The Role of Heat Shock Proteins in Cisplatin Resistance.

BACKGROUND: Cisplatin (CDDP), a small molecule platinum-based compound, is an effective anticancer drug used against a wide range of human neoplasms. Long-term clinical use of CDDP is however limited due to the development of drug resistance and the possible incidence of serious side effects including nephrotoxicity and ototoxicity. The mechanisms underlying resistance of cells to CDDP are complex, and among them, the cytoprotective involvement of proteins referred to as Heat Shock Proteins (HSP) seems potentially important. METHODS: We searched various electronic databases including PubMed and selected the reports concerning the contribution of HSPs to CDDP resistance of cancer cells and to minimize the CDDP-induced nephrotoxicity and ototoxicity. RESULTS: This critical review of data collected so far summarizes the results on the major HSPs: HSP27/HSPB1, HSP70/HSPA1, HSP90/HSPC and GRP78/HSPA5, because only these have been the subject of the most intense research in the matter discussed here. We also provide relevant information concerning some other HSPs, namely HSPA9/mortalin, HSPA2, HSP110 and DNAJ. A possible role of HSPs in counteracting CDDP-induced neprho- and ototoxicity is mentioned. CONCLUSIONS: This review shows that no universal relationship between the levels of expression of HSPs and sensitivity of cancer cells to CDDP can be confirmed. Multiple observations indicate however that such correlation can rather manifest as a molecular or cellular context-dependent phenomenon. Thus, HSPs can be viewed as an important component of the multifactorial, complex response of cancer cells to CDDP. However, to strengthen such a conviction, more extensive studies are needed.

Novel role for the testis-enriched HSPA2 protein in regulating epidermal keratinocyte differentiation.

HSPA2, a poorly characterized member of the HSPA (HSP70) chaperone family, is a testis-enriched protein involved in male germ cell differentiation. Previously, we revealed that HSPA2 is present in human stratified epithelia, including epidermis, however the contribution of this protein to epithelial biology remained unknown. Here, we show for the first time that HSPA2 is expressed in basal epidermal keratinocytes, albeit not in keratinocytes exhibiting features attributed to primitive undifferentiated progenitors, and participates in the keratinocyte differentiation process. We found that HSPA2 is dispensable for protection of HaCaT keratinocytes against heat shock-induced cytotoxicity. We also shown that lentiviral-mediated shRNA silencing of HSPA2 expression in HaCaT cells caused a set of phenotypic changes characteristic for keratinocytes committed to terminal differentiation such as reduced clonogenic potential, impaired adhesiveness and increased basal and confluency-induced expression of differentiation markers. Moreover, the fraction of undifferentiated cells that rapidly adhered to collagen IV was less numerous in HSPA2-deficient cells than in the control. In a 3D reconstructed human epidermis model, HSPA2 deficiency resulted in accelerated development of a filaggrin-positive layer. Collectively, our results clearly show a link between HSPA2 expression and maintenance of keratinocytes in an undifferentiated state in the basal layer of the epidermis. It seems that HSPA2 could retain keratinocytes from premature entry into the terminal differentiation process. Overall, HSPA2 appears to be necessary for controlling development of properly stratified epidermis and thus for maintenance of skin homeostasis.