Abstract
Recently, a fusion protein of echinoderm microtubule associated protein like-4 (EML4) and anaplastic lymphoma kinase (ALK) has been found in non-small cell lung cancer (NSCLC) patients. In addition, endogenous expression of phosphorylated c-Met was found to be increased in many invasive NSCLC cases. PF-02341066 (crizotinib) is a novel dual c-Met and EML4-ALK inhibitor, and preclinical studies have shown that treatment with ALK inhibitors leads to drastic tumor regression in xenograft models. A phase I trial of PF-02341066 yielded a 53% response rate and a disease control rate of 79%. We evaluated crizotinib as a potential radiation-sensitizing agent in multiple established NSCLC cell lines with varying expression levels of c-Met and EML4-ALK. The combined effect of ionizing radiation (IR) and PF-02341066 was determined by the surviving cell fraction, cell cycle distribution, apoptosis, DNA double-strand break repair in 5 NSCLC cell lines (A549, H460, H3122, H2228 and H1993) and in in vivo xenograft studies. Treatment of NSCLC cells with either PF-02341066 alone or PF-02341066 + IR did not significantly alter cellular radiosensitivity, DNA repair kinetics and cell cycle distribution; no significant enhancement of tumor growth delay was noted in response to the combined treatment of PF-02341066 + IR. EML4-ALK and c-Met inhibition leads to activation of parallel pathways that converge on Akt signaling which abrogates any radiation-sensitizing effect. Although PF-02341066 is an effective therapy able to suppress tumor growth in tumors that exhibit positivity for either EML4-ALK or c-Met, it did not affect the intrinsic radiation response of tumor cell lines. In the present study, we demonstrated that PF-02341066 did not enhance radiation sensitivity in a panel of NSCLC cell lines.