Development of c-Kit-expressing Small-Cell Lung Cancer in a Chronic Myeloid Leukemia Patient During Imatinib Treatment

The achievement of durable complete cytogenetic remission in late chronic and accelerated phase patients with CML treated with Imatinib mesylate predicts for prolonged response at 6 years

Despite the positive results achieved by Imatinib mesylate (Imatinib) in the treatment of chronic myeloid leukemia (CML), over the past several years, Imatinib does not eradicate the leukemic clone. The long-term duration of response to the drug is not known. Long-term follow-up of CML patients treated with Imatinib will ultimately define the durability of such treatment and the frequency of reemergence of progressive disease. We present the results of a 6-year follow-up of 40 CML patients either in chronic or accelerated phase who obtained a durable (>6 months) complete cytogenetic remission (CCyR) after treatment with Imatinib in a single center. In 34 cases CCyR was obtained at an Imatinib dose of 400-600 mg/day and in 6 cases after a dose increase to 600-800 mg/day. At a median follow-up of 68 months, 6 cytogenetic relapses (15%) were observed. No progressions to more advanced phases of disease have been detected during the follow-up period. Cytogenetic relapse was predicted by either a decrease in the amount of BCR-ABL transcript of less than 2 logs after the achievement of CCyR (p=0.0041) or a time-to-CCyR of more than 12 months (p<0.0001). This 6-year follow-up of the efficacy of Imatinib therapy in CML patients who obtained a durable CCyR indicates that the relapses rate is low over this period of observation and that the rate of relapse does not increase over time.

Immunohistochemical and Mutational Analysis of c-kit in Gastrointestinal Neuroendocrine Cell Carcinoma

BACKGROUND

Gastrointestinal neuroendocrine cell carcinoma (NEC) is a highly aggressive tumor with poor prognosis, for which an effective therapy is highly desirable. Recently, use of a c-kit inhibitor achieved excellent results against gastrointestinal stromal tumor (GIST) that showed c-kit overexpression and mutation in most cases. According to recent studies, 17-44% of pulmonary NEC also expressed c-kit and the antitumor effect of c-kit inhibitor was demonstrated in vitro against small cell carcinoma of the lung. As gastrointestinal NECs are clinicopathologically similar to pulmonary NECs, we investigated c-kit expression and mutation in gastrointestinal NEC.

METHODS

Surgically resected gastrointestinal NEC was examined for c-kit expression by immunohistochemistry and RT-PCR. Mutation of the c-kit gene was also investigated by means of single-strand conformation polymorphisms (SSCP).

RESULTS

Twenty-six percent (6 out of 23 patients) of gastrointestinal NEC expressed c-kit protein. c-kit protein expression was demonstrated in 1 out of 4 colorectal, 1 out of 2 duodenal, 4 out of 16 gastric and no esophageal (sample size of 1) NECs. The results of immunohistochemistry for c-kit were consistent with the RT-PCR. No c-kit gene mutation was found in gastrointestinal NEC.

CONCLUSION

The frequency of c-kit expression in gastrointestinal NEC was similar to that previously reported for pulmonary NEC. These findings suggest that c-kit inhibitor may be effective against some gastrointestinal NECs.

Carcinogenesis, cancer therapy and chemoprevention

Carcinogenesis and cancer therapy are two sides of the same coin, such that the same cytotoxic agent can cause cancer and be used to treat cancer. This review links carcinogenesis, chemoprevention and cancer therapy in one process driven by cytotoxic agents (carcinoagents) that select either for or against cells with oncogenic alterations. By unifying therapy and cancer promotion and by distinguishing nononcogenic and oncogenic mechanisms of resistance, I discuss anticancer- and chemopreventive agent-induced carcinogenesis and tumor progression and, vice versa, carcinogens as anticancer drugs, anticancer drugs as chemopreventive agents and exploiting oncogene-addiction and drug resistance for chemoprevention and cancer therapy.