Citations

Abstract Breast cancer is the most common form of cancer diagnosed and the second leading cause of cancer death among women in the United States. Cancer metastases are the major cause of morbidity and mortality among breast cancer patients. The central importance of the HER2/RAS signaling pathway has been well established in promoting tumor growth, invasion and metastasis of human breast cancer. Even though oncogenic K-RAS mutations are rare in breast cancer, activation of the growth-promoting ERBB/RAS pathway has been consistently documented in high-grade breast tumors. As such, novel approaches to inhibit activated HER2/RAS signals constitute important measures to block tumor growth and metastasis in mammary tumors. In this study, instead of targeting an upstream signaling component such as HER2/EGFR/RAS, we targeted the most downstream signaling module identified in the ERBB/RAS pathway – the SIAH proteolytic machinery. SIAH is an evolutionarily conserved RING E3 ligase that is a critical “gatekeeper” required for RAS signal transduction in human cancer cells. SIAH is specifically expressed in tumor cells in 120 human breast cancer patients examined so far. The increased SIAH expression is correlated with increased grades and aggressiveness of human breast cancer. We asked whether inhibiting the gatekeeper function of SIAH would be effective in blocking mammary tumorigenesis and metastasis in human breast cancer. Our results indicated that SIAH2-deficiency successfully abolished tumor growth of three breast cancer cell lines (MDA-MB-231, MDA-MB-435 and MDA-MB-468) in soft agar assays as well as in athymic nude mice. Importantly, by inhibiting SIAH2 function in highly aggressive human breast cancer cells, we are able to completely block tumorigenesis and metastasis of two highly invasive and metastatic human breast cancer cell lines (MDA-MB-231 and MDA-MB-435). These results suggest that SIAH2 may be an attractive and new drug target for novel breast cancer therapy. Developing anti-SIAH molecules will aid in expanding our arsenal of effective anticancer therapies. By attacking the growth-promoting HER2/EGFR/RAS pathway at multiple signaling modules simultaneously – a multi-pronged synergistic inhibition at upstream (HER2/EGFR membrane receptors), midstream (RAS/RAF/MEK/mTOR) and downstream (SIAH E3 ligase) signaling modules in the HER2/EGFR/RAS pathway in parallel, we may be in a position to halt the genesis, progression and metastasis of human breast cancer. Thus, SIAH-dependent proteolysis may be an Achilles heel for breast cancer. SIAH inhibition may represent an innovative and logical way to inhibit HER2/EGFR/K-RAS activation, alleviate tumor burdens, halt cancer metastasis, and improve the efficacy for the future treatment of breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1659. doi:10.1158/1538-7445.AM2011-1659

