Fengzhi Li - US grants

[unreadable] DESCRIPTION (provided by applicant): Survivin, a novel member of the inhibitor of apoptosis (IAP) protein family, is undetectable in most normal adult tissues but highly expressed in cancer. It has been reported that taxol-mediated mitotic arrest is associated with the induction of survivin, which preserves a survival pathway for cancer cells. However, we have made observations that challenge this paradigm. We have found that induction of survivin by taxol is an early event following taxol treatment and is independent of taxol-mediated G2/M arrest. Moreover, increasing treatment times with taxol actually reduces survivin induction in comparison with the early time-points even though the G2/M cell population increases over these periods. The data have also revealed that the early induction of survivin by taxol appears to be involved in cancer cell resistance to taxol treatment. Abrogation [unreadable] of this new survivin-associated survival pathway may provide the basis for novel approaches to eliminate cancer cells. In this proposal, we will use a number of cancer cell models to delineate the signaling pathways involved in taxol-mediated, cell cycle-independent induction of survivin and to explore the role and underlying mechanism of the rapid survivin induction by taxol in cancer cell drug resistance. Specifically, we will: 1) determine the effect of taxol on survivin induction and delineate the signaling pathways involved in taxol-mediated, cell cycle-independent survivin induction in different types of cancer cells; 2) examine the mechanistic role of taxol-mediated survivin induction in cancer cell survival; 3) evaluate the effects of inhibition of taxol-mediated survivin induction on taxol-induced cancer cell death; and 4) explore the transcriptional and post-transcriptional mechanism by which taxol upregulates survivin. These studies may extend the current understanding of the mechanisms of drug resistance and survivin action, and may reveal alternative therapeutic sites and/or targets to develop novel approaches for cancer treatment. [unreadable] [unreadable]

Our data indicate that the human prostate-derived Ets transcription factor (PDEF) plays an essential role in tumor suppression via downregulation of the expression of antiapoptotic protein survivin. Ectopic expression of PDEF in PDEF-negative breast cancer cells inhibits survivin expression as well as its promoter activity. In contrast, knockdown of PDEF in PDEF-positive breast cancer cells upregulates survivin expression along with increased cell proliferation in vitro, and increases xenograft tumor take rate and tumor growth in vivo. Importantly, patients with survivin-/PDEF+ tumor show better survival and less relapse than patients with survivin+/PDEF- tumor. Abnormal inhibition of apoptosis is known to be one of the critical steps for oncogenesis and malignant progression. Although the underlying mechanisms are not fully understood, evidence indicates that survivin plays an important role in the initiation, progression, metastasis and recurrence of cancer. Accordingly, many natural dietary components, including resveratrol, silibinin, sulindac, retinoid, selenium and vitamin D compounds that have cancer-preventive and therapeutic effects, downregulate survivin expression. PDEF appears to have an opposing role to survivin and likely via downregulation of survivin expression. It has been shown that PDEF inhibits cancer cell migration, invasion and growth. Based on these observations, we hypothesize that application of survivin and PDEF as interconnected biomarkers and targets to stratify patents with survivin+/PDEF- tumor and patients with survivin-/PDEF+ tumor may facilitate prostate cancer prognosis and personalized medicine. Two specific aims are proposed to test this hypothesis: 1) determine survivin and PDEF expression status and their association with patient survival, cancer metastasis and tumor relapse using prostate cancer tissues;and 2) determine methylation status of the PDEF gene in prostate cancer tissues and its association with the expression of PDEF and survivin. These studies may provide novel approaches for cancer prognosis and personalized medicine, by considering survivin and PDEF as interconnected biomarkers and targets.

