More importantly, either using specific ERK inhibitor PD98059 to pre-treat cells or using siRNA to knock down ERK protein expression significantly sensitized sub-lethal ABT-263-induced apoptosis in HCC cells, suggesting that ERK anti-apoptotic signal pathway activation could render cells resistant to this Bcl-2 inhibitor toxicity. The gene discussed is BCL2; the disease is hepatocellular carcinoma.