pd-184161 and Liver-Neoplasms

Hepatocellular cancer (HCC) is a leading cause of cancer-related death worldwide. Historically, doxorubicin (DOX) has been widely used against unresectable HCC with variable response rates.. We hypothesized that DOX combined with mitogen-activated protein kinase kinase-extracellular signal-regulated kinase (MEK-ERK) targeted therapy may provide enhanced anti-cancer effects. Human HCC cell lines (HepG2, Hep3B) were treated with DOX and MEK enzyme inhibitors, U0126 or PD184161, alone or in combination. Growth, apoptosis, and ERK expression/MEK activity were respectively determined by proliferation assay, DNA fragmentation enzyme-linked immunoassay or fluorochrome inhibitor of caspases, and Western blot.. DOX (0.01-1 microM) decreased cell proliferation in Hep3B cells (IC(50) approximately 0.12 microM) at 48 to 72 h; DOX was less effective in HepG2 cells (IC(50) approximately 0.25 microM). At early time points (30 min) after DOX treatment of Hep3B cells, MEK activity was unchanged at low doses and decreased at higher doses; after 24 h, phospho-ERK levels increased at higher doses. Contrarily, in HepG2 cells, DOX caused a sustained, dose-dependent increase in phospho-ERK levels at early and late time points. The MEK inhibitor U0126 decreased phospho-ERK in both HCC lines. In contrast to DOX, HepG2 cells were more sensitive than Hep3B cells to U0126. The combination of DOX with U0126 (or PD184161) resulted in greater inhibition of proliferation in HepG2 but not in Hep3B cells. This effect may be mediated in part by enhanced apoptosis.. The effect of DOX on early and late induction of MEK activity predicts its chemotherapeutic response in HCC. Furthermore, this effect may also determine the utility of MEK inhibitor combination treatment.

Topics: Aniline Compounds; Antibiotics, Antineoplastic; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzamides; Butadienes; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Doxorubicin; Enzyme Inhibitors; Humans; Liver Neoplasms; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase Kinases; Nitriles; Phosphorylation

The MEK-ERK growth signaling pathway is important in human hepatocellular carcinoma (HCC). To evaluate the targeting of this pathway in HCC, we characterized a novel, orally-active MEK inhibitor, PD184161, using human HCC cells (HepG2, Hep3B, PLC, and SKHep) and in vivo human tumor xenografts. PD184161 inhibited MEK activity (IC50 = 10-100 nM) in a time- and concentration-dependent manner more effectively than PD098059 or U0126. PD184161 inhibited cell proliferation and induced apoptosis at concentrations of > or = 1.0 microM in a time- and concentration-dependent manner. In vivo, tumor xenograft P-ERK levels were significantly reduced 3 to 12 hours after an oral dose of PD184161 (P < .05). Contrarily, tumor xenograft P-ERK levels following long-term (24 days) daily dosing of PD184161 were refractory to this signaling effect. PD184161 significantly suppressed tumor engraftment and initial growth (P < .0001); however, established tumors were not significantly affected. In conclusion, PD184161 has antitumor effects in HCC in vitro and in vivo that appear to correlate with suppression of MEK activity. These studies demonstrate that PD184161 is unable to suppress MEK activity in HCC xenografts in the long term. Thus, we speculate that the degree of success of MEK targeted treatment in HCC and other cancers may, in part, depend on the discovery of mechanisms governing MEK inhibitor signaling resistance.

Topics: Aniline Compounds; Animals; Antineoplastic Agents; Benzamides; Butadienes; Cell Line, Tumor; Cell Proliferation; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Humans; Liver Neoplasms; MAP Kinase Kinase Kinases; Mice; Mice, Nude; Neoplasm Transplantation; Nitriles