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Restoration of MARCKS enhances chemosensitivity in cancer.

ABSTRACT: PURPOSE:Increased ATP-binding-cassette (ABC) transporter activity is a major cause of chemotherapy resistance in cancer. The ABC transporter family member ABCB1 is often overexpressed in colorectal cancer (CRC). Phosphatidylinositol-4,5-bisphosphat (PI(4,5)P2)-dependent pathways are involved in the regulation of ABCB1 function. The protein Myristoylated Alanine-Rich C-Kinase Substrate (MARCKS) is a pivotal regulator of PI(4,5)P2 and inactivated in many CRC cancers via genetic deletion or hyperphosphorylation. Therefore, MARCKS may critically impact ABCB1. METHODS:CRC samples as well as CRC cell lines were tested for a connection between MARCKS and ABCB1 via immunofluorescence and Western-blot analysis. ABCB1 function was studied via calcein influx assay under treatment with known ABCB1 inhibitors (verapamil, tariquidar) as well as the kinase inhibitor bosutinib. ABCB1 internalization and MARCKS translocation was analyzed via confocal microscopy exploiting the endocytosis inhibitors chlorpromazine and dynasore. Abundance of PI(4,5)P2 was monitored by intramolecular fluorescence resonance energy transfer (FRET). Reproductive cell survival was studied via colorimetric WST-1 and clonogenic assays in combination with exposure to the chemotherapeutics doxorubicin and 5-fuorouracil (5-FU). RESULTS:We found increased ABCB1 expression in MARCKS negative CRC patient tumor samples and established CRC cell lines. Mechanistically, the reconstitution of MARCKS function via recombinant expression or the pharmacological inhibition of MARCKS phosphorylation led to a substantial decrease in ABCB1 activity. In CRC cells, bosutinib treatment resulted in a MARCKS translocation from the cytosol to the plasma membrane, while simultaneously, ABCB1 was relocated to intracellular compartments. Inhibition of MARCKS phosphorylation via bosutinib rendered cells more sensitive to the chemotherapeutics doxorubicin and 5-FU. CONCLUSIONS:Cells devoid of MARCKS function showed incomplete ABCB1 internalization, leading to higher ABCB1 activity enhancing chemoresistance. Vice versa our data suggest the prevention of MARCKS inhibition by reversing hyperphosphorylation or genomic restoration after deletion as two promising approaches to overcome tumor cell resistance towards chemotherapeutic ABCB1 substrates.

SUBMITTER: Wenzel T

PROVIDER: S-EPMC7085482 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Restoration of MARCKS enhances chemosensitivity in cancer.

Wenzel Tim T Büch Thomas T Urban Nicole N Weirauch Ulrike U Schierle Katrin K Aigner Achim A Schaefer Michael M Kalwa Hermann H

Journal of cancer research and clinical oncology 20200213 4

<h4>Purpose</h4>Increased ATP-binding-cassette (ABC) transporter activity is a major cause of chemotherapy resistance in cancer. The ABC transporter family member ABCB1 is often overexpressed in colorectal cancer (CRC). Phosphatidylinositol-4,5-bisphosphat (PI(4,5)P<sub>2</sub>)-dependent pathways are involved in the regulation of ABCB1 function. The protein Myristoylated Alanine-Rich C-Kinase Substrate (MARCKS) is a pivotal regulator of PI(4,5)P<sub>2</sub> and inactivated in many CRC cancers v ...[more]

PMID: 32056006

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Project description:Colon cancer is one of the most common cancers in the world. Multidrug resistance is one of the main reasons for failure of therapy in patients with advanced colon cancer. In previous studies, multiple methods were investigated to reverse the multidrug resistance of colon cancer cells. However, to date, no clinical method has been identified to be satisfactory. Therefore, successful reversal of drug resistance in colon cancer cells still requires new therapeutic strategies or pharmaceuticals. Wild-type p53-induced phosphatase (Wip1), a member of the 2C type serine/threonine protein phosphatase family, is closely associated with the p53 gene, which is the most important tumor-suppressor gene. Wip1 was reported to be associated with the chemosensitivity of breast cancer cells. However, the correlation between the expression of Wip1 gene and the chemosensitivity of colon cancer cells has not been reported yet. In the present study, Wip1-811 small interfering RNA (siRNA) targeting Wip1 was investigated to reverse the multidrug resistance of colon cancer cells. The siRNA duplexes were transfected into RKO colon cancer cells. The messenger RNA (mRNA) expression of Wip1 was measured by reverse transcription-quantitative polymerase chain reaction. The protein level of Wip1 was detected by western blotting. The cell viability was measured by MTS assay. The cell apoptosis and cell cycle were analyzed by flow cytometry. Intracellular adriamycin cumulative concentration was determined using flow cytometry. Wip1-811 siRNA efficiently inhibited the expression of Wip1 at the mRNA and protein levels, and enhanced the sensitivity of RKO colon cancer cells towards chemotherapy, which was accompanied by increased cell apoptosis, following the inhibition of Wip1 gene expression. These results indicate that Wip1 gene silencing could enhance the chemosensitivity of colon cancer cells, which may provide a new potential approach for the reversal of multidrug resistance in colon cancer cells.

Project description:BACKGROUND:Protein kinase C theta, (PRKCQ/PKC?) is a serine/threonine kinase that is highly expressed in a subset of triple-negative breast cancers (TNBC) and promotes their growth, anoikis resistance, epithelial-mesenchymal transition (EMT), and invasion. Here, we show that PRKCQ regulates the sensitivity of TNBC cells to apoptosis triggered by standard-of-care chemotherapy by regulating levels of pro-apoptotic Bim. METHODS:To determine the effects of PRKCQ expression on chemotherapy-induced apoptosis, shRNA and cDNA vectors were used to modulate the PRKCQ expression in MCF-10A breast epithelial cells or triple-negative breast cancer cells (MDA-MB231Luc, HCC1806). A novel PRKCQ small-molecule inhibitor, 17k, was used to inhibit kinase activity. Viability and apoptosis of cells treated with PRKCQ cDNA/shRNA/inhibitor +/-chemotherapy were measured. Expression levels of Bcl2 family members were assessed. RESULTS:Enhanced expression of PRKCQ is sufficient to suppress apoptosis triggered by paclitaxel or doxorubicin treatment. Downregulation of PRKCQ also enhanced the apoptosis of chemotherapy-treated TNBC cells. Regulation of chemotherapy sensitivity by PRKCQ mechanistically occurs via regulation of levels of Bim, a pro-apoptotic Bcl2 family member; suppression of Bim prevents the enhanced apoptosis observed with combined PRKCQ downregulation and chemotherapy treatment. Regulation of Bim and chemotherapy sensitivity is significantly dependent on PRKCQ kinase activity; overexpression of a catalytically inactive PRKCQ does not suppress Bim or chemotherapy-associated apoptosis. Furthermore, PRKCQ kinase inhibitor treatment suppressed growth, increased anoikis and Bim expression, and enhanced apoptosis of chemotherapy-treated TNBC cells, phenocopying the effects of PRKCQ downregulation. CONCLUSIONS:These studies support PRKCQ inhibition as an attractive therapeutic strategy and complement to chemotherapy to inhibit the growth and survival of TNBC cells.

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Restoration of MARCKS enhances chemosensitivity in cancer.

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Restoration of MARCKS enhances chemosensitivity in cancer.

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