Research

The goal of my research is to understand the mechanisms of cancer progression and resistance to therapy and translate those findings into the clinic. My laboratory is currently focused on 1) testing the hypothesis that HULLK, the novel lncRNA we discovered, functions as an oncogene and a clinical biomarker in PCa; 2) testing the hypothesis that co-targeting the transcription factor ERG with AR could be an effective treatment strategy for PCa by further developing a novel small molecule ERG inhibitors; 3) leveraging a validated in vitro multi-cell tumor microenvironment system that we developed to a) determine how heterotypic cell signaling in the tumor microenvironment determines sensitivity to immune checkpoint inhibitors, and b) to evaluate the impact of heightened cortisol levels, indicative of patient psychological distress, on tumor cell proliferation and response to cancer treatments.

HULLK

In 2019, we published the discovery of a novel lncRNA that acts as an oncogene in PCa named “HULLK” for Hormone-Upregulated lncRNA within LCK. This discovery stemmed from our earlier work identifying kinases that regulate PCa cell growth and response to androgen. One hit from the RNAi phenotypic screen was the non-receptor tyrosine kinase LCK. That observation led to the discovery of the lncRNA HULLK.

Clinically, HULLK expression correlates positively with tumor grade (Gleason score), and higher HULLK expression is associated with recurrence in PCa patients. Determining the mechanisms of HULLK oncogene-like function in PCa are the foundation for developing new diagnostic, prognostic, and therapeutic approaches to combat PCa.

Many lncRNAs fold into unique structures that specifically interact with mRNAs and/or proteins to control regulatory networks within the cell. We have methodically interrogated HULLK RNA structure and binding partners to uncover potential mechanisms for HULLK action in PCa. We identified HULLK-interacting mRNAs and proteins using MS2-TRAP. We identified distinct structural domains of HULLK RNA by SHAPE-MaP chemical probing and sequencing in collaboration with Dr. Chase Wiedemann, UMich. Intermolecular duplex predictions (intaRNA) from these studies suggest that a G-rich region in HULLK is poised to pair with the target mRNAs enriched by MS2-TRAP of HULLK. Most notably, ten of the top 15 HULLK-interacting mRNAs code for proteins that play roles in cell adhesion, including three that regulate the Rho family of small GTPases. Among the top 15 proteins that interact with HULLK RNA, three are also involved in cell adhesion. Together, these data reveal a complex network of HULLK interacting mRNAs and proteins that support the hypothesis that HULLK drives PCa growth through regulating PCa adhesion. To address this hypothesis, we are 1) determining the mechanism through which HULLK regulates cell adhesion, and 2) Determine which HULLK structural domains are critical for interacting with HULLK binding partners to regulate PCa cell adhesion.

The significant positive correlation between HULLK expression and high-grade PCa suggests that HULLK is a biomarker for PCa. We have completed proof-of-concept experiments demonstrating HULLK is detectable in the urine of men with high-grade PCa. Urine is a non-invasive, easily available biological fluid. Examining HULLK levels in 68 biopsy-confirmed PCa patients and 28 age-matched normal controls, the ROC AUC = 0.72 [95% Ci:0.62–0.82]. For comparison, the AUC for serum PSA from a >5000 patient cohort was 0.678 [95% Ci:0.67–0.69] suggesting that HULLK urine levels has potential to be a superior biomarker to serum PSA, in addition to being less invasive and more easily collected. Thus, we hypothesize that HULLK urine levels function as a biomarker for the detection, risk stratification, and treatment response of PCa.

