Faculty Bibliography

Prostate cancer (PCa) incidence and mortality rate vary among racial and ethnic groups with the highest occurrence in African American (AA) men who have mortality rates twice that of Caucasians (CA). In this study, we focused on differential expression of proteins in AA prostate cancer compared to CA using Protein Pathway Array Analysis (PPAA), in order to identify protein biomarkers associated with PCa racial disparity. Fresh frozen prostate samples (n=90) obtained from radical prostatectomy specimens with PCa, including 25 AA tumor, 21 AA benign, 23 CA tumor, 21 CA benign samples were analyzed. A total of 286 proteins and phosphoproteins were assessed using PPAA. By PPAA analysis, 33 proteins were found to be significantly differentially expressed in tumor tissue (n=48, including both CA and AA) in comparison to benign tissue (n=42). We further compared protein expression levels between AA and CA tumor groups and found that 3 proteins were differentially expressed (P<0.05 and q<5%). Aurora was found to be significantly increased in AA tumors, while Cyclin D1 and HNF-3a proteins were downregulated in AA tumors. Predicted risk score was significantly different between AA and CA ethnic groups using logistic regression analysis. In conclusion, we identified Aurora, Cyclin D1 and HNF-3a proteins as being differentially expressed between AA and CA in PCa tissue. Our study suggests that these proteins might be involved in different pathways that lead to aggressive PCa behavior in AA patients, potentially serving as biomarkers for the PCa racial disparity.

Recently, several targeted agents have been developed for specific subsets of patients with acute myeloid leukaemia (AML), including midostaurin, the first FDA-approved FLT3 inhibitor for newly diagnosed patients with FLT3 mutations. However, in the initial Phase I/II clinical trials, some patients without FLT3 mutations had transient responses to midostaurin, suggesting that this multi-targeted kinase inhibitor might benefit AML patients more broadly. Here, we demonstrate submicromolar efficacy of midostaurin in vitro and efficacy in vivo against wild-type (wt) FLT3-expressing AML cell lines and primary cells, and we compare its effectiveness with that of other FLT3 inhibitors currently in clinical trials. Midostaurin was found to synergize with standard chemotherapeutic drugs and some targeted agents against AML cells without mutations in FLT3. The mechanism may involve, in part, the unique kinase profile of midostaurin that includes proteins implicated in AML transformation, such as SYK or KIT, or inhibition of ERK pathway or proviability signalling. Our findings support further investigation of midostaurin as a chemosensitizing agent in AML patients without FLT3 mutations.

BACKGROUND:Cancer-initiating cell (CIC), a functionally homogeneous stem-like cell population, is resonsible for driving the tumor maintenance and metastasis, and is a source of chemotherapy and radiation-therapy resistance within tumors. Targeting CICs self-renewal has been proposed as a therapeutic goal and an effective approach to control tumor growth. BMI-1, a critical regulator of self-renewal in the maintenance of CICs, is identified as a potential target for colorectal cancer therapy. METHODS:Colorectal cancer stem-like cell lines HCT116 and HT29 were used for screening more than 500 synthetic compounds by sulforhodamine B (SRB) cell proliferation assay. The candidate compound was studied in vitro by SRB cell proliferation assay, western blotting, cell colony formation assay, quantitative real-time PCR, flow cytometry analysis, and transwell migration assay. Sphere formation assay and limiting dilution analysis (LDA) were performed for measuring the effect of compound on stemness properties. In vivo subcutaneous tumor growth xenograft model and liver metastasis model were performed to test the efficacy of the compound treatment. Student's t test was applied for statistical analysis. RESULTS:We report the development and characterization of a small molecule inhibitor QW24 against BMI-1. QW24 potently down-regulates BMI-1 protein level through autophagy-lysosome degradation pathway without affecting the BMI-1 mRNA level. Moreover, QW24 significantly inhibits the self-renewal of colorectal CICs in stem-like colorectal cancer cell lines, resulting in the abrogation of their proliferation and metastasis. Notably, QW24 significantly suppresses the colorectal tumor growth without obvious toxicity in the subcutaneous xenograft model, as well as decreases the tumor metastasis and increases mice survival in the liver metastasis model. Moreover, QW24 exerts a better efficiency than the previously reported BMI-1 inhibitor PTC-209. CONCLUSIONS:Our preclinical data show that QW24 exerts potent anti-tumor activity by down-regulating BMI-1 and abrogating colorectal CICs self-renewal without obvious toxicity in vivo, suggesting that QW24 could potentially be used as an effective therapeutic agent for clinical colorectal cancer treatment.

