O-158 A randomized phase II ECOG trial of two dose levels of temsirolimus (CCI-779) in patients with extensive stage small cell lung cancer in remission after induction therapy

Selective inhibition of SCLC growth by the A12 anti-IGF-1R monoclonal antibody correlates with inhibition of Akt

Activation of the insulin-like growth factor-1 receptor (IGF-1R) by IGF-1 and IGF-2 plays a prominent role in the growth and survival of small cell lung cancer (SCLC) by potently activating the PI3K-Akt signal transduction pathway, which is also an important factor in the resistance of SCLC to chemotherapy. A12 is a fully human monoclonal antibody directed against the human IGF-1R that does not cross-react with the insulin receptor. In this study we have utilized A12 to determine the effects of selective antibody-mediated blockade of the IGF-1R on SCLC cell lines. Incubation with A12 resulted in a dose-dependent inhibition of IGF-1-stimulated IGF-1R and Akt activity, with maximal inhibition of approximately 75% at a concentration of 10mug/ml in the H526 cell line. Growth of the H526 and H146 cell lines in serum was inhibited by a maximum of 50-70% in a dose-dependent fashion, which correlated well with the extent of Akt inhibition. However, growth of the H69 and WBA cell lines was unaffected by A12. Despite almost complete inhibition of IGF-1R phosphorylation by A12, Akt activity remained constitutively high in these cell lines. H526 transfectants expressing a constitutively active Akt allele also were resistant to A12. Treatment with A12 additively enhanced response to carboplatin in the H526 and H146 cell lines but had no effect on the H69 and WBA cell lines. Treatment of the H526 cell line with a combination of A12 and rapamycin was highly synergistic. These data suggest that growth inhibition and chemosensitization of SCLC by A12 is directly correlated with the ability to inhibit PI3K-Akt signaling, with those cell lines showing constitutive PI3K-Akt signaling displaying a high level of resistance to IGF-1R targeted therapy.

Management of small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive type of lung cancer characterized by rapid growth and early metastasis. It is chemosensitive and radiosensitive, yet decades of research investigating multimodality treatments have failed to control or cure this disease in most patients. First-line treatment of limited-stage disease consists of chemotherapy (often etoposide/cisplatin or etoposide/carboplatin) combined with thoracic radiation therapy (TRT), followed by prophylactic cranial irradiation to decrease brain metastases as a site of disease progression for those who experience complete remission or a very good partial response to multimodality treatment. In a Japanese trial, the combination of irinotecan and cisplatin had initially shown promise in treating patients with extensive-stage SCLC, but a confirmatory trial in the United States did not find a difference in overall survival with irinotecan/cisplatin versus etoposide/cisplatin. Adding a third drug to the etoposide/cisplatin combination, as well as other triplet therapies, has mostly been ineffective in improving outcomes. Variables in chemotherapy administration, including maintenance therapy, alternating non-cross-resistance regimens, and dose intensification, have not been shown to increase survival at large. In terms of radiation therapy, early administration of TRT concurrent with chemotherapy, and hyperfractionation, have been beneficial in treatment of limited-stage disease. In patients who relapse, second-line therapy options consist of reinduction of previous chemotherapy or administration of a single agent. Targeted biological therapies for SCLC are now being investigated, and although a great deal of research remains to be done, these agents and their derivatives may provide the most hope for future treatment of SCLC.