Targeting the Warburg Effect in Kidney Cancer

Over 79,000 people will develop kidney cancer, also known as renal cell carcinoma (RCC), and almost 14,000 patients will die from this disease in the US this year. Risk factors such as tobacco smoking, obesity and exposure to organic solvents, heavy metals, herbicides, and petrochemicals, all play a major role in

the development of RCC. Members of the military and their families are at risk of developing RCC because of exposure to these risk factors: 1) Cheap tobacco prices have been identified by enlisted personnel and Department of Defense health policy experts as promoting a culture of tobacco use in the US Military.

Smoking doubles the risk of RCC in the members of the military; 2) Higher incidence of RCC in men versus women (2:1 ratio); 3) Incidence of RCC in veterans of Operation Ranch Hand, the unit responsible for aerially spraying herbicides in Vietnam. 4) Obesity among the non-active duty; 5) Military families are at

risk because of environmental exposures. In terms of treatment, traditional radiation and chemotherapies are ineffective and ~50% of patients develop metastatic disease, for whom the 5-year survival rate is only ~10%. Such grim statistics point to an urgent need for deeper understanding of the RCC biology and also

for developing better therapeutic strategies. Clear Cell Renal Cell Carcinoma (ccRCC), the most common type of renal cancer, is resistant to conventional radiotherapy and chemotherapy. This subtype of kidney cancer uses aerobic glycolysis to convert glucose to pyruvate and then lactate, a phenomenon known as

the “Warburg effect”. Lactate dehydrogenase-A (LDHA) is the key enzyme in converting pyruvate to lactate in order to speedily produce ATP. LDHA has Althouwith gh been shown to be an attractive target in ccRCC therapy, LDHA inhibitors have yet to see meaningful clinical advancement. This is in part due to a lack of

LDH isoform selectivity. We have recently reported that the tumor suppressor FLCN function as an intra- cellular specific inhibitor of LDHA but not LDHB. Our data has shown that a MAPK signaling pathway is responsible for FLCN phosphorylation, inactivation and dissociation from LDHA. This is important for the

hyperactivity of LDHA and conversion of pyruvate to lactate. However, the detailed mechanism of this process in ccRCC remains elusive. Additionally, we have created a cyclic decapeptide derived from the FLCN which is protected from cellular proteases, but without losing its inhibitory activity towards LDHA.

This peptide readily enters cells, inhibit LDHA and cause apoptosis in ccRCC. The long-term goal of this project is to improve outcomes for patients with ccRCC by developing therapeutic strategies that targets LDHA. The overall objective is to determine the signaling networks involved in FLCN inactivation, disas-

sociation and hyperactivity of LDHA in ccRCC. The central hypothesis is that MAPK mediated phosphory- lation of FLCN leads to its inactivation, disassociation and hyperactivity of LDHA. The rationale of this proposal is that by dissecting these regulatory networks, we could design a strategy to specifically inhibit

LDHA. Biochemical, biophysical, cell-based assays, and patient derived ccRCC tumor xenograft model as well and the ccRCC tissue array will be used to test the hypothesis in the following specific aims; Aim 1: Determine the mechanism of MAPK mediated phosphorylation and inactivation of FLCN in ccRCC. Aim 2:

Determine the mechanism of MAPK activation by pyruvate stress in ccRCC. Aim 3: Evaluate the impact of FLCN mediated inhibition of LDHA in ccRCC patient-derived xenograft model. We expect that data gener- ated here will determine the molecular mechanism of the tumor suppressor FLCN inactivation and LDHA

hyperactivity and the Warburg effect in ccRCC. We also expect to demonstrate cyclic-FLCN decapeptide as potent specific inhibitor of LDHA in ccRCC. The outcome of this research will allow us to design new therapeutic strategies in treating Veterans with kidney cancer and potentially other cancers that experience

the Warburg effect.