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P62/SQSTM1 is required for cell survival of apoptosis-resistant bone metastatic prostate cancer cell lines.

ABSTRACT: Bone marrow stromal cell (BMSC) paracrine factor(s) can induce apoptosis in bone metastatic prostate cancer (PCa) cell lines. However, the PCa cells that escape BMSC-induced apoptosis can upregulate cytoprotective autophagy.C4-2, C4-2B, MDA PCa 2a, MDA PCa 2b, VCaP, PC3, or DU145 PCa cell lines were grown in BMSC conditioned medium and analyzed for mRNA and/or protein accumulation of p62 (also known as sequestome-1/SQSTM1), Microtubule-associated protein 1 light chain 3B (LC3B), or lysosomal-associated membrane protein 1 (LAMP1) using quantitative polymerase chain reaction (QPCR), Western blot, or immunofluorescence. Small interfering RNA (siRNA) was used to determine if p62 is necessary PCa cell survival.BMSC paracrine signaling upregulated p62 mRNA and protein in a subset of the PCa cell lines. The PCa cell lines that were insensitive to BMSC-induced apoptosis and autophagy induction had elevated basal p62 mRNA and protein. In the BMSC-insensitive PCa cell lines, siRNA knockdown of p62 was cytotoxic and immunostaining showed peri-nuclear clustering of autolysosomes. However, in the BMSC-sensitive PCa cell lines, p62 siRNA knockdown was not appreciably cytotoxic and did not affect autolysosome subcellular localization.A pattern emerges wherein the BMSC-sensitive PCa cell lines are known to be osteoblastic and express the androgen receptor, while the BMSC-insensitive PCa cell lines are characteristically osteolytic and do not express the androgen receptor. Furthermore, BMSC-insensitive PCa may have evolved a dependency on p62 for cell survival that could be exploited to target and kill these apoptosis-resistant PCa cells in the bone.

SUBMITTER: Chang MA

PROVIDER: S-EPMC3877418 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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p62/SQSTM1 is required for cell survival of apoptosis-resistant bone metastatic prostate cancer cell lines.

Chang Megan A MA Morgado Micaela M Warren Curtis R CR Hinton Cimona V CV Farach-Carson Mary C MC Delk Nikki A NA

The Prostate 20130930 2

<h4>Background</h4>Bone marrow stromal cell (BMSC) paracrine factor(s) can induce apoptosis in bone metastatic prostate cancer (PCa) cell lines. However, the PCa cells that escape BMSC-induced apoptosis can upregulate cytoprotective autophagy.<h4>Methods</h4>C4-2, C4-2B, MDA PCa 2a, MDA PCa 2b, VCaP, PC3, or DU145 PCa cell lines were grown in BMSC conditioned medium and analyzed for mRNA and/or protein accumulation of p62 (also known as sequestome-1/SQSTM1), Microtubule-associated protein 1 ligh ...[more]

PMID: 24122957

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Project description:Enzalutamide is a novel antiandrogen with proven efficacy in metastatic castration-resistant prostate cancer (mCRPC).To evaluate enzalutamide's effects on cancer and on androgens in blood and bone marrow, and associate these with clinical observations.In this prospective phase 2 study, 60 patients with bone mCRPC received enzalutamide 160mg orally daily and had transilial bone marrow biopsies before treatment and at 8 wk of treatment.Androgen signaling components (androgen receptor [AR], AR splice variant 7 (ARV7), v-ets avian erythroblastosis virus E26 oncogene homolog [ERG], cytochrome P450, family 17, subfamily A, polypeptide 1 [CYP17]) and molecules implicated in mCRPC progression (phospho-Met, phospho-Src, glucocorticoid receptor, Ki67) were assessed by immunohistochemistry; testosterone, cortisol, and androstenedione concentrations were assessed by liquid chromatography-tandem mass spectrometry; AR copy number was assessed by real-time polymerase chain reaction. Descriptive statistics were applied.Median time to treatment discontinuation was 22 wk (95% confidence interval, 19.9-29.6). Twenty-two (37%) patients exhibited primary resistance to enzalutamide, discontinuing treatment within 4 mo. Maximal prostate-specific antigen (PSA) decline ? 50% and ? 90% occurred in 27 (45%) and 13 (22%) patients, respectively. Following 8 wk of treatment, bone marrow and circulating testosterone levels increased. Pretreatment tumor nuclear AR overexpression (> 75%) and CYP17 (> 10%) expression were associated with benefit (p = 0.018). AR subcellular localization shift from the nucleus was confirmed in eight paired samples (with PSA decline) of 23 evaluable paired samples. Presence of an ARV7 variant was associated with primary resistance to enzalutamide (p = 0.018). Limited patient numbers warrant further validation.The observed subcellular shift of AR from the nucleus and increased testosterone concentration provide the first evidence in humans that enzalutamide suppresses AR signaling while inducing an adaptive feedback. Persistent androgen signaling in mCRPC was predictive of benefit and ARV7 was associated with primary resistance.We report a first bone biopsy study in metastatic prostate cancer in humans that searched for predictors of outcome of enzalutamide therapy. Benefit is linked to a pretreatment androgen-signaling signature.ClinicalTrials.gov identifier NCT01091103.

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P62/SQSTM1 is required for cell survival of apoptosis-resistant bone metastatic prostate cancer cell lines.

Publications

p62/SQSTM1 is required for cell survival of apoptosis-resistant bone metastatic prostate cancer cell lines.

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