Therapeutic strategies targeting driver pathways in PCa 

The development, progression, and recurrence of PCa is dependent on the AR. Currently, anti-androgen therapies that reduce endogenous steroid hormone production and AR antagonists are used as therapeutic interventions. Unfortunately, nearly all patients receiving androgen deprivation therapy (ADT) develop resistance and progress to castration resistant PCa (CRPC). The prognosis for CRPC is poor, with median survival of ~3 years even with the most advanced medical therapy. In short, CRPC has poor treatment options and prognosis, creating a clear and significant need for new treatments. Ligand activated transcription factors (TFs) aside, TFs have traditionally been viewed as “undruggable”, although this paradigm is rapidly shifting. The targeting of TFs for drug development has tremendous potential based on their well-documented roles in cancer stemness, immune evasion, autoregulatory driver circuits, and drug resistance. The TF ERG is the predominant target of chromosomal translocations with TMPRSS2; these gene fusions are observed in ~50% of PCa patients. As the expression of TMPRSS2 is AR regulated, this gene fusion results in AR driven over-expression of ERG in these prostate cancers. Multiple model systems have confirmed the driver nature of ERG in PCa, firmly establishing ERG as a validated therapeutic target for PCa. Unfortunately, there are currently no well-validated, potent, and specific inhibitors targeting ERG. Our collaborator, Dr. John Bushweller, used a strategy of identifying compounds that stabilize the autoinhibited form of ERG by binding at a unique allosteric site to achieve inhibition of ERG-DNA binding to generate the first generation of ERG inhibitors with promising on-target mechanism of action and specificity of action. We hypothesize that small molecule inhibitors of ERG-DNA binding will abrogate the ERG driven gene expression program in PCa and provide an effective targeted therapy for the treatment of PCa driven by the TMPRSS2-ERG gene fusion. We are profiling effects of the inhibitors on PCa cell lines for proliferation, apoptosis/death, and cell cycle alterations. Effects on gene expression and ERG occupancy of well-validated target genes will be evaluated in addition to genome wide profiling of gene expression effects and ERG occupancy in the genome.

Impact of patient distress on pancreatic cancer growth and response to therapy

This collaborative project with Dr. Phil Chow utilizes a biobehavioral approach to improve cancer outcomes by providing the first rigorous test of the impact of cancer patient psychological distress through cortisol on tumor cell growth, and test whether reducing patient psychological distress improves tumor outcomes. Biobehavioral models of disease emphasize the need to understand, and ultimately address, the ways patient biological, behavioral, and psychosocial factors interact to affect disease outcomes. Adults with pancreatic ductal adenocarcinoma (PDAC) have the lowest five-year survival rate of all major cancers and experience the highest levels of distress. However, the impact of patient psychological distress on the growth and treatment of their tumors is not well understood, despite robust findings on the negative effects of stress on human physiology through cortisol. Understanding the impact of psychologically distressed patient cortisol trajectories on PDAC could lead to novel multimodal strategies that intervene on key mechanisms of PDAC at the biological and behavioral/psychosocial levels of a patient. This could address a critical gap in care, as interventions to mitigate distress in adults with PDAC are not optimized for impact and engagement. To fill this gap, researchers should develop a multipronged intervention that targets specific factors influencing distress and aligns with the attitudes and preferences of patients.

We are building on findings from our preliminary study focused on how patient psychological distress, using cortisol as a biomarker, influences tumor behavior in a validated in vitro multi-cell tumor microenvironment system (TMES). Our study was conducted in two phases. In the first phase, cortisol levels of ten distressed patients with PDAC were assessed through saliva samples collected three times a day over five days. In the second phase, the TMES was used to investigate how PDAC cells respond in the presence of cortisol trajectories in the microenvironment modeled after those of high versus normal distressed patients with PDAC. When circulating cortisol was modeled after patients with high levels of distress, there was a 33% increase in PDAC cell growth and dampened benefit of cancer therapeutics. These findings lead to the next logical step to be investigated, where we will test the impact of patient psychological distress on PDAC cell growth and response to cancer therapeutics in a larger sample of adults with PDAC, as well as test whether reducing patient psychological distress can alter PDAC cell growth and response to cancer therapeutics.

Together, each of the initiatives described above contribute to the central goal of my research program, which is to understand how crosstalk among signal transduction pathways contributes to cancer progression in complex models of disease, and how that information can be used to develop more effective cancer treatments.