Re-examining HSPC1 inhibitors

Exogenous heat shock proteins HSPA1A and HSPB1 regulate TNF-α, IL-1β and IL-10 secretion from monocytic cells

Endogenous molecules, such as heat shock proteins (HSP), can function as danger signals when released into the extracellular environment in response to cell stress, where they elicit an immune response such as cytokine secretion. There has also been some suggestion that contamination of exogenous HSPs with lipopolysaccharide (LPS) may be responsible for these effects. This study investigates the effects of exogenous HSPA1A and HSPB1 on the activation of immune cells and the resulting secretion of cytokines, which are involved in inflammatory responses. To address whether exogenous HSPs can directly activate cytokine secretion, naïve U937 cells, differentiated U937 cells and peripheral blood mononuclear cells (PBMCs) were treated with either exogenously applied HSPA1A or HSPB1 and then secreted IL-1β, TNF-α and IL-10 were measured by ELISA. Both HSPs were able to induce a dose-dependent increase in IL-10 secretion from naïve U937 cells and dose-dependent IL-1β, TNF-α and IL-10 secretion were also observed in differentiated U937 cells and PBMCs. We also observed that CD14 affects the secretion levels of IL-1β, TNF-α and IL-10 from cells in response to exogenous HSP treatment. In addition, HSPA1A and HSPB1 were shown to interact with CD14, CD36 and CD11b extracellular receptor proteins. Several approaches used in this study indicate that HSP-induced cytokine secretion is largely independent of any contaminating LPS in the samples.

TAS-116 (pimitespib), a heat shock protein 90 inhibitor, shows efficacy in preclinical models of adult T-cell leukemia

Adult T‐cell leukemia/lymphoma (ATL) is a highly chemoresistant malignancy of peripheral T lymphocytes caused by human T‐cell leukemia virus type 1 infection, for which there is an urgent need for more effective therapeutic options. The molecular chaperone heat shock protein 90 (HSP90) plays a crucial role in nuclear factor‐κB (NF‐κB)‐mediated antiapoptosis in ATL cells, and HSP90 inhibitors are new candidate therapeutics for ATL. Accordingly, we investigated the anti‐ATL effects of a novel oral HSP90 inhibitor, TAS‐116 (pimitespib), and the mechanisms involved in ex vivo and in vivo preclinical models. TAS‐116 achieved IC₅₀ values of less than 0.5 μmol/L in 10 ATL‐related cell lines and less than 1 μmol/L in primary peripheral blood cells of nine ATL patients; no toxicity was observed toward CD4⁺ lymphocytes from healthy donors, indicating the safety of this agent. Given orally, TAS‐116 also showed significant inhibitory effects against tumor cell growth in ATL cell‐xenografted mice. Furthermore, gene expression profiling of TAS‐116‐treated Tax‐positive or ‐negative cell lines and primary ATL cells using DNA microarray and multiple pathway analysis revealed the significant downregulation of the NF‐κB pathway in Tax‐positive cells and cell‐cycle arrest in Tax‐negative cells and primary ATL cells. TAS‐116 suppressed the activator protein‐1 and tumor necrosis factor pathways in all examined cells. These findings strongly indicate the efficacy of TAS‐116, regardless of the stage of ATL progression, and its potential application as a novel clinical anti‐ATL therapeutic agent.

Role of HSP27 in the multidrug sensitivity and resistance of colon cancer cells

Multidrug resistance in cancer cells is a primary factor affecting therapeutic efficacy. Heat shock 27 kD protein 1 (HSP27) is associated with cell apoptosis and resistance to chemotherapy. However, the mechanisms underlying HSP27-associated pathways in colon cancer cells remain unclear. Therefore, the present study used short hairpin (sh) RNA to inhibit HSP27 expression in colon cancer cells in order to investigate the effects in vitro and in vivo. Flow cytometry was used to investigate cell apoptosis and a xenograft model was employed to examine the tumorigenesis. Protein expression was measured by Western blotting. The results revealed that suppression of HSP27 expression significantly increased cell apoptosis, inhibited tumor growth and enhanced sensitivity to the anti-cancer agents 5-fluorouracil (5-FU) and vincristine (VCR). shHSP27 significantly decreased the expression of notch receptor 1 and the phosphorylation level of Akt and mTOR, and enhanced the effect of 5-FU and VCR. In conclusion, HSP27 suppression enhanced the sensitivity of colon cancer cells to 5-FU and VCR, and increased colon cancer cell apoptosis with and without chemotherapy. Therefore, the development of novel therapeutic agents that inhibit the expression of HSP27 may offer a new treatment option for colon cancer.