Therapeutic potential of targeting DNA repair deficiency in TSC

PROJECT SUMMARY/ ABSTRACT Using next-generation sequencing, researchers have identified somatic mutations as essential for tumor etiology and evolution. We now know that many cancers also have a substantial germline component. Germline mutations increase the lifetime risk of cancer and often result in earlier onset and more advanced disease.

A significant portion of germline cancer mutations occur in DNA damage response (DDR) genes, which lead to the failed repair of DNA lesions, the accumulation of somatic mutations and structural variants that promote oncogenesis.

In our recent genomic analysis of tuberous sclerosis (TSC) patients, we unexpectedly found that double-strand break (DSB) repair deficiencies are frequent in the germline.

TSC is a tumor syndrome characterized by mutations in the tumor suppressors, TSC1 and TSC2, causing dysregulated activation of the mTOR pathway.

Breast, ovarian, and metastatic prostate cancers also harbor pathogenic germline mutations in DDR repair genes and somatic mutations leading to hyperactive mTOR signaling.

As such, we aim to evaluate the therapeutic activity of DDR-targeted agents alone and in combination with mTOR inhibitors for reduced tumor burden in TSC, which may also provide valuable insights for cancers characterized by hyperactive mTOR signaling.

Our central hypothesis is that a defective DNA damage response cooperates with mTOR pathway activation to drive tumor growth.

We will use genome editing tools to introduce specific DSB repair variants into isogenic cell lines and then measure DNA damage and mTOR signaling.

We will assay cell viability and anchorage- independent growth to determine if DSB mutations promote clonogenic potential and survival in isogenic cells.

Further, in Specific Aim 2, we plan to explore therapeutic potential using targeted agents to DDR alone and in combination with mTOR inhibitors in vivo.

Specifically, we will use syngeneic mouse models to evaluate the efficacy of CHK inhibitors or PARP inhibitors as single agents and in combined dosing strategies with everolimus.

Through the proposed research, we will determine whether germline DSB repair defects create a unique therapeutic opportunity in mTOR-driven tumors.

Our results could have broad-reaching implications given the essential roles of germline DDR mutations and somatic mTOR pathway mutations in tumor formation and malignant lesions.