Abstract 2681: Combination therapy of heme inhibitory protein (HeSP2) and Cyclopamine tartrate (CycT) with chemotherapeutic drugs is an effective strategy for treatment of TNBC

Breast cancer (BC) is the second leading cause of cancer death in women. Among the four main types of BC, triple-negative breast cancer (TNBC) accounts for 10 to 15% of BC. Although most TNBC patients have a poor prognosis, there are subsets of patients with tumors that respond well to chemotherapy. However, the outcome of chemotherapy in TNBC worsens over time due to the high expression of the oxidative phosphorylation (OXPHOS) complex. Likewise, drug resistant TNBC cells depend on OXPHOS; targeting oxidative metabolism and mitochondrial respiration can potentially overcome their drug resistance. Our lab recently engineered a heme-sequestering protein 2 (HeSP2) based on HasA hemophore. HeSP2 can effectively inhibit heme uptake and decrease the OXPHOS levels in cancer cells due to its high affinity for heme. Another agent, cyclopamine tartrate (CycT), previously known as a modulator of hedgehog signaling and mitochondrial respiration, can inhibit heme synthesis and reduce the OXPHOS levels. Therefore, using these heme-targeting agents in combination with chemotherapy could be an effective strategy to increase the therapeutic efficacy in TNBC. Cisplatin and etoposide are two chemotherapeutic drugs that have recently been used for treating TNBC. For this purpose, we examine the combination therapy of our OXPHOS inhibitory agents, HeSP2 and CycT, with cisplatin and etoposide in TNBC. In vitro experiment using three different TNBC cell lines, 4T1-Fluc-Neo, EMT6_Fluc_Puro, and MDA-MBA-231 confirmed the inhibitory effect of both HeSP2 and CycT in cell proliferation and colony formation in combination with or without chemo drugs. Results indicate that combination therapy significantly reduced the proliferation and inhibited colony formation in TNBC cells. As HeSP2 and CycT are therapeutic agents that reduce hypoxia and OXPHOS, they may also delay the emergence of drug resistance in cancer cells treated with chemotherapy. Our results indicate that HeSP2 and CycT in combination with chemotherapy drugs could serve as a promising therapy to diminish the tumorigenic function in TNBC and overcome resistance to chemotherapy. Citation Format: Parinaz Sadat Alemi, Maria del Carmen Chacon Castro, Eranda Berisha, Zakia Akter, Li Zhang. Combination therapy of heme inhibitory protein (HeSP2) and Cyclopamine tartrate (CycT) with chemotherapeutic drugs is an effective strategy for treatment of TNBC [abstract]. In: Proceedings of the American Association for Cancer Research Annu