Global proteomic profiling identifies etoposide chemoresistance markers in non-small cell lung carcinoma

• First comprehensive proteomic report on etoposide markers in lung cancer cell NCI-H460
• Multiple proteomic approaches were used to study the etoposide effect on lung cancer cell lines.
• 83 differential expressed proteins involved in chemoresistance have been reported.
• Western blotting, MRM assay and RT-PCR validation supported the proteomic data.
• Functional studies of RHOC and DLG5 evidenced the role in chemoresistance.

Chemoresistance is one of the leading health concerns in cancer treatment. Understanding the mechanism of chemoresistance is the best way to improve the survival of the patient. Etoposide and its analogues are widely used as antitumor drugs in lung cancer but many etoposide resistant lung cancer cases has been identified in recent years. The present study aims to explore the cellular response of lung cancer cell lines to etoposide and finding the potential chemoresistant marker proteins. Multiple proteomic platforms like 2-DE, DIGE and iTRAQ have been used to study the global proteome profile of NCI-H460 and etoposide resistant NCI-H460R cell lines. Our study revealed that etoposide treatment leads to alteration of 83 proteins in NCI-H460R cell lines. The functional analysis highlighted the role of the differential expressed proteins in cellular signaling, apoptosis, and cytoskeleton reorganization. Our study has identified several new proteins like RHOC, DLG5, UGDH, TMOD3 in addition to known chemoresistance associated proteins. In silico prediction of the important selected candidates are further validated at protein and mRNA level. Further, functional studies of newly identified candidate genes RHOC and DLG5 revealed that chemotherapeutic resistance is associated with their elevated level and may serve as novel targets for therapeutic intervention.Biological significanceEtoposide and its analogues have been used for lung cancer treatment for a while and it was reported that many non small cell lung carcinoma patients are resistant to etoposide. Although etoposide show drug resistance, the exact mechanism was not well understood. The present study focused on the global proteome analysis of NCI-H460 and NCI-H460R cell lines using multiple proteomic platforms to understand the potential chemoresistant markers for etoposide. Our multi-proteomic analysis has showed differential expression of 83 proteins involved in oxidative phosphorylation, metabolic, protein folding, cytoskeleton associated protein along with apoptotic pathway has been identified. In addition, quite a few interesting proteins such as RHOC, DLG5, HSP90, citrate synthase, UDP-glucose-6-dehydrogenase, Tropomodulin-3 are involved in chemoresistance has been observed. Overall, this is the first comprehensive proteomic study on etoposide resistant cell line NCI-H460 to explore the mechanism of chemoresistance in lung cancer.

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