Abstract Hyperactive K-RAS signaling is a major menace that drives aggressive tumor growth and metastasis in human cancer. Currently, there are no effective ways to treat human cancers that have oncogenic K-RAS mutations that confer drug resistance, aggressive tumor growth, systemic metastasis, and poor clinical outcome. Therefore, finding novel approaches and new drug targets to inhibit oncogenic K-RAS is an urgent goal and the major challenge in cancer therapy and treatment. Instead of targeting an upstream signaling module such as EGFR/HER2/KRAS/B-RAF/MEK/MAPK/AKT/mT0R, we targeted the most downstream signaling module in the EGFR/HER2/K-RAS pathway called the SIAH-dependent proteolytic machinery. SIAHs are the human homologs of seven-in-absentia (SINA), an evolutionarily conserved RING E3 ligase, an essential downstream signaling module, and a critical gatekeeper required for proper ERBB/RAS/RAF signal transduction. Guided by the insights and principles learned from Drosophila RAS signaling pathway, we conducted preclinical studies to dissect SIAH function in the context of ERBB/K-RAS-mediated tumorigenesis and metastasis in human cancer cells and tumor specimens. We found that: 1) SIAH is a novel biomarker for human cancer, i.e., SIAH specifically decorates proliferating tumor cells (not stromal or immune cells in the tumor microenvironment). SIAH expression is progressively and markedly upregulated as human cancer progresses to the advanced stages in human pancreatic, lung, breast, and prostate cancers; and 2) inhibiting SIAH function is highly effective to abolish tumorigenesis and metastasis in multiple of the most aggressive human cancer cell lines known in the literature that include pancreatic cancer cells (MiaPaCa and Panc-1), lung cancer cells (A549, H727, and UMC11), invasive breast cancer cells (MDA-MB-231, MDA-MB-468, and MDA-MB-435), colorectal cancer cells (SW620 and HCT116) and hormonal-refractory prostate cancer cells (PC-3 and DU-145) in our preclinical studies. These findings demonstrate that SIAH is an attractive and logical new therapeutic target for novel anti-K-RAS and anticancer therapy in human cancer. Through our work, SIAH has emerged as a new and effective drug target against oncogenic K-RAS activation in human cancer cells. Using anti-SIAH molecules to block K-RAS signaling in human cancer is an excellent example of science going from the bench (basic research in fruit flies) to the bedside (preclinical studies and ultimately clinical trials). As a highly evolutionarily conserved E3 ligase and the most downstream gatekeeper of EGFR/HER2/K-RAS/B-RAF signaling pathway, SIAH is uniquely and logically positioned to become a next-generation anti-K-RAS drug target. Our preclinical studies have demonstrated that SIAH-dependent proteolysis is an Achilles' heel for human cancer cells. Albeit at an early preclinical stage, knowledge gained from our study has great promise that has generated many excitements with immediate translational values. Anti-SIAH-based small molecule inhibitors may aid in expanding our arsenal of novel anticancer therapies. By attacking the oncogenic ERBB/K-RAS/B-RAF pathway using multipronged synergistic inhibitions at upstream (EGFR/HER2 membrane receptors), midstream (K-RAS/B-RAF/MEK/mTOR), and downstream (SIAH E3 ligase) signaling modules in parallel, we will be in a great position to halt the genesis, progression, and metastasis of the most aggressive and the deadliest forms of human cancers. If successful, we hope to translate our findings to the cancer clinics to treat many cancer patients with metastatic diseases in the near future. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr B14.

Abstract We performed a meta-analysis of 3 genome-wide association studies to identify additional common variants influencing chronic lymphocytic leukemia (CLL) risk. The discovery phase was composed of genome-wide association study data from 1121 cases and 3745 controls. Replication analysis was performed in 861 cases and 2033 controls. We identified a novel CLL risk locus at 6p21.33 (rs210142; intronic to the BAK1 gene, BCL2 antagonist killer 1; P = 9.47 × 10−16). A strong relationship between risk genotype and reduced BAK1 expression was shown in lymphoblastoid cell lines. This finding provides additional support for polygenic inheritance to CLL and provides further insight into the biologic basis of disease development.

Abstract Background: Colorectal cancer (CRC) is the third most common incident cancer among women in the United States. Alcohol use has been proposed as a CRC risk factor, but existing observational data remain inconsistent. To date, relatively few studies have examined associations between alcohol use and CRC risk based on molecularly-defined subtypes. Aim: To evaluate associations between alcohol use and incident CRC overall, as well as by molecularly-defined subtypes including microsatellite instability (MSI), CpG island methylator phenotype (CIMP) and BRAF mutation status in the prospective, population-based, Iowa Women's Health Study (IWHS). Methods: The IWHS recruited 41,836 randomly selected Iowa women, ages 55–69 years at enrollment, in 1986. Women with prevalent cancers or no follow-up were excluded, leaving 38,001 eligible for this study. Alcohol use was obtained from a self-administered food frequency questionnaire at study baseline. Incident CRCs were identified through annual linkage with the State Health Registry of Iowa. Archived, paraffin-embedded tissue specimens were recently requested for incident CRC cases diagnosed through December 31, 2002. In the present study, useable tissue specimens were obtained and molecularly characterized for 563/1,255 cases (45%), whose baseline age, body mass index, physical activity level, total energy intake and alcohol use were similar to non-retrieved cases (p > 0.05 for each comparison). Alcohol use was categorized as never (n=21,464), < 3.4 g/day (n=8,313) and > 3.4 g/day (n=8,224), based on the median split among users. Molecularly-defined CRC subtypes were categorized as MSI-high (MSIH; n=148), MSI-low or microsatellite stable (MSI-L/MSS; n=400); CIMP-positive (n=167) or CIMP-negative (n=368); and BRAF-mutation (n=154) or BRAF-wildtype (n=391). Relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated for alcohol use compared to never drinkers, using multivariable Cox regression models adjusted for body mass index, waist-to-hip ratio, smoking status, physical activity level, exogenous estrogen use, and daily intakes of total energy, total fat, red meat, sucrose, calcium, folate, methionine and vitamin E. Results: There was no statistically significant association between alcohol use and overall CRC risk (RR=1.00; 95% CI = 0.86–1.15 for < 3.4 g/day versus none; RR=1.06; 95% CI=0.91–1.24 for >3.4 g/day versus none). Further, there were no associations with alcohol use for specific, molecularly-defined CRC subtypes (RRs shown for > 3.4 g/day versus none): MSI-H (RR=1.07; 95% CI=0.70–1.64); MSI-L or MSS (RR=1.12; 95% CI=0.85–1.47); CIMP-positive (RR=0.97; 95% CI=0.64–1.47); CIMP-negative (RR=1.13; 95% CI=0.85–1.50); BRAF-mutation (RR=0.94; 95% CI=0.61–1.45); and BRAF-wildtype (RR=1.20; 95% CI=0.91–1.57). Conclusion: In this cohort of older women, alcohol use did not appear to be a risk factor for incident CRC, overall or by the defined molecular subtypes. Citation Information: Cancer Prev Res 2010;3(1 Suppl):A115.