The extent of PTEN loss that confers clinical and biological impact in melanoma is unclear. We evaluated the clinical and biologic relevance of PTEN dosage in melanoma, and tested the postulate that partial PTEN loss is due to epigenetic mechanisms. PTEN expression was assessed by immunohistochemistry in a stage III melanoma cohort (n=190) with prospective follow up. 21/190 (11%) of tumors had strong PTEN expression, 51/190 (27%) had intermediate PTEN, 44/190 (23%) had weak PTEN, and 74/190 (39%) had absent PTEN. Both weak and absent PTEN expression predicted shorter survival in multivariate analyses (HR 2.13, p<0.01). We demonstrate a continuous negative correlation between PTEN and activated Akt in melanoma cells with titrated PTEN expression and in two additional independent tumor datasets. PTEN genomic alterations (deletion, mutation), promoter methylation, and protein destabilization did not fully explain PTEN loss in melanoma, whereas PTEN levels increased with treatment of melanoma cells with the histone deacetylase inhibitor LBH589. Our data indicate that partial PTEN loss is due to modifiable epigenetic mechanisms and drives Akt activation and worse prognosis, suggesting a potential approach to improve the clinical outcome for a subset of advanced melanoma patients.

The antileukaemic drug 6-mercaptopurine is converted into thioguanine nucleotides (TGN) and incorporated into DNA (DNA-TG), the active end metabolite. In a series of genome-wide association studies, we analysed time-weighted means (_wm) of erythrocyte concentrations of TGN (Ery-TGN) and DNA-TG in 1009 patients undergoing maintenance therapy for acute lymphoblastic leukaemia (ALL). In discovery analyses (454 patients), the propensity for DNA-TG incorporation (_wmDNA-TG/_wmEry-TGN ratio) was significantly associated with three intronic SNPs in NT5C2 (top hit: rs72846714; P = 2.09 × 10^-10, minor allele frequency 15%). In validation analyses (555 patients), this association remained significant during both early and late maintenance therapy (P = 8.4 × 10^-6 and 1.3 × 10^-3, respectively). The association was mostly driven by differences in _wmEry-TGN, but in regression analyses adjusted for _wmEry-TGN (P < 0.0001), rs72846714-A genotype was also associated with a higher _wmDNA-TG (P = 0.029). Targeted sequencing of NT5C2 did not identify any missense variants associated with rs72846714 or _wmEry-TGN/_wmDNA-TG. rs72846714 was not associated with relapse risk, but in a separate cohort of 180 children with relapsed ALL, rs72846714-A genotype was associated with increased occurrence of relapse-specific NT5C2 gain-of-function mutations that reduce cytosol TGN levels (P = 0.03). These observations highlight the impact of both germline and acquired mutations in drug metabolism and disease trajectory.

We report recent progress in the development of a precision test for individualized use of the VEGF-A targeting drug bevacizumab for treating ovarian cancer. We discuss the discovery model stage (i.e., past feasibility modeling and before conversion to the production test). Main results: (a) Informatics modeling plays a critical role in supporting driving clinical and health economic requirements. (b) The novel computational models support the creation of a precision test with sufficient predictivity to reduce healthcare system costs up to $30 billion over 10 years, and make the use of bevacizumab affordable without loss of length or quality of life.

