MASTL inhibition promotes mitotic catastrophe through PP2A activation to inhibit cancer growth and radioresistance in breast cancer cells

Abstract

BackgroundAlthough MASTL (microtubule-associated serine/threonine kinase-like) is a key mitotic kinase that regulates mitotic progression through the inactivation of tumor suppressor protein phosphatase 2A (PP2A), the antitumor mechanism of MASTL targeting in cancer cells is still unclear.MethodsMASTL expression was evaluated by using breast cancer tissue microarrays and public cancer databases. The effects of MASTL depletion with siRNAs were evaluated in various breast cancer cells or normal cells. Various methods, including cell viability, cell cycle, soft agar, immunoblotting, immunofluorescence, PP2A activity, live image, and sphere forming assay, were used in this study.ResultsThis study showed the oncosuppressive mechanism of MASTL targeting that promotes mitotic catastrophe through PP2A activation selectively in breast cancer cells. MASTL expression was closely associated with tumor progression and poor prognosis in breast cancer. The depletion of MASTL reduced the oncogenic properties of breast cancer cells with high MASTL expression, but did not affect the viability of non-transformed normal cells with low MASTL expression. With regard to the underlying mechanism, we found that MASTL inhibition caused mitotic catastrophe through PP2A activation in breast cancer cells. Furthermore, MASTL depletion enhanced the radiosensitivity of breast cancer cells with increased PP2A activity. Notably, MASTL depletion dramatically reduced the formation of radioresistant breast cancer stem cells in response to irradiation.ConclusionOur data suggested that MASTL inhibition promoted mitotic catastrophe through PP2A activation, which led to the inhibition of cancer cell growth and a reversal of radioresistance in breast cancer cells.Electronic supplementary materialThe online version of this article (10.1186/s12885-018-4600-6) contains supplementary material, which is available to authorized users.

Predicting Radiation Resistance in Breast Cancer with Expression Status of Phosphorylated S6K1

“…2a). Furthermore, we found that CD44 high /CD24 low MCF7 cells, a breast cancer stem cell line with a radioresistant phenotype 24,25 ( Supplementary Fig. S2), expressed higher levels of p-S6K1 compared to those of control MCF7 cells ( Fig.…”

“…All media were supplemented with 10% foetal bovine serum (Corning) and 1% penicillin/streptomycin, and maintained in a humidified 5% CO 2 incubator at 37 °C. Radioresistant CD44 high /CD24 low MCF7 cells were established using a previously described method 24,25 . In brief, CD44 + /CD24 − subpopulations from MCF7 cells were isolated according to their surface markers with flow cytometry using a FACS Aria II system (BD Biosciences, San Diego, CA, USA).…”

“…Clonogenic assay. Cell survival after irradiation was determined by a clonogenic assay as described previously 25,42 . In brief, 500 MCF7 or CD44 high /CD24 low MCF7 cells were seeded in triplicate in 60-mm tissue culture dishes and treated with the indicated conditions without or with 3-or 6-Gy radiation using Biobeam GM8000 (Gamma-Service Medical GmbH, Leipzig, Germany).…”

Barium Titanate Nanoparticles Sensitise Treatment-Resistant Breast Cancer Cells to the Antitumor Action of Tumour-Treating Fields

“…Clonogenic assay. The clonogenic assay was performed as described previously 7,10,35 . MCF-7 or BT-549 cells (500 in number) were seeded on a 22 mm plastic coverslip in a 6-well plate for 24 hrs.…”

“…After this, mean SSC-A value in PI-negative population was quantified and relative Mean SSC-A values were calculated based on none-vehicle. Cell cycle analysis was performed following the method previously described 35 . Briefly, the cells treated with TTFields or TTFields and BTNP for 72 hrs were trypsinized, washed twice in PBS, and fixed with ice-cold 70% ethanol.…”