Military Relevance and Unmet Need: Colorectal cancer is the third most prevalent type of cancer diagnosed with the second highest mortality rate worldwide. The Department of Veterans Affairs considers colorectal cancer to be a presumptive disease for military personnel and Veterans exposed to ionizing radiation. Military personnel, Veterans, and their families are also exposed to higher levels of other carcinogens from tobacco, processed food and red meat compared to civilians, leading to considerable risk of developing colorectal cancer. Based on the low 5-year survival rates for patients diagnosed with late-stage and metastatic colorectal cancer (11%-14%), it is very clear that the standard of care drug therapy is ineffective. Patients must often endure the severe adverse effects of these drug therapies with the limited hope that it will merely slow tumor growth, and almost no hope in preventing the spread of metastasis. Thus, more effective drug therapies are a critical unmet need for metastatic late-stage colorectal cancer patients. Our long-term goal is to develop effective drug combination therapies to greatly improve late-stage colorectal cancer overall survival and to improve the quality of life for military beneficiaries and civilians suffering from metastatic colorectal cancer.

Our Approach to Achieve Our Long-Term Goal: Epithelial-mesenchymal transition (EMT) is a reversible cellular process that allows adherent epithelial cells to transform into invasive and highly mobile mesenchymal cells. During colorectal cancer progression, aberrant EMT is linked as a major driving force promoting malignant cancer with drug resistance and metastasis. In fact, EMT is well accepted by the cancer research field to be a dominant driving force for the most prominent human cancers such as lung and breast cancer. Despite this acceptance, there has been limited success in developing drug therapies that specifically target the cellular proteins promoting EMT. This is largely due to a lack of known druggable targets and their exact role in regulating or promoting EMT in cancer. As a result of our previously funded Department of Defense grant (DoD), we have identified and validated the well-known cancer target, topoisomerase II alpha (TOP2A), as a required component for T-Cell Factor (TCF) gene regulation. We have characterized TOP2A-dependent TCF gene regulation as a master regulator of EMT, promoting the expression of a plethora of mesenchymal or metastatic genes in colorectal cancer. Moreover, we have validated that ATP-competitive small molecule inhibitors, are effective at inhibiting TOP2A-dependent TCF-mediated metastatic gene expression. Importantly, we and others demonstrate that ATP is required by TOP2A for TCF-gene expression. Thus, inhibiting ATP from binding TOP2A inhibits TCF-mediated gene expression, which in turn reverses EMT, promoting a more benign cancer that is sensitized to clinically relevant cancer drugs. We also show that ATP-competitive inhibitors that reverse EMT inhibit or suppress colorectal cancer cell invasion. Therefore, we hypothesize that our EMT targeting agents, AA-207 and AA-163, that reverse EMT by inhibiting TCF-mediated gene expression will be an effective therapeutic strategy in combination with chemotherapy and targeted antitumor drugs. We anticipate that our EMT-targeting agents will sensitize tumors to clinically relevant drugs and inhibit metastasis.

Specific Aims: To achieve our long-term goal and test our hypothesis, we will conduct combination efficacy studies using EMT targeting agents AA-207 and AA-163, and 20 clinically relevant Cancer Therapy Evaluation Program (CTEP) drugs. CTEP is a major initiative administered by the National Institutes of Health (NIH) National Cancer Institute (NCI). In Aim 1: we will evaluate the antitumor potential of AA-207 and AA-163 as combination therapies with 20 different CTEP drugs. In Aim 2: we will validate EMT targeting agent/CTEP drug combinations using patient-derived tumor xenograft (PDTX) models of colorectal cancer tumor growth and metastasis. The PDTX model is ideal because it maintains tumor heterogeneity and recapitulates human tumors growth and function compared to cancer cell lines xenografts due to excessive in vitro cell culture.

Expected Outcomes: After successful completion of this 2-year research proposal, we expect to validate two or more drug combinations effective against metastatic colorectal cancer. CTEP drugs are Food and Drug Administration-approved or investigational new drugs, and the CTEP in conjunction with Experimental Therapeutics Clinical Trials Network (ETCTN) is designed to efficiently study the safety and clinical activity of new agents and novel combinations in early phase clinical trials (phase 0-1). Furthermore, the University of Colorado Cancer Center hosts a CTEP UM1 consortium grant in collaboration with MD Anderson Cancer Center to conduct early phase clinical trials. Thus, after successful completion of the proposed DoD expansion grant, we have a direct mechanism to facilitate translation of outcomes resulting from the proposed research.