Heat shock proteins (HSPs) can regulate cell migration and proliferation and are known to be overexpressed in human pancreatic cancer (PC) tissue. The stromal reaction of PC is produced by activated pancreatic stellate cells (PSCs) which interact with PC cells to facilitate cancer progression and metastasis. Growth factors (including PDGF) produced by tumour cells induce proliferation and migration of PSCs. We have also previously shown that PDGF induces the expression of several HSPs (27, 47, 70 and 90) in human cancer associated-PSCs (CA-hPSC). However, little is known about the role of HSPs in PSC function. Aim: To determine the effect of silencing HSPs (27, 47, 70 or 90) in CA-hPSCs on cell migration and proliferation.
Methods: CA-hPSC were isolated from resected pancreatic tissue from PC patients and treated (n=4) with siRNA targeting HSP27 (protein 1 or 2), HSP47, HSP70, HSP90 (>90% protein silencing achieved) or non-silencing siRNA (ns-siRNA). 48h post transfection CA-hPSCs were incubated ± PDGF (10ng/ml) for 48h. Cell proliferation assessed by the cell counting kit-8 and migration assessed using modified Boyden chambers with PDGF as a chemotactic agent.
Results: PDGF stimulated CA-hPSC proliferation and migration in ns-siRNA treated PSCs (#p<0.001). Notably, silencing HSP27 (p1 and p2) or HSP47 inhibited PDGF-induced proliferation by 55.4±18.5%, 50.4±7.7%, and 72.8±14% (*p<0.01 vs ns-siRNA+PDGF) respectively. In contrast, HSP70 and HSP90 siRNA had no effect on PDGF-induced proliferation. However, silencing HSP27 (p1 and p2) and HSP47 had no effect on basal or PDGF-induced PSC migration.
Conclusion: This is the first study to show that suppression of HSP27 or HSP47 inhibits PDGF-induced PSC proliferation.
Implication: Modulation of HSPs in PSCs may represent a novel approach to influence PSC function and PSC interactions with pancreatic cancer cells.