Browsing by Author "Sohoni, Sagar"
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Item Broadband Transient Absorption Study of Photoexcitations in Lead Halide Perovskites: Towards a Multiband Picture(2016-02-24) Alam, Md Maksudul; Sohoni, Sagar; Kalainayakan, Sarada Preeta; Garrossian, Massoud; Zhang, Li; 0000-0001-9242-0763 (Zhang, L); Alam, Md Maksudul; Sohoni, Sagar; Kalainayakan, Sarada Preeta; Zhang, LiBACKGROUND: Aberrant Hedgehog (Hh) signaling is associated with the development of many cancers including prostate cancer, gastrointestinal cancer, lung cancer, pancreatic cancer, ovarian cancer, and basal cell carcinoma. The Hh signaling pathway has been one of the most intensely investigated targets for cancer therapy, and a number of compounds inhibiting Hh signaling are being tested clinically for treating many cancers. Lung cancer causes more deaths than the next three most common cancers (colon, breast, and prostate) combined. Cyclopamine was the first compound found to inhibit Hh signaling and has been invaluable for understanding the function of Hh signaling in development and cancer. To find novel strategies for combating lung cancer, we decided to characterize the effect of cyclopamine tartrate (CycT), an improved analogue of cyclopamine, on lung cancer cells and its mechanism of action. METHODS: The effect of CycT on oxygen consumption and proliferation of non-small-cell lung cancer (NSCLC) cell lines was quantified by using an Oxygraph system and live cell counting, respectively. Apoptosis was detected by using Annexin V and Propidium Iodide staining. CycT’s impact on ROS generation, mitochondrial membrane potential, and mitochondrial morphology in NSCLC cells was monitored by using fluorometry and fluorescent microscopy. Western blotting and fluorescent microscopy were used to detect the levels and localization of Hh signaling targets, mitochondrial fission protein Drp1, and heme-related proteins in various NSCLC cells. RESULTS: Our findings identified a novel function of CycT, as well as another Hh inhibitor SANT1, to disrupt mitochondrial function and aerobic respiration. Our results showed that CycT, like glutamine depletion, caused a substantial decrease in oxygen consumption in a number of NSCLC cell lines, suppressed NSCLC cell proliferation, and induced apoptosis. Further, we found that CycT increased ROS generation, mitochondrial membrane hyperpolarization, and mitochondrial fragmentation, thereby disrupting mitochondrial function in NSCLC cells. CONCLUSIONS: Together, our work demonstrates that CycT, and likely other Hh signaling inhibitors, can interrupt NSCLC cell function by promoting mitochondrial fission and fragmentation, mitochondrial membrane hyperpolarization, and ROS generation, thereby diminishing mitochondrial respiration, suppressing cell proliferation, and causing apoptosis. Our work provides novel mechanistic insights into the action of Hh inhibitors in cancer cells.Item Increased Heme Flux and Mitochondrial Resporation Enhance Tumorigenic Functions in Non-Small Cell Lung Cancer Cells(2019-12) Sohoni, Sagar; Zhang, LiLung cancer is the leading cause of cancer related deaths in United States, and about 85% of the cases are Non-small cell lung cancer (NSCLC). Many targeted therapies have been developed to treat lung cancer. Unfortunately, however statistical data over the past two decades suggest only a slight improvement in a patient’s survival rate after diagnosis. Clonal evolution and tumor heterogeneity are the major obstacles in designing effective targeted treatments against cancer. To create more comprehensive treatments, emerging therapies target bioenergetic pathways of cancer cells. Like normal cells, cancer cells can generate energy only through glycolysis and oxidative phosphorylation. Notably, a number of studies have shown that many types of cancer cells rely heavily on mitochondrial respiration. Tumors of human non-small cell lung cancer (NSCLC) are heterogeneous but exhibit elevated glycolysis and glucose oxidation relative to benign lung. Heme is a central molecule for oxidative metabolism and ATP generation via mitochondrial oxidative phosphorylation (OXPHOS). Here, we have found that non-small cell lung cancer cells show elevated levels of heme synthesis and uptake, mitochondrial heme, oxygen-utilizing hemoproteins, oxygen consumption, ATP generation, and key mitochondrial biogenesis regulators relative to non-tumorigenic cells. Likewise, proteins and enzymes relating to heme and mitochondrial functions are found to be upregulated in human NSCLC tissues relative to normal tissues. Hence, we believe altering heme availability can be a useful strategy in treatment of highly heterogenous cancers. In order to seqester extra-cellular heme we engineered heme-sequestering peptides (HSPs). We observed that treatment with HSPs significantly reduce heme uptake, intracellular heme levels, and tumorigenic functions of NSCLC cells. This effect of HSPs is specific to heme as addition of heme largely reversed the effect of HSPs on tumorigenic functions. Furthermore, we also observed that HSP2 significantly suppresses the growth of human NSCLC xenograft tumors in mice. HSP2-treated tumors showed lowered oxygen consumption rates and ATP levels. To further verify the importance of heme in promoting tumorigenicity, we generated NSCLC cell lines with increased heme synthesis or uptake, which result from overexpression of 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 have elevated oxygen consumption rates and ATP levels. Our data show that elevated heme flux and function underlie enhanced OXPHOS and tumorigenicity of NSCLC cells. Therefore, targeting heme flux and function offers a novel strategy for developing lung cancer therapy.