Functional redundancy of HSPA1, HSPA2 and other HSPA proteins in non-small cell lung carcinoma (NSCLC); an implication for NSCLC treatment

Abstract

Heat shock proteins (HSPs) are a large group of chaperones considered critical for maintaining cellular proteostasis. Their aberrant expression in tumors can modulate the course of processes defined as hallmarks of cancer. Previously, we showed that both stress-inducible HSPA1 and testis-enriched HSPA2, highly homologous members of the HSPA (HSP70) family, are often overexpressed in non-small cell lung carcinoma (NSCLC). HSPA1 is among the best characterized cancer-related chaperones, while the significance of HSPA2 for cancer remains poorly understood. Previously we found that in primary NSCLC, HSPA1 was associated with good prognosis while HSPA2 correlated with bad prognosis, suggesting possible different roles of these proteins in cancer. Therefore, in this work we investigated the impact of HSPA1 and HSPA2 on NSCLC cell phenotype. We found that neither paralog-selective nor simultaneous knockdown of HSPA1 and HSPA2 gene expression reduced growth and chemoresistance of NSCLC cells. Only blocking of HSPA proteins using pan-HSPA inhibitors, VER-155008 or JG-98, exerted potent anticancer effect on NSCLC cells, albeit the final outcome was cell type-dependent. Pan-HSPA inhibition sensitized NSCLC cells to bortezomib, but not to platinum derivates. Our result suggests the inhibitors of proteasome and HSPAs seem an effective drug combination for pre-clinical development in highly aggressive NSCLC.

HSPA2 Chaperone Contributes to the Maintenance of Epithelial Phenotype of Human Bronchial Epithelial Cells but Has Non-Essential Role in Supporting Malignant Features of Non-Small Cell Lung Carcinoma, MCF7, and HeLa Cancer Cells

“…We found that a high reduction of HSPA2 levels in modified cells had no impact on proliferation ( Figure S2b ) and colony-forming ability ( Figure S2c ). Altogether, these results were in line with our earlier observations that shRNA-mediated knockdown of HSPA2 expression did not affect the proliferation, metabolic activity, and clone-forming ability of two cell lines originating from NSCLC, namely NCI-H23 (adenocarcinoma, arising from bronchial mucosal gland) and NCI-H1299 (derived from the metastatic tumor) [ 18 ].…”

“…In order to exclude the possibility that even a small amount of HSPA2 remaining after gene knockdown may be sufficient to support cell growth, we used the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9) gene editing method. We generated HSPA2 knockout in the NCI-H1299 cell line, which we had used previously in HSPA2 knockdown study [ 18 ]. We established a knockout pool: a mixed population of edited CRISPR-A2 cells that contained around a 90% decreased level of HSPA2 ( Figure 1 b), as well as a control CRISPR-ctr pool.…”

“…HSPA1 may also play a pivotal role in cancer development [ 15 ]. On the contrary, other reports show that only the simultaneous inhibition of several HSPA paralogs (including HSPA8), but not a paralog-selective reduction in the level of any of them, had anti-proliferative or cytotoxic effects in cancer cells [ 16 , 17 , 18 ].…”

“…Conversely, using siRNA-mediated gene silencing, it was shown that neither HSPA2 nor HSPA1 were essential to cancer cells’ viability [ 17 ]. In our recent study, we demonstrated that the growth and proliferation of two NSCLC cell lines remained unaltered after the stable shRNA-mediated single knockdown of HSPA2 or HSPA1A/B , as well as double HSPA2 / HSPA1A/B knockdown [ 18 ].…”

Functional diversity between HSP70 paralogs caused by variable interactions with specific co-chaperones

“…Due to their high conservation both in evolution and within the Hsp70 family, (human) Hsp70 proteins are often regarded as largely interchangeable (12)(13)(14)(15)(16)(17). However, specificity between Hsp70 machines does exist and different effects of the various Hsp70s have been reported (6,8,(18)(19)(20).…”