Fig. 4

Elevated expression of either ErbB2 or ErbB3 or direct activation of their downstream signaling attenuates VPA-induced inhibition of cell proliferation/survival as well as apoptosis in pancreatic cancer cells. a Exogenous expression of either ErbB2 or ErbB3 was introduced via lentiviral expression system in HPAF-II and MPanc96 cells. Cells with stable resistance to Puromycin were harvested and subjected to western blot analyses with specific antibodies directed against ErbB2, ErbB3, P-Akt, Akt, P-MAPK, MAPK, or β-actin. b HPAF-II and MPanc96 cells without or with elevated expression of either ErbB2 or ErbB3 were plated onto 96-well plates with complete culture medium (RPMI1640, 10% FBS). After 24 h, the medium was replaced with control medium (fresh RPMI1640, 0.5% FBS) or same medium containing indicated concentrations of VPA for another 72 h incubation. The percentages of surviving cells from each treatment to controls, defined as 100% survival, were determined by reduction of MTS. c, d HPAF-II and MPanc96 cells without or with elevated expression of either ErbB2 or ErbB3 were treated with VPA (1 mmol/L) for 24 h. Cells were harvested and subjected to western blot analyses with specific antibodies directed against PARP, C-Casp-3 or β-actin (c), or apoptotic ELISA (d). e HPAF-II and MPanc96 cells were plated onto 96-well plates with complete culture medium (RPMI1640, 10% FBS). After 24 h, the medium was replaced with control medium (fresh RPMI1640, 0.5% FBS) or same medium containing indicated concentrations of either VPA alone, indicated concentrations of VPA in combination with NRG-1 (25 ng/mL), or indicated concentrations of VPA in combination with EGF (50 ng/mL) for another 72 h incubation. The percentages of surviving cells from each treatment to controls, defined as 100% survival, were determined by reduction of MTS. f, g HPAF-II and MPanc96 cells untreated or treated with either VPA (0.5 mmol/L) or NRG-1 (25 ng/mL) alone, or combinations of VPA and NRG-1 for 24 h were collected and subjected to western blot analyses with specific antibodies directed against PARP, C-Casp-3 or β-actin (f) or apoptotic-ELISA (g). h, i HPAF-II and MPanc96 cells untreated or treated with either VPA (0.5 mmol/L) or EGF (50 ng/mL) alone, or combinations of VPA and EGF for 24 h were collected and subjected to western blot analyses with specific antibodies directed against PARP, C-Casp-3 or β-actin (h) or apoptotic-ELISA (i). Bars, S.D. Data show the representative of three independent experiments