Purpose: Inhibitors of antiapoptosis protein (IAP) have been implicated in the resistance to cisplatin. Therefore, verifying which pathway is involved in cIAP2 upregulation may be helpful in finding a feasible pathway inhibitor to increase the chemotherapeutic efficacy in human papillomavirus (HPV)–infected lung cancer.

Experimental Design: Specific inhibitors of different pathways were used to verify which pathway is involved in cIAP2 transcription. cIAP2 promoter fragments with various deletions and/or mutations were constructed by site-directed mutagenesis. cIAP2, epidermal growth factor receptor (EGFR), and phospho-AKT (p-AKT) expressions in 136 lung tumors were evaluated by immunohistochemistry.

Results: Our data show that two NF-κB (−209 to −200 and −146 to −137) and one CREB (cyclic AMP–responsive element binding protein; −52 to −42) binding sites in cIAP2 promoter region were responsible for cIAP2 upregulated by E6 in TL-1 cells. Moreover, CREB was phosphorylated by EGFR/phosphatidylinositol 3-kinase (PI3K) pathway. To test the involvement of cIAP2 on cisplatin resistance, IC₅₀ was lowered to 8.6 μmol/L in TL-1 cells with cIAP2 short hairpin RNA (shRNA) transfection and compared with 39.7 μmol/L in TL-1 cells with nonspecific shRNA. Pretreatment with EGFR or PI3K inhibitor in TL-1 cells diminished the resistance to cisplatin. Among the tumor groups, cIAP2 expression correlated significantly with HPV16/18 E6, EGFR, and p-AKT. We followed up 46 of 136 patients who had tumor recurrence and/or metastasis and underwent chemotherapy. Tumors with cIAP2-positive immunostaining were associated with a poorer tumor response to chemotherapy compared with those with negative immunostaining.

Conclusions: cIAP2 upregulated by E6 via EGFR/PI3K/AKT cascades may contribute to cisplatin resistance, revealing that the EGFR or PI3K inhibitor combined with cisplatin may improve the chemotherapeutic efficacy in HPV-infected lung cancer. Clin Cancer Res; 16(21); 5200–10. ©2010 AACR.