Abstract 1108: Evaluation of heme inhibitory therapy in combination with chemotherapy drugs on SCLC progression

Abstract Lung cancer is the leading cause of cancer-related death in the US. It is mainly divided in two types: small cell lung cancer and non-small cell lung cancer. About 85-90% of cases are classified as non-small cell lung cancer (NSCLC). Small cell lung cancer (SCLC) is an aggressive neuroendocrine lung tumor representing 15% of lung cancers. Despite the advent of targeted therapies and chemotherapies, effective therapies for lung cancer are an unlikely outcome for most patients. SCLC is initially highly responsive to cisplatin and etoposide chemotherapy but, in almost every case, becomes rapidly chemo resistant. However, the mechanisms underlying initial sensitivity and subsequent resistance are not well investigated. Thus, alternative approaches and combination therapy is required for treating SCLCs. Recent studies in our lab show that NSCLC cells demonstrate elevated levels of heme via increased heme uptake and synthesis, and elevated oxidative phosphorylation (OXPHOS) and ATP generation which fuels NSCLC proliferation. Also, limiting heme via inhibition of heme uptake using heme sequestering peptides (HeSP2) can delay growth and progression of NSCLC tumors. This HeSP2 can also effectively inhibit angiogenesis, normalize tumor vasculature, and alleviate tumor hypoxia in NSCLC tumors and thereby inhibit lung tumor growth and progression. Tumor heterogeneity is critical for tumor growth, metastasis, and acquired therapeutic resistance. To understand if heme can effectively reduce tumor cell proliferation and growth and improve tumor microenvironment, we treated chemo resistant SCLCs with HeSP2 and in combination with commonly used chemo drugs cisplatin and etoposide. Our data shows that HesP2 can strongly inhibit cell proliferation and decreases oxygen consumption rate along with ATP generation in SCLCs. To gain insights into mechanism by which the heme sequestering peptides limit tumor growth and progression, we implanted subcutaneous or SCLC cell lines in NOD/SCID mice. Mice were treated with saline (control), HeSP2, HeSP2 and cisplatin, HeSP2 and etoposide. Tumor growth was monitored using caliper measurements. Tumors tissues were harvested, processed and paraffin embedded for immunohistochemistry (IHC) and histology experiments. These results indicate that heme sequestration can be a powerful strategy for suppressing lung tumors likely drug-resistant tumors that rely on oxidative phosphorylation for survival. Citation Format: Adnin Ashrafi, Narges Salamat, Li Zhang. Evaluation of heme inhibitory therapy in combination with chemotherapy drugs on SCLC progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1108.