Abstract 2792: Targeting heme and oxidative phosphorylation suppresses lung tumor growth and normalizes tumor vascular oxygenation
Authors: Ghosh Poorva , Ashrafi Adnin , Dey Sanchareeka , Liu Li , Zhang Li 
Published: September 2020

Lung cancer is the leading cause of cancer-related death in the US of which 85-90% of cases are classified as non-small cell lung cancer (NSCLC). Despite the advent of targeted therapies and immunotherapies, effective therapies for lung cancer are elusive for most patients. Thus, alternative approaches are required for treatment of lung cancer. Recent studies in our lab show that NSCLC cells demonstrate elevated levels of heme via increased heme uptake and synthesis, as well as elevated mitochondrial respiration/oxidative phosphorylation (OXPHOS) which fuels NSCLC growth and progression. Also, limiting heme via inhibition of heme synthesis with Cyclopamine tartrate (CycT) or inhibition of heme uptake with heme sequestering peptides (HSP2) delays the growth and progression of NSCLC tumors. The tumor microenvironment (TME) influences tumor heterogeneity, invasion, and metastasis and is a major contributor to cancer progression.

Tumor vasculature and oxygenation are important aspects of TME; however, faulty tumor vascular oxygenation is a marker for poor prognosis in cancer. Given the central role of heme in oxygen transport, utilization, and storage, it is important to investigate the effect of limiting heme on tumor vascular oxygenation.

To gain insights into mechanism by which the heme targeting drugs (CycT and HSP2) limit tumor growth and progression, we implanted subcutaneous/orthotopic lung tumor xenografts of luciferase expressing NSCLC cell lines in NOD-SCID mice. Mice were treated with saline (control) or CycT or HSP2. Tumor growth was monitored using bioluminescence imaging (BLI). Mice were subjected to multispectral optoacoustic tomography (MSOT) to visualize tumor vasculature, oxygenation and hypoxia. MSOT data was acquired at multiple wavelengths to calculate total hemoglobin concentrations (THb) and oxygenation (sO2). Tumors were resected on sacrifice and homogenized to perform oxygen consumption and ATP assays. Tumors/lung tissues were harvested, processed and paraffin embedded for immunohistochemistry (IHC) and histology experiments.

BLI data, tumor volumes, masses, and hematoxylin and eosin (H&E) show that CycT or HSP2 treatment suppresses growth of subcutaneous/lung orthotopic tumor xenografts. CycT and HSP2 treated tumors also show reduced oxygen consumption and ATP levels compared to control. MSOT data show that THb levels were decreased by CycT or HSP2 treatment. OE-MSOT (Oxygen enhanced MSOT) data show increased levels of sO2MSOT in HSP2- or CycT-treated tumors compared to control tumors. IHC data for various hypoxia and angiogenesis markers confirm that limiting heme effectively normalizes tumor vascular oxygenation.

Thus, heme-targeting drugs are promising candidates to effectively inhibit angiogenesis, normalize tumor vasculature, and alleviate tumor hypoxia in NSCLC tumors thereby delaying lung tumor growth and progression.

Citation Format: Poorva Ghosh, Adnin Ashrafi, Sanchareeka Dey, Li Liu, Li Zhang. Targeting heme and oxidative phosphorylation suppresses lung tumor growth and normalizes tumor vascular oxygenation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2792.