DESCRIPTION (provided by applicant): The goal of this R03 pilot project is to demonstrate a proof of concept for an innovative combination treatment regimen designed to target pancreatic cancer with K-ras mutations and aberrant expression of one or more antiapoptotic proteins. K-ras oncogenic mutations and aberrant expression of major antiapoptotic proteins (e.g. survivin, Mcl-1, XIAP, cIAP2) in pancreatic cancer heavily contribute to pancreatic cancer development and aggressiveness (treatment resistance, metastasis, and relapse). Gain-of-K-ras-function mutations is observed in >90% of pancreatic cancer patients. Genetic silencing of mutated K-ras induces apoptosis and inhibits pancreatic cancer cell growth, invasiveness, malignant tumor formation, and xenograft tumor growth. However, there are no effective targeted therapies available for pancreatic cancer K-ras mutations. Using a novel screening approach with K-ras mutant cells versus normal cells, fifteen chemical constituents from the medicinal plant Amoora rohituka were identified, and over 50 derivatives were generated using semi-synthetic approaches from the 15 hits. These compounds were then rescreened using K-ras mutant cells versus normal cells. AMR-Me and AMR-MeOAc were identified as the most potent compounds selectively against the K-ras mutant cells. Our previous studies indicated that AMR-Me targets the K-ras pathway, and that 3 mg/kg daily for 28-day treatment of mice shows no clear toxicity, while it extends leukemia mouse survival. We plan to combine AMR-MeOAc (best selectivity) with our novel compound, FL118, which selectively inhibits survivin, Mcl-1, XIAP, and cIAP2, for testing this novel combinational-targeted treatment regimen. It has previously been shown that combination of K-ras silencing with gemcitabine dramatically reduces tumor volumes in mice compared with either single agent alone. Therefore, we hypothesize that inhibition of both mutated K-ras and the major antiapoptotic proteins with the novel agents AMR-MeOAc and FL118 would lead to a strikingly enhanced induction of apoptosis and inhibition of pancreatic cancer cell and tumor growth than the inhibition from either agent alone. The following three specific aims are proposed in this project. Aim 1: Determine the efficacy of AMR-MeOAc in the presence or absence of low dose FL118 on pancreatic cancer cell growth, apoptosis, and modulation of proteins in the relevant signaling pathways. Aim 2: Determine the efficacy of AMR-MeOAc in the presence or absence of low dose FL118 using human pancreatic cancer cell line-derived xenograft models. Aim 3: Determine the efficacy of AMR-MeOAc in the presence or absence of low dose FL118 against xenografts directly derived from patient pancreatic cancer tissues. Pancreatic cancer with K-ras gain-of-function mutations and aberrant expression of one or more antiapoptotic proteins (survivin, Mcl-1, XIAP, cIAP2) is hard to treat. This project may develop a novel and targeted combination strategy to effectively control this challenging and difficult-to-treat cancer.

DESCRIPTION (provided by applicant): In the past decade, while the overall cancer incidence rate tends to declining, pancreatic cancer remains the most aggressive human cancer with a very poor survival rate (3-6% for 5-year survival) and no improvement in outcomes. For example, in the United States, the estimated new cases of pancreatic cancer and deaths from this disease have grown over the past six years (2008: 37,680 new cases and 34,290 deaths; 2013: 45,220 new cases and 38,460 deaths). The challenge of this disease is basically due to the striking inherent resistance of pancreatic cancer to treatment (chemotherapy, radiation). The goal of this R21 exploratory project is to explore the mechanistic novelty and anti-pancreatic cancer efficacy of a novel anticancer agent (designated FL118) that is designed to overcome a common mechanism of treatment resistance resulting from the increased expression of one or more antiapoptotic proteins (survivin, Mcl-1, XIAP, cIAP2) from the inhibitor of apoptosis (IAP) and Bcl-2 families. The other major mechanism of treatment resistance of pancreatic cancer is the loss of functional p53 (mutated or null). In this regard, FL118 selectively inhibits the expression of survivin, XIAP, cIAP2 and Mcl-1 in a p53 status (wild type, mutant or null) independent manner. Consistently, we have reported that many non-pancreatic cancers are sensitive to FL118, independently of their p53 status. We hypothesize that although FL118 has structural similarity to camptothecin, FL118 is a novel anticancer agent with mechanisms of action distinct from other camptothecin analogs such as topotecan, and FL118 is superior for treatment of pancreatic cancer when compared to current FDA approved camptothecin analogs (e.g. topotecan) or other anticancer agents (gemcitabine). The hypothesis will be tested in three Specific Aims: Aim 1: Characterize FL118 target selectivity using topotecan as a comparative control. We will use multiple approaches to determine FL118 target selectivity. This includes FL118 and topotecan in response to treatment resistant factors of Top1 mutations; expression of survivin, Mcl-1, XIAP and/or cIAP2; p53 mutant or p53 null; expression of ABCG2/BCRP or ABCC4/MRP4; and induction of apoptosis. Aim 2: Determine FL118 efficacy in mouse models of treatment resistant human pancreatic cancer cell-established xenografts. We will use both topotecan and gemcitabine (the most commonly used single regimen drug for pancreatic cancer treatment in clinical practice) for efficacy comparative studies. Aim 3: Determine FL118 efficacy against xenografts directly derived from pancreatic cancer patients. Both topotecan and gemcitabine will also be used as comparative controls for efficacy studies in this system. Same as in Aim 2 above, both subcutaneous and orthotopic xenograft tumor models will be used in these studies. We expect that this project would not only provide new hopes and perspectives for effective management of pancreatic cancer, but may also open new research strategies or directions to conquer this deadly disease.