ABSTRACT
BACKGROUND: Metabolic plasticity mediates breast cancer survival, growth, and immune evasion during metastasis. However, how tumor cell metabolism is influenced by and feeds back to regulate breast cancer progression are not fully understood. We identify hypoxia-mediated suppression of pyruvate carboxylase (PC), and subsequent induction of lactate production, as a metabolic regulator of immunosuppression. METHODS: We used qPCR, immunoblot, and reporter assays to characterize repression of PC in hypoxic primary tumors. Steady state metabolomics were used to identify changes in metabolite pools upon PC depletion. In vivo tumor growth and metastasis assays were used to evaluate the impact of PC manipulation and pharmacologic inhibition of lactate transporters. Immunohistochemistry, flow cytometry, and global gene expression analyzes of tumor tissue were employed to characterize the impact of PC depletion on tumor immunity. RESULTS: PC is essential for metastatic colonization of the lungs. In contrast, depletion of PC in tumor cells promotes primary tumor growth. This effect was only observed in immune competent animals, supporting the hypothesis that repression of PC can suppress anti-tumor immunity. Exploring key differences between the pulmonary and mammary environments, we demonstrate that hypoxia potently downregulated PC. In the absence of PC, tumor cells produce more lactate and undergo less oxidative phosphorylation. Inhibition of lactate metabolism was sufficient to restore T cell populations to PC-depleted mammary tumors. CONCLUSIONS: We present a dimorphic role for PC in primary mammary tumors vs. pulmonary metastases. These findings highlight a key contextual role for PC-directed lactate production as a metabolic nexus connecting hypoxia and antitumor immunity.
Subject(s)
Breast Neoplasms , Pyruvate Carboxylase , Pyruvate Carboxylase/metabolism , Pyruvate Carboxylase/genetics , Animals , Female , Mice , Humans , Breast Neoplasms/pathology , Breast Neoplasms/metabolism , Breast Neoplasms/genetics , Breast Neoplasms/immunology , Cell Line, Tumor , Lactic Acid/metabolism , Gene Expression Regulation, Neoplastic , Cell Hypoxia , Lung Neoplasms/metabolism , Lung Neoplasms/pathology , Lung Neoplasms/genetics , Immune ToleranceABSTRACT
Breast cancer is the most common cancer in women. The upregulation of insulin-like growth factor (IGF) system observed in certain types of breast cancers was linked to growth, metastasis, and survival resulting in multiple strategies designed to target the type I IGF receptor (IGF-1R) in breast cancer. These attempts failed to prove beneficial and it has been suggested that insulin receptor (IR) could also play an important role in breast cancer biology. To better understand the IR's role in breast cancer cells, the receptor was deleted from MCF-7L cells using CRISPR technology, and fluorescence-assisted cell sorting was used to obtain clone 35 (CL35). It was found that CL35 activated signaling pathways upon insulin stimulation despite the absence of IR expression. We hypothesized that CL35 used a surrogate receptor for sustained growth and development. IGF-1R was able to activate insulin signaling and growth in CL35. Thus, insulin may play a central role in regulating breast cancer growth due to its ability to activate all the receptors of the IGF family. These findings argue that dual targeting of IR and IGF-IR may be required to inhibit breast cancer growth.
Subject(s)
Breast Neoplasms , Receptor, Insulin , Female , Humans , Breast Neoplasms/metabolism , Cell Line, Tumor , Insulin/pharmacology , Insulin-Like Growth Factor I/metabolism , Receptor, IGF Type 1/genetics , Receptor, IGF Type 1/metabolism , Receptor, Insulin/genetics , Receptor, Insulin/metabolism , Receptors, Somatomedin/geneticsABSTRACT
Aim was to fabricate and optimize CUR-loaded mannose-functionalized chitosan nanoparticles (Cur-MCN) which overcome the limitations of drugs to reach the intracellular locations and to establish its therapeutic potential in visceral leishmaniasis by targeting of CUR to macrophages. Cur-MCN were developed by mannose-conjugated chitosan and have been tested for their efficacy and toxicit. In vivo antileishmanial activity in hamsters has shown significantly greater suppression of parasite replication in the spleen with Cur-MCN than unconjugated chitosan nanoparticles. The in vitro cytotoxicity study against the J774A.1 cell line demonstrated its comparative non-toxicity towards the macrophage cells. The potential of Cur-MCN was also confirmed by minimal observed cytotoxicity in our in vivo studies.
