Autophagy-associated proteins BAG3 and p62 in testicular cancer

Abstract

Abstract. Testicular germ cell tumors (TGCT) represent the most common malignant tumor group in the age group of 20 to 40-years old men. The potentially curable effect of cytotoxic therapy in TGCT is mediated mainly by the induction of apoptosis. Autophagy has been discussed as an alternative mechanism of cell death but also of treatment resistance in various types of tumors. However, in TGCT the expression and role of core autophagy-associated factors is hitherto unknown. We designed the study in order to evaluate the potential role of autophagy-associated factors in the development and progression of testicular cancers. Eighty-four patients were assessed for autophagy (BAG3, p62) and apoptosis (cleaved caspase 3) markers using immunohistochemistry (IHC) on tissue microarrays. In addition, western blot analyses of frozen tissue of seminoma and non-seminoma were performed. Our findings show that BAG3 was significantly upregulated in seminoma as compared to non-seminoma but not to normal testicular tissue. No significant difference of p62 expression was detected between neoplastic and normal tissue or between seminoma and non-seminoma. BAG3 and p62 showed distinct loco-regional expression patterns in normal and neoplastic human testicular tissues. In contrast to the autophagic markers, apoptosis rate was significantly higher in testicular tumors as compared to normal testicular tissue, but not between different TGCT subtypes. The present study, for the first time, examined the expression of central autophagy proteins BAG3 and p62 in testicular cancer. Our findings imply that in general apoptosis but not autophagy induction differs between normal and neoplastic testis tissue. IntroductionThe effect of cytotoxic treatment in testicular tumors is mainly moderated by the induction of apoptosis (1). Due to the rapid response after exposure to chemotherapeutic agents an intact and effective apoptotic pathway in most testicular cancers is assumed (2). Nevertheless, various patients show complex clinical courses, including tumors with chemoresistence and thus lower apoptosis rates (3). Recent studies have shown that the elimination of cells may be also conducted using the alternative cell death pathway ʻautophagyʼ (4,5).Autophagy is an evolutionarily conserved, pervasive and multi-step ʻself-eatingʼ process, by which cytosolic material is sequestered in a double-lipid membrane, delivered to the lysosome for degradation and digested to provide energy and to build the foundation for cell-survival (6). While autophagy has for long been considered to be a bulk degradation process, recent discoveries show that it rather displays a sophisticated portfolio of selectivity provided by different molecular strategies such as the detection of several autophagy receptor proteins, including pacemaker molecules such as p62 (SQSTM1) and BCL2-associated athanogene 3 (BAG3) (7-9). To the best of our knowledge, no study has been published to date that examined the expression of the cohesive autophagy proteins BAG3 and p62 in testicular can...

Downregulation of Autophagy-Related Proteins 1, 5, and 16 in Testicular Germ Cell Tumors Parallels Lowered LC3B and Elevated p62 Levels, Suggesting Reduced Basal Autophagy

“…For a retrospective study of autophagy, differences in patients' cohorts and experimental procedures, especially the source of the antibodies, may also lead to different conclusions. For example, in another study, no significant difference in autophagy was found between non-neoplastic and TGCT patients using a p62 antibody different from ours ( 17 ). Nevertheless, our evaluation of the expression of ATGs as well as LC3B and p62 strongly suggests a reduction in autophagy in TGCT and points to a possible inhibitory function of the autophagic pathway in the tumorigenesis of TGCT.…”

Role of 5‑Aza‑CdR in mitomycin‑C chemosensitivity of T24 bladder cancer cells

“…It was demonstrated that the expression levels of beclin 1, p62 and ATG5 protein in T24 cells were decreased in a dose-dependent manner following treatment with MMC and increasing 5-Aza-CdR concentrations. Beclin 1, p62 and ATG5 are considered as the key regulators of autophagic cell death (14)(15)(16). Autophagy is a lysosome-dependent self-digesting system primarily responsible for the removal and recycling of long-lived proteins, and damaged or obsolete intracellular organelles, in order to maintain cell homeostasis (17).…”

At the Crossroads of Apoptosis and Autophagy: Multiple Roles of the Co-Chaperone BAG3 in Stress and Therapy Resistance of Cancer

“…No difference between normal and tumor tissue, but higher BAG3 expression in seminoma compared to non-seminoma tumors; higher BAG3 and p62 expression in perivascular areas and in proximity to necrotic foci [71] Thyroid Cancer Little to no expression in normal tissue; high expression in most tumor samples [44]…”