Lactate Transport as a Therapeutic Target in Glioma

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DESCRIPTION (provided by applicant): An abnormally high rate of glycolysis, i.e., rapid consumption of glucose and metabolism to lactic acid, is a hallmark of all malignant tumors. Our long-term goal is to elucidate the molecular basis for this aberrant behavior, and harness that knowledge towards development of therapeutic strategies against glioblastoma multiforme (GBM), the most malignant and lethal of brain tumors. We hypothesize that inhibition of lactate efflux by these tumors will debilitate their metabolism and cause their death, based on our observations that 1] lactic acid is effluxed to the tumor microenvironment in large quantities by GBMs, 2] specific lactate transporter isoforms are highly expressed in GBMs in contrast to normal brain tissue, 3] inhibition of lactate transporter expression or their function in GBM derived cell lines, both in vitro and in vivo, halted their ability to efflux lactic acid, and resulted in their rapid destruction. The specific aims are to: 1. Identify the key signaling pathways that regulate lactate transporter expression in GBMs. Promoter of MCT2, the lactate transporter predominantly expressed in GBMs, will be used as the model to distinguish the primary metabolites and trans-activating factors that are involved. 2. Investigate how lactate efflux affects the invasive potential of GBMs. Lactic acid was recently identified to influence the remodeling of extracellular matrix by tumors. We will query the glioma micro-environment via organotypic brain-slice cultures for induction of key stromal and tumor-derived proteases by lactic acid, and correlate the effects on the invasive process. 3. Examine how signaling pathways common to erythropoiesis interact with the MCT2 promoter. Cis-acting elements common in erythropoietic genes are the most prolific on the proximal MCT2 promoter. We will investigate how these motifs and their trans-acting factors regulate MCT2 expression in GBMs, and the rationale for their presence. 4. Develop an in vitro cellular assay for rapid screening of small molecule drugs to identify novel lactate transporter inhibitors. Derivatives of cinnamic acid are the only known competitive inhibitors of lactate transporters. We will utilize gel micro-encapsulated-cell based techniques to design an in vitro assay for screening of small molecule chemical libraries to identify new drugs to target lactate transport. Every year more than 17,000 people in the US, mostly children 3 to 12 years old, and adults 40 to 70 years old, find out they have malignant brain cancer. Tragically, 90% of them still die within 6 to 12 months, even after surgery, radiation treatment, and chemotherapy. Thus, we need new ways to target this deadly cancer. We plan to test a novel method to "pickle-the-tumor-to-death," while leaving healthy brain cells intact.