Elevated Heme Synthesis and Uptake Underpin Intensified Oxidative Metabolism and Tumorigenic Functions in Non–Small Cell Lung Cancer Cells

Abstract

HSP2HSP2 HEME HCP1 HRG1 HEME HEME HEME CYT NUC ER ALA SLung cancer cells exhibit elevated heme synthesis and uptake, which promotes tumorigenic functions. Heme-sequestering peptide 2 (HSP2) inhibits heme uptake and suppresses tumor growth. V [ ] Lung tumors Non-small cell lung cancer cell Normal lung I II III IV ATP ADPTumors of human non-small cell lung cancer (NSCLC) are heterogeneous but exhibit elevated glycolysis and glucose oxidation relative to benign lung tissues. Heme is a central molecule for oxidative metabolism and ATP generation via mitochondrial oxidative phosphorylation (OXPHOS). Here, we showed that levels of heme synthesis and uptake, mitochondrial heme, oxygen-utilizing hemoproteins, oxygen consumption, ATP generation, and key mitochondrial biogenesis regulators were enhanced in NSCLC cells relative to nontumorigenic cells. Likewise, proteins and enzymes relating to heme and mitochondrial functions were upregulated in human NSCLC tissues relative to normal tissues. Engineered heme-sequestering peptides (HSP) reduced heme uptake, intracellular heme levels, and tumorigenic functions of NSCLC cells. Addition of heme largely reversed the effect of HSPs on tumorigenic functions. Furthermore, HSP2 significantly suppressed the growth of human NSCLC xenograft tumors in mice. HSP2-treated tumors exhibited reduced oxygen consumption rates (OCR) and ATP levels. To further verify the importance of heme in promoting tumorigenicity, we generated NSCLC cell lines with increased heme synthesis or uptake by overexpressing either the ratelimiting heme synthesis enzyme ALAS1 or uptake protein SLC48A1, respectively. These cells exhibited enhanced migration and invasion and accelerated tumor growth in mice. Notably, tumors formed by cells with increased heme synthesis or uptake also displayed elevated OCRs and ATP levels. These data show that elevated heme flux and function underlie enhanced OXPHOS and tumorigenicity of NSCLC cells. Targeting heme flux and function offers a potential strategy for developing therapies for lung cancer. IntroductionLung cancer is the leading cause of cancer-related deaths in the United States (1). About 85% of cases are non-small cell lung cancer (NSCLC). Although several chemotherapeutic and targeted therapeutic agents are approved for treating lung cancer, the 5-year survival rate remains 18%. The effectiveness of targeted therapies for lung cancer is lowered by the presence of multiple driver genes and intratumoral genetic heterogeneity (2). Likewise, three PD-1/PD-L1 checkpoint inhibitors, nivolumab, pembrolizumab, and atezolizumab, generally extend median overall survival by about 3 months for second-line treatment of advanced NSCLC, compared with docetaxel alone (3-5). In the front-line setting, the median progression-free survival extends from 6.0 months with platinum-doublet chemotherapy to 10.3 months with pembrolizumab in patients with untreated NSCLC characterized by a high level of PD-L1 expression (6). Thus, alternative therapeutic strategies are still needed for lung canc...

Heme synthesis inhibition blocks angiogenesis via mitochondrial dysfunction

“…Apart from ECs, nonsmall cell lung carcinoma cells with elevated heme synthesis levels had increases in enzyme activities of the ETC. Increased production of heme was associated with increased migratory and invasive properties of these cells and xenograft tumors in mice (Sohoni et al, 2019). Here, we demonstrated how heme depletion by blockade of the terminal synthesis enzyme FECH led to defects in COX IV and ETC disruption ( Figure 7).…”

Targeting the Mitochondrial Metabolic Network: A Promising Strategy in Cancer Treatment

“…Moreover, a study performed in human patients in order to analyze metabolic pathways’ flow in non-small-cell lung cancer (NSCLC) displayed that high rates of both glycolysis and oxidative metabolism can be observed in this cancer type, highlighting a metabolic heterogeneity strongly influenced by microenvironment. In addition, Sohoni et al highlighted that the elevated OXPHOS activity and tumorigenicity characterizing NSCLC cells are related to elevated both flux and function of heme, a key molecule in mitochondrial OXPHOS [ 26 ].…”

“…Several studies have correlated a high heme dietary intake through the consumption of red and processed meat with the pathogenesis of different carcinomas, such as esophageal, gastric, colorectal, breast, endometrial, pancreatic, and lung cancer. In addition, increased heme biosynthesis and uptake have been found in several tumors, including non-small-cell lung cancer, in which high heme levels, as well as an increased activity of heme proteins, have been shown to underlie metabolic rewiring and tumor progression [ 26 , 78 , 79 ]. This evidence highlights the important role in cancer of heme uptake, as well as of its biosynthesis and incorporation into oxygen-utilizing heme proteins, and has led to the study of molecules targeting these processes as a new anticancer strategy [ 80 ] ( Figure 3 ).…”

“…Furthermore, a different strategy recently adopted is represented by the use of heme-sequestering peptides. By making appropriate modifications to the amino acid sequence of Yersinia pestis hemophore HasA, new heme-sequestering peptides, namely HSP1 and HSP2, have been developed and shown to reduce proliferation, migration, and invasion of non-small-cell lung cancer cells both in vitro and in vivo [ 26 ].…”

Heme, A Metabolic Sensor, Directly Regulates the Activity of the KDM4 Histone Demethylase Family and Their Interactions with Partner Proteins

“…Heme directly binds to and modulates the activities of certain cellular proteins, such as the yeast heme-regulatory protein Hap1 [51,52] and the mammalian nuclear receptor Rev-erbα [49,53]. Experimental studies have increasingly shown that heme is a central signaling molecule in an array of physiological and pathological processes, including neurodegeneration, tumorigenesis, and adipogenesis [54][55][56].…”