journal contribution
posted on 2023-03-31, 01:47 authored by Sagar Sohoni, Poorva Ghosh, Tianyuan Wang, Sarada Preeta Kalainayakan, Chantal Vidal, Sanchareeka Dey, Purna Chaitanya Konduri, Li Zhang <p>Fig. S4. Proteins and enzymes relating to heme and mitochondrial functions are upregulated in human NSCLC tissues relative to control normal tissues. The examined proteins and enzymes include the rate-limiting heme synthetic enzyme ALAS1 (A), the heme transporter SLC48A1 (B), the hemoprotein OXPHOS subunit cytochrome c (CYCS) (C), hemoprotein PTGS2 (D), and the regulator promoting mitochondrial biogenesis TFAM (E). Shown are the representative Montages and 10X images of control and NSCLC tumor tissue sections stained with DAPI or antibodies against the indicated proteins. The yellow rectangles in Montages denote the regions shown in 10X images. Scale bar: montage, 1 mm; 10X, 20 μm. Protein levels were quantified with cellSens dimension software (Olympus). The values shown in the graphs are averages of signals quantified from six control and NSCLC independent tissue slides, respectively. Signals were calculated as described in Methods. Data are plotted as mean {plus minus} SD. For statistical analysis, the levels in treated tumors were compared to the levels in untreated tumors with a Welch 2-sample t-test. **, p-value < 0.005.</p>
Funding
Cancer Prevention and Research Institute of Texas
History
ARTICLE ABSTRACT
Tumors 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 rate-limiting 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.
These findings show that elevated heme availability due to increased heme synthesis and uptake causes intensified oxygen consumption and ATP generation, promoting tumorigenic functions and tumor growth in NSCLC.
