Cell Stress Induced Stressome Release Including Damaged Membrane Vesicles and Extracellular HSP90 by Prostate Cancer Cells.

Takanori Eguchi,Kuniaki Okamoto,Chiharu Sogawa,Stuart K Calderwood,Yuka Okusha,Manh Tien Tran,Masaki Matsumoto,Kisho Ono,Benjamin J Lang

doi:10.3390/cells9030755

Abstract

Tumor cells exhibit therapeutic stress resistance-associated secretory phenotype involving extracellular vesicles (EVs) such as oncosomes and heat shock proteins (HSPs). Such a secretory phenotype occurs in response to cell stress and cancer therapeutics. HSPs are stress-responsive molecular chaperones promoting proper protein folding, while also being released from cells with EVs as well as a soluble form known as alarmins. We have here investigated the secretory phenotype of castration-resistant prostate cancer (CRPC) cells using proteome analysis. We have also examined the roles of the key co-chaperone CDC37 in the release of EV proteins including CD9 and epithelial-to-mesenchymal transition (EMT), a key event in tumor progression. EVs derived from CRPC cells promoted EMT in normal prostate epithelial cells. Some HSP family members and their potential receptor CD91/LRP1 were enriched at high levels in CRPC cell-derived EVs among over 700 other protein types found by mass spectrometry. The small EVs (30–200 nm in size) were released even in a non-heated condition from the prostate cancer cells, whereas the EMT-coupled release of EVs (200–500 nm) and damaged membrane vesicles with associated HSP90α was increased after heat shock stress (HSS). GAPDH and lactate dehydrogenase, a marker of membrane leakage/damage, were also found in conditioned media upon HSS. During this stress response, the intracellular chaperone CDC37 was transcriptionally induced by heat shock factor 1 (HSF1), which activated the CDC37 core promoter, containing an interspecies conserved heat shock element. In contrast, knockdown of CDC37 decreased EMT-coupled release of CD9-containing vesicles. Triple siRNA targeting CDC37, HSP90α, and HSP90β was required for efficient reduction of this chaperone trio and to reduce tumorigenicity of the CRPC cells in vivo. Taken together, we define “stressome” as cellular stress-induced all secretion products, including EVs (200–500 nm), membrane-damaged vesicles and remnants, and extracellular HSP90 and GAPDH. Our data also indicated that CDC37 is crucial for the release of vesicular proteins and tumor progression in prostate cancer.

Highlights

We hypothesized that cancer-derived extracellular vesicles (EVs) induced epithelial-to-mesenchymal transition (EMT) in normal epithelial cells
Vesicular CD9 was increased upon the heat shock stress (HSS), while intracellular levels decreased in the castration-resistant prostate cancer (CRPC) cells, suggesting that cellular CD9 was transmitted to EVs upon HSS. These findings indicate that HSP90α was released with EVs in response to proteotoxic stress, while non-vesicular HSP90α was released in response to the HSS
These results indicated that HSS induced the release of lactate dehydrogenase (LDH) from the CRPC cells potentially through membrane damage of the cells. small EVs (sEV) and heat shock protein 90 (HSP90) could be co-released with LDH upon the membrane damage caused by HSS

Summary

Introduction

Tumor cells are often exposed to various stresses such as immune/inflammatory stress, therapeutics [1], hypoxia [2,3,4], acidification, oxidative stress [5,6], starvation [7], nutrient stress [8], heat and cold [9,10], thermal stress, replication stress [11], endoplasmic reticulum (ER) stress, neurotoxic stress [12], genotoxic (DNA damage) [13] and proteotoxic stress [14,15]. Heat shock proteins (HSPs) were originally found to be induced upon heat shock stress (HSS) [9]. Later studies have revealed that other types of stresses can induce HSPs, including hypoxia [16] and nutrient starvation [7]. HSPs are molecular chaperones that assist in proper protein folding and re-folding in the cells, playing stress-resistant roles in anti-apoptotic activity [9] against radiation therapy, chemotherapy, and immunotherapy. It has been shown that HSPs are often increased in tumor cells and are involved in the properties of tumor progression such as increased migration, invasion, and metastasis [17,18]. Extracellular HSPs are released from cells with vesicles as well as a soluble form [4,19,20]

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Conclusion