Drug Tolerant Persisters (DTP)s

Colorectal cancer is the third most common cause of cancer-related deaths globally. DTPs, cells in a conserved and transient state of chemotherapy tolerance, provide a new avenue to target colorectal cancer tumors before genetic chemoresistance develops. Our research focuses on better understanding DTPs and identifying genes, proteins and pathways that can be manipulated to specifically target cells and tumors in the DTP-state.

Research Topics

Autophagy and Apoptosis

DTP-state colorectal cancer cells can hijack the autophagy and apoptosis pathways to avoid killing by chemotherapy. We aim to identify proteins at the intersection of autophagy and apoptosis to effectively target both pathways and prohibit the ability of DTPs to survive treatment.

  • To better understand the molecular mechanisms that cancer cells use to initiate and maintain the DTP-state, we aim to describe how autophagy is being upregulated, while apoptosis is simultaneously inhibited. We are specifically interested in the interaction between Beclin and Bcl2 family members, whose interaction is known to play a role in both the initiation of autophagy and the inhibition of apoptosis.

RNA Biology and Metabolism

The transcriptome of DTP cells is dramatically dysregulated. We are interested in examining upstream RNA interactors, specifically microRNA (miRNA) and RNA modifications to identify the role of RNA biology and metabolism in generating and maintaing DTPs.

  • RNA Modifications: DTPs are hypotranscriptive (have less RNA than control tumors). One of the main mechanisms that regulates RNA stability and degradation are RNA modifications. Recent literature in mouse models of diapause have suggested that hypotranscription is induced through dysregulated RNA modification. We are currently working to identify the roles of RNA modification in our model of DTP.

    microRNA (miRNA): miRNAs have the ability to coordinate simultaneous expression/inhibition of multiple genes. miRNAs are also known to play a role in chemoresistance, however their roles in DTPs are poorly understood. We are interested in determining if/which miRNAs are playing a role in initiating the DTP-state with the hope of modulating their RNA targets.

Cholesterol Biosynthesis

One of the main pathways altered in DTP cells is cholesterol biosynthesis, specifically cholesterol efflux. We are interersted in examining the role of cholesterol biosynthesis in maintaining DTPs with hopes that we can one day manipulate the pathway to specifically target DTPs.

  • Cholesterol is a key regulator in maintaining the integrity of the cytoplasm and the fluidity of the plasma membrane. As cholesterol efflux is one of the most differentially regulated pathways in DTPs, we are currently investigating the roles of cholesterol in maintaining cells in the DTP-state.

Model Expansion

Our lab primarily focuses on DTPs in colorectal cancer, however we believe DTPs can be found in a variety of cancers, particularly those that are prone to chemoresistance. We are working on deepening our understanding of DTP biology by expanding into other cancer models.

  • Breast Cancer: Approximately 13% of females will develop breast cancer throughout their lifetime and, like colorectal cancer, these individuals are at high risk for developing chemoresistance. We are currently working with 2 breast cancer models (BT474 & MDA-MB-231) to determine if they are able to initiate entry into DTP upon chemotherapy treatment. These experiments will further our understanding of both DTPs and the development of chemoresistance in breast cancer.

    Syngeneic Mouse Models: The majority of mouse experiments lack a functional immune system. We are currently in the process of generating syngeneic models (CT26 & MC38) of DTP to better understand the role of immunity in DTP initiation, maintenance and exit.

Screening Platforms

Like all cancer cells, DTPs are tricky to target. We are developing multiple screens to identify the specific proteins involved in their survival. Currently, we are focused on an EPI-drug library, and a miRNA screen. We are also in the processes of generating a drug-screen using patient samples.

  • Epi-Drug Library Screen: Using an epi-drug library provided to us by Dr. Hansen He’s lab, we are performing a CRISPR-knockout screen to determine the (druggable) proteins involved in DTP maintenance.

    miRNA Screen: Similar to the epi-drug screen, we will be performing a miRNA CRISPR-knockout screen to determine the specific miRNAs important on initiating and/or maintaining cells in DTPs.

Signature Development

Nearly all patients with colorectal cancer will unfortunately suffer from tumor relapse. Using our sequencing data, we aim to develop a ‘DTP-signature’ that can be implemented in clinic to identify patients more likely to require future intervention.

  • Coming soon…