Karin Scarpinato Lab

Mismatch repair (MMR) proteins play a dual role as tumor suppressors.  Their repair function ensures genome stability, while their participation in a DNA damage response pathway initiates cell death of damaged cells after exposure to chemotherapeutic agents.  Defects in MMR proteins result in increased genome instability and evasion of apoptosis, promoted carcinogenesis failure of chemotherapeutic treatment and secondary tumor growth with an often selective growth advantage of MMR-deficient cancer cells under treatment conditions.

Research in the lab is focused on two main projects: (1) the mechanistic aspects of the DNA damage response pathway and its coordination with DNA repair, and (2) the contribution, detection and identification of MMR defects in non-HNPCC tumors. 

Mismatch Repair Proteins in Response to Mutagens: Implications for Carcinogenesis and Chemoresistance

We hypothesize that (1) MutS homologous (MSH) proteins are pivotal in the decision between cell death and survival upon cellular insult, that (2) different functions of MutS proteins are required for the decision between either pathway, that (3) these functional requirements rely on distinct conformational changes that trigger different protein interactions or interactions with different effect or proteins resulting in the initiation of either response and (4) that we can identify a specific MMR-dependent apoptotic pathway.   

This project will determine the DNA damage signaling cascade initiated by MMR proteins, and its distinction from the repair process.

The overall goal of this project is to obtain insights into the functional role of mismatch repair proteins at the decision point between cell death and repair.  Cell biological, biochemical, organic synthesis and biophysical tools are used to determine the apoptotic signaling cascade induced by MMR proteins.  An improved understanding of this functional role of mismatch repair proteins will provide valuable diagnostic and prognostic tools that contribute to an improved cancer treatment with less life-threatening side effects and enhanced patient survival. 

We are using computational network modeling to determine the participants in the MMR-dependent apoptosis initiated by individual chemotherapeutic agents (collaboration with F. Salsbury, Physics).

Along this line, we are interested in the structural requirements of MMR-dependent cytotoxic response and its potential for novel drug design (collaboration with F. Salsbury, Physics).  We are using computational modeling to determine differences in protein-DNA interactions and the consequences for the recruitment of downstream proteins that result in the induction of differential pathways.  Interactions with damage resulting from treatment with different chemotherapeutic drugs will be analyzed and compared.  The combination of computational structural modeling and biological tools (cell biology and biochemistry) will allow the categorization of drugs into different response pathways. 

Biophysical methods are used to dissect the molecular characteristics of protein-DNA interactions as determinants of different response pathways.  Atomic force microscopy, total internal reflection fluorescence and fluorescence resonance energy transfer are utilized to distinguish the molecular characteristics of repair and cell death events (collaboration with M. Guthold, J. Macosko, Physics).

We will utilize the information on the requirements for MMR-dependent apoptosis to provide novel approaches to chemotherapy that is based on specific targeting of a cell death pathway based on computational modeling.  We recently identified small molecules as inducers of MMR-dependent apoptosis and are currently refining these compounds to obtain the best apoptotic inducers (collaboration with F. Salsbury, Physics, B. King, Chemistry)

Taken together, these results will significantly impact chemotherapy by providing valuable information for improved prevention, intervention and targeting, with reduced chemoresistance and reduced side effects for patients.

MMR protein elevation as a marker for aggressive cancer

Cancer is the result of an accumulation of genetic alterations and mutations that lead to the transformation of a normal cell into a malignant one.  Mutations can occur spontaneously.  During replication, nucleotide selection and DNA polymerase proofreading activity confer an error rate of about 10^-7.  Replication errors that escape these verification steps are substrates for the mismatch repair (MMR) system, which adds an additional 50-1000-fold increase in fidelity.  MMR defects result in an accumulation of mutations that are associated with several types of human cancers and diseases.  While their contribution to gastrointestinal tumors is well studied, the participation of MMR defects in the development of tumors of different tissue origin is not well characterized. An increasing pool of literature is accumulating that describes such contribution.  Very few studies have investigated the contribution of MMR defects to prostate tumorigenesis.  Primarily, loss of MSH2 has been connected with prostate cancer.  In contrast, our preliminary results suggest that an elevation in one of the less characterized MMR proteins, PMS2, confers genome instability and is associated with prostate cancer; this may present an early event in prostate tumorigenesis. 

We are identifying novel targets for the prevention and treatment of prostate cancer and its consequences.  This study builds on our preliminary data that identified a novel biomarker for disease recurrence in prostate cancer patients.  We will utilize this knowledge and determine the mechanism behind this observation as a means to identify targets for the treatment of aggressive prostate cancer.

We have previously shown that the mismatch repair (MMR) protein PMS2 is significantly elevated in prostate cancer, that this elevation is correlated with poor disease outcome, and that this marker can be detected in biopsy samples and tumor-surrounding benign tissue.  At least three target areas can be identified: (1) the mechanism by which PMS2 elevation occurs, (2) the mechanism that allows selective propagation of cells with elevated PMS2, and (3) the downstream consequences of PMS2 elevation.