The present invention is directed to the use of benzimidazole derivatives for the treatment of tumors and in combination with tumor suppressor gene therapy. In a particular embodiment, treatment of p53-positive tumors with benzimidazole derivatives induces p53 expression and increases its half-life, resulting in apoptotic death of the tumor cells. Similarly, in conjunction with p53 gene therapy, benzimidazole derivatives induce p53 expression and accumulation in tumor cells regardless of their p53 status. The combination treatment subsequently elicits apoptosis of the tumor cells.