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Pharmacological Inhibition of PP2A Overcomes Nab-Paclitaxel Resistance by Downregulating MCL1 in Esophageal Squamous Cell Carcinoma (ESCC).

ABSTRACT: Paclitaxel-based chemotherapy is a treatment option for advanced esophageal squamous cell carcinoma (ESCC). However, the development of chemoresistance leads to treatment failure, and the underlying mechanism remains elusive. We investigated the mechanisms of nanoparticle albumin-bound paclitaxel (nab-PTX) resistance by establishing three nab-PTX resistant ESCC cell lines. Proteomics analysis revealed higher oxidative phosphorylation (OXPHOS) in resistant cell line DR150 than in its parental cell line KYSE150, which is likely caused by stabilized anti-apoptotic protein MCL1. Additionally, we discovered the elevated activity of protein phosphatase 2A (PP2A), the phosphatase that dephosphorylates and stabilizes MCL1, in nab-PTX resistant cell lines. Pharmacological inhibition of PP2A with small molecule compound LB-100 decreased MCL1 protein level, caused more apoptosis in nab-PTX resistant ESCC cell lines than in the parental cells in vitro, and significantly inhibited the tumor growth of nab-PTX resistant xenografts in vivo. Moreover, LB-100 pretreatment partially restored nab-PTX sensitivity in the resistant cell lines and synergistically inhibited the tumor growth of nab-PTX resistant xenografts with nab-PTX. In summary, our study identifies a novel mechanism whereby elevated PP2A activity stabilizes MCL1 protein, increases OXPHOS, and confers nab-PTX resistance, suggesting that targeting PP2A is a potential strategy for reversing nab-PTX resistance in patients with advanced ESCC.

SUBMITTER: Song Q

PROVIDER: S-EPMC8507542 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:MicroRNAs (miRNAs) are an endogenous conserved class of non-coding 20–22 nt small RNAs that regulate gene expression at post-transcriptional level by mostly binding to 3′-UTR of target mRNAs, leading to mRNA degradation or translation inhibition. Recent reports demonstrate a role for miRNA expression in the disease progression and outcome. By now, many researcher focusing on miRNA expression profiles in Barrett's esophagus and esophageal adenocarcinoma have been reported. Nevertheless, there is still a little information available about specific miRNA expression pattern and their roles in ESCC. To develop novel diagnostic and therapeutic targets for esophageal squamous cancer, we first investigated the expression profile of miRNA in three pairs of ESCC clinical samples. Tissues of ESCC and the matched normal counterparts were obtained from surgical specimens immediately after resection from patients undergoing primary surgical treatment of esophageal carcinoma from the Department of Tumor Surgery of Shantou Central Hospital, China. RNA labeling and hybridization were completed by KangChen Bio-tech Inc. (Shanghai, China) according to the manufacturer's instructions. Briefly, total RNA from three pairs of esophageal carcinoma and matched normal tissues were isolated by Trizol (Invitrogen, USA) and purified by RNeasy mini kit (QIAGEN, German). The concentration and quality of total RNA were measured by NanoDrop ND-1000 at 260 and 280 nm (A260/280) and checked by gel electrophoresis. Each RNA sample from three pairs of ESCC was separately labeled either using the miRCURY Hy3/Hy5 labeling kit and hybridized on the six miRCURYTM locked nucleic acid (LNA) array version 11.0 (Exiqon, Denmark), which contains probes for 1700 mature miRNA. Scans were quantified by using GenePix software (Molecular Devices). The data were exported to Microsoft Excel worksheets, log2 transformed, normalized using global Lowess (Locally Weighted Scatter plot Smoothing) regression algorithm (MIDAS, TIGR Microarray Data Analysis System).

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Pharmacological Inhibition of PP2A Overcomes Nab-Paclitaxel Resistance by Downregulating MCL1 in Esophageal Squamous Cell Carcinoma (ESCC).

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