Abstract The central importance of the ERBB/RAS signal transduction cascade has been well established in human cancer. As such, novel approaches to counteract activated ERBB/RAS signals constitute important measures to reverse tumorigenesis and metastasis in human cancers. Instead of targeting an upstream signaling module such as ERBB/RAS/MEK/MAPK/AKT/mTOR, we targeted the most downstream signaling module in the ERBB/RAS pathway called the SIAH-dependent proteolytic machinery. SIAHs are the human homologs of Seven-In-Absentia (SINA), an evolutionarily conserved RING E3 ligase, an essential downstream signaling module and a critical “gatekeeper” required for proper Drosophila RAS signal transduction. Guided by the insights and principles learned from Drosophila RAS signaling pathway, we conducted preclinical studies to examine SIAH function in the context of RAS-mediated tumorigenesis and metastasis in human cancer cells.We found that (1) SIAH is a novel biomarker for human cancer, i.e. it specifically decorates proliferating tumor cells (not stromal cells in the tumor microenvironment). SIAH expression is progressively and markedly upregulated as human cancer progresses to the advanced stages in human pancreatic, lung, breast and prostate cancers; and (2) inhibiting the proteolytic function of SIAH is highly effective to abolish tumorigenesis and metastasis in eight of the most aggressive human cancer cell lines known in the literature that include pancreatic cancer cells (MiaPaCa and Panc-1), lung cancer cells (A549), invasive breast cancer cells (MDA-MB-231, MDA-MB-468 and MDA-MB-435) and hormonal-refractory prostate cancer cells (PC-3 and DU-145) in soft agar as well as in athymic nude mice. These findings suggest that SIAH may be an attractive new therapeutic target for novel anti-RAS and anti-cancer therapy in human cancer. As a highly evolutionarily conserved E3 ligase and consistent with its “gatekeeper” function identified in the ERBB/RAS signaling pathway, SIAH is well positioned to become a next-generation and potent anticancer drug target to block the tumor-promoting RAS pathway and to treat the most aggressive types of human cancers. “Using anti-SIAH molecules to block active RAS signaling in human cancer” may be another example of “from the bench [basic science from fruitflies (model organism) to human cancers] to the bedside story [translational medicine in the near future]”. Anti-SIAH-based anticancer strategy may aid in expanding our arsenal of novel anticancer therapies. By attacking the oncogenic ERBB/RAS pathway using multi-pronged synergistic inhibitions at upstream (EGFR/HER2 membrane receptors), midstream (RAS/RAF/MEK/mTOR) and downstream (SIAH E3 ligase) signaling modules in parallel, we may be in a great position to halt the genesis, progression and metastasis of the most aggressive and lethal types of human cancers. If successful, we hope to translate our findings to the cancer clinics to treat many cancer patients with metastatic diseases in the future. Citation Information: Cancer Res 2009;69(23 Suppl):A1.