assay, and cell migration was detected with a Transwell migration assay. Results Whole-exome sequencing identified deletion mutation c.120delG at exon 1 of the Spred-3 gene, resulting in a p.E40fs change in amino acid, in HCC827/ER cells. The Spred-3 expression was much reduced in HCC827/ER cells as compared to the HCC827 cells at both mRNA and protein levels. Knocking out Spred-3 in HCC827 cells using CRISPR/Cas9 increased erlotinib resistance and cell migration, while overexpressing Spred-3 in HCC827/ER cells using a cDNA construct reduced erlotinib resistance and cell migration. We also showed the Ras/Raf/MAPK pathway was activated in HCC827/ER cells, and inhibiting ERK1/2 in HCC827/Spred-3-sgRNA cells resulted in reduced erlotinib resistance and cell migration. Conclusions The results of this study indicate that a loss-of-function mutation in Spred-3 resulted in activation of the Ras/Raf/MAPK pathway that confers resistance to EGFR-TKIs in NSCLC cells harboring an EGFR mutation.

Project description:BackgroundCancer-related muscle wasting occurs in most cancer patients. An important regulator of adult muscle mass and function is the Akt-mTORC1 pathway. While Akt-mTORC1 signalling is important for adult muscle homeostasis, it is also a major target of numerous cancer treatments. Which role Akt-mTORC1 signalling plays during cancer cachexia in muscle is currently not known. Here, we aimed to determine how activation or inactivation of the pathway affects skeletal muscle during cancer cachexia.MethodsWe used inducible, muscle-specific Raptor ko (mTORC1) mice to determine the effect of reduced mTOR signalling during cancer cachexia. On the contrary, in order to understand if skeletal muscles maintain their anabolic capacity and if activation of Akt-mTORC1 signalling can reverse cancer cachexia, we generated mice in which we can inducibly activate Akt specifically in skeletal muscles.ResultsWe found that mTORC1 signalling is impaired during cancer cachexia, using the Lewis lung carcinoma and C26 colon cancer model, and is accompanied by a reduction in protein synthesis rates of 57% (P < 0.01). Further reduction of mTOR signalling, as seen in Raptor ko animals, leads to a 1.5-fold increase in autophagic flux (P > 0.001), but does not further increase muscle wasting. On the other hand, activation of Akt-mTORC1 signalling in already cachectic animals completely reverses the 15-20% loss in muscle mass and force (P < 0.001). Interestingly, Akt activation only in skeletal muscle completely normalizes the transcriptional deregulation observed in cachectic muscle, despite having no effect on tumour size or spleen mass. In addition to stimulating muscle growth, it is also sufficient to prevent the increase in protein degradation normally observed in muscles from tumour-bearing animals.ConclusionsHere, we show that activation of Akt-mTORC1 signalling is sufficient to completely revert cancer-dependent muscle wasting. Intriguingly, these results show that skeletal muscle maintains its anabolic capacities also during cancer cachexia, possibly giving a rationale behind some of the beneficial effects observed in exercise in cancer patients.

Dataset Information

PKC? is required for Akt-mTORC1 activation in non-small cell lung carcinoma (NSCLC) with EGFR mutation.

Publications

PKCα is required for Akt-mTORC1 activation in non-small cell lung carcinoma (NSCLC) with EGFR mutation.

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