MTOR COORDINATES GROWTH SIGNALS WITH METABOLIC PATHWAYS AND PROTEIN SYNTHESIS, AND IS HYPERACTIVATED IN MANY HUMAN CANCERS MTOR EXISTS IN TWO COMPLEXES, MTORC1 THAT STIMULATES PROTEIN, LIPID AND RIBOSOME BIOSYNTHESIS, AND MTORC2 THAT REGULATES CYTOSKELETON FUNCTIONS WHILE MTOR IS KNOWN TO BE INVOLVED IN THE DNA DAMAGE RESPONSE, LITTLE IS ACTUALLY KNOWN REGARDING THE FUNCTIONS OF MTORC1 COMPARED TO MTORC2 IN THIS REGARD, OR THE RESPECTIVE IMPACT ON TRANSCRIPTIONAL VERSUS TRANSLATIONAL REGULATION WE SHOW THAT MTORC1 AND MTORC2 ARE BOTH REQUIRED TO ENACT DNA DAMAGE REPAIR AND CELL SURVIVAL, RESULTING IN INCREASED CANCER CELL SURVIVAL DURING DNA DAMAGE TOGETHER MTORC1 AND 2 ENACT COORDINATED TRANSCRIPTION AND TRANSLATION OF PROTECTIVE CELL CYCLE, DNA REPLICATION, RECOMBINATION AND REPAIR GENES THIS COORDINATED TRANSCRIPTIONAL-TRANSLATIONAL RESPONSE TO DNA DAMAGE WAS NOT IMPAIRED BY RAPALOG INHIBITION OF MTORC1 OR INDEPENDENT INHIBITION OF MTORC1 OR MTORC2, BUT WAS BLOCKED BY INHIBITION OF MTORC1/2 ONLY MTORC1/2 INHIBITION REVERSED CANCER CELL RESISTANCE TO DNA DAMAGE AND REPLICATIVE STRESS, INCREASED TUMOR CELL KILLING AND TUMOR CONTROL BY DNA DAMAGE THERAPIES IN ANIMAL MODELS WHEN COMBINED WITH DNA DAMAGE, INHIBITION OF MTORC1/2 MORE STRONGLY BLOCKED TRANSCRIPTIONAL INDUCTION THAN TRANSLATION OF DNA REPLICATION, SURVIVAL, AND DNA DAMAGE RESPONSE MRNAS.

Androgen receptor (AR) antagonist MDV3100 is the first therapeutic approach in treating castration-resistant prostate cancer (CRPC), but tumours frequently become drug resistant via multiple mechanisms including AR amplification and mutation. Here we identify the small molecule Ailanthone (AIL) as a potent inhibitor of both full-length AR (AR-FL) and constitutively active truncated AR splice variants (AR-Vs). AIL binds to the co-chaperone protein p23 and prevents AR's interaction with HSP90, thus resulting in the disruption of the AR-chaperone complex followed by ubiquitin/proteasome-mediated degradation of AR as well as other p23 clients including AKT and Cdk4, and downregulates AR and its target genes in PCa cell lines and orthotopic animal tumours. In addition, AIL blocks tumour growth and metastasis of CRPC. Finally, AIL possesses favourable drug-like properties such as good bioavailability, high solubility, lack of CYP inhibition and low hepatotoxicity. In general, AIL is a potential candidate for the treatment of CRPC.

Aspirin is the most widely prescribed drug for the primary and secondary prevention of cardiovascular and cerebrovascular diseases. However, a large number of patients continue to experience thromboembolic events despite aspirin therapy, a phenomenon referred to as aspirin resistance or treatment failure. Aspirin resistance is often observed along with a high incidence of unstable plaque, cardiovascular events and cerebrovascular accident. Studies have shown that aspirin reduces the production of TXA2, but not totally inhibits the activation of platelets. In this review, we analyze current and past research on aspirin resistance, presenting important summaries of results regarding the potential contributive roles of single nucleotide polymorphisms, inflammation, metabolic syndrome and miRNAs. The aim of this article is to provide a brief review on aspirin resistance and platelet function, which will provide important insights into the research of aspirin resistance.