Citations

Abstract Purpose: To assess the role of insulin-like growth factor binding protein 5 (IGFBP-5) as a marker of relapse and survival in breast cancer tumors. Experimental Design: Targeted regulation of IGFBP-5 was identified in MCF-7 cells resistant (MCF-7R4) to the IGF-1R/InsR inhibitor, BMS-536924 and examined by comparative microarray analysis, western and ELISA. Protein expression of IGFBP-5 was measured by immunohistochemistry in a cohort of 84 breast cancer patients to examine correlative associations with invasive tumor fraction and overall survival (OS). The expression ratio of IGFBP-5/IGFBP-4 (BPR) was determined in multiple breast tumor cohorts for univariate analysis. Results: IGFBP-5 was markedly upregulated and highly localized to the membrane in MCF-7R4 resistant cells. When compared to pathologically normal reduction mammoplasty tissue, IGFBP-5 expression levels were upregulated in both invasive and histologically normal adjacent breast cancer tissue. In an independent cohort of breast cancer patients, IGFBP-5 protein levels correlated directly with invasion and OS. In univariate and multivariate modeling, metastasis-free survival, recurrence free survival (RFS) and OS were significantly associated with high IGFBP-5 expression. Prognostic power of IGFBP-5 was further increased with the addition of IGFBP-4 and tumors were ranked based upon IGFBP-5/IGFBP-4 expression ratio (BPR). Multiple breast cancer cohorts confirm that BPR (high vs. low) was a strong predictor of RFS and OS. Conclusion: IGFBP-5 expression is a marker of poor outcome in breast cancer patients. An IGFBP-5/IGFBP-4 expression ratio may serve as a surrogate biomarker of IGF pathway activation and predict sensitivity to IGF-1R-targeted therapies. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-11-11.

Abstract We have recently showed that the immunophilin FKBP5 (also known as FKBP5) as a scaffolding protein that can enhance PHLPP-AKT interaction and facilitate PHLPP-mediated dephosphorylation of AKT-Ser473, negatively regulating AKT activation in vitro. Therefore, FKBP5 might function as a tumor suppressor and levels of FKBP5 would affect cell response to chemotherapy. In the current study, we took a step forward by using pancreatic caner xenograft mice model to show that FKBP5−/− promotes tumor growth and renders resistance to gemcitabine and addition of AKT inhibitors have more significant sensitization effect on FKBP5−/− mice to gemcitabine treatment. The combination of triciribine and gemcitabine resulted in cooperative inhibition of pancreatic cancer cell proliferation and the growth of xenografts in vivo without increasing toxicity, as well as cooperative inhibition of AKT signaling pathways at concentrations that were ineffective as individual agents. These results provide evidence for future clinical studies designed to tailor the therapy based on the biomarker. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C15.

Abstract Purpose: To improve the significance of insulin-like growth factor–binding protein 5 (IGFBP-5) as a prognostic and potentially predictive marker in patients with breast cancer. Experimental Design: Increased IGFBP-5 expression was identified in MCF-7 cells resistant (MCF-7R4) to the IGF-1R/insulin receptor (InsR) inhibitor BMS-536924 and its role examined by targeted knockdown and overexpression in multiple experimental models. Protein expression of IGFBP-5 was measured by immunohistochemistry in a cohort of 76 patients with breast cancer to examine correlative associations with invasive tumor fraction and outcome. The use of a combined IGFBP-5/IGFBP-4 (BPR) expression ratio was applied to predict anti-IGF-1R/InsR response in a panel of breast cancer lines and outcome in multiple breast tumor cohorts. Results: IGFBP-5 knockdown decreased BMS-536924 resistance in MCF-7R4 cells, whereas IGFBP-5 overexpression in MCF-7 cells conferred resistance. When compared with pathologically normal reduction mammoplasty tissue, IGFBP-5 expression levels were upregulated in both invasive and histologically normal adjacent breast cancer tissue. In both univariate and multivariate modeling, metastasis-free survival, recurrence free survival (RFS), and overall survival (OS) were significantly associated with high IGFBP-5 expression. Prognostic power of IGFBP-5 was further increased with the addition of IGFBP-4 where tumors were ranked based upon IGFBP-5/IGFBP-4 expression ratio (BPR). Multiple breast cancer cohorts confirm that BPR (high vs. low) was a strong predictor of RFS and OS. Conclusion: IGFBP-5 expression is a marker of poor outcome in patients with breast cancer. An IGFBP-5/IGFBP-4 expression ratio may serve as a surrogate biomarker of IGF pathway activation and predict sensitivity to anti-IGF-1R targeting. Clin Cancer Res; 18(6); 1808–17. ©2012 AACR.

AbstractSik-similar protein (Sik-SP), a small nucleolar ribonucleoprotein, has been shown to be primarily involved in ribosome biogenesis. However, its role in the hormone-directed nuclear receptor signaling is largely unknown. Here, we provide novel evidence that Sik-SP is required for appropriate regulation of estrogen receptor (ER)α-mediated estradiol-17β (E2)-dependent uterine physiologic responses in mice. Studies by Western blotting using the newly developed antibodies for Sik-SP showed that this protein is up-regulated in both the ovariectomized wild-type and ERα null uteri by E2. Immunohistochemical analyses in uterine sections showed that this protein is induced in the epithelial and stromal cells. Coimmunoprecipitation studies revealed that E2 directs molecular interaction between Sik-SP and ERα. Furthermore, gel-mobility shift and chromatin immunoprecipitation analyses provided evidence that Sik-SP is recruited with ERα to estrogen-responsive uterine gene promoters. Overexpression of Sik-SP in vitro demonstrated a role for Sik-SP in cellular growth and viability. In a primary uterine epithelial-stromal coculture system, E2 exhibited early induction of Sik-SP in both the epithelial and stromal cells. Interestingly, suppression of Sik-SP in this coculture model, for the stromal but not epithelial cells, caused perturbation of E2-dependent proliferation in the epithelial cell layer. Similarly, in vivo uterine suppression of Sik-SP also caused inhibition of epithelial cell proliferation and aberrant prolongation of water imbibition in the late phase by E2. Finally, studies showed that Sik-SP is physiologically important during the onset of implantation by E2. In conclusion, Sik-SP, an early E2-responsive nucleolar protein, is necessary to induce E2-dependent ERα-mediated appropriate physiologic responses in the uterus.

Abstract Insulin-like growth factor (IGF) signaling has been implicated in the resistance to hormonal therapy in breast cancer. Using a model of postmenopausal, estrogen-dependent breast cancer, we investigated the antitumor effects of the dual IGF-1R/InsR tyrosine kinase inhibitor BMS-754807 alone and in combination with letrozole or tamoxifen. BMS-754807 exhibited antiproliferative effects in vitro that synergized strongly in combination with letrozole or 4-hydroxytamoxifen and fulvestrant. Similarly, combined treatment of BMS-754807 with either tamoxifen or letrozole in vivo elicited tumor regressions not achieved by single-agent therapy. Notably, hormonal therapy enhanced the inhibition of IGF-1R/InsR without major side effects in animals. Microarray expression analysis revealed downregulation of cell-cycle control and survival pathways and upregulation of erbB in response to BMS-754807 plus hormonal therapy, particularly tamoxifen. Overall, these results offer a preclinical proof-of-concept for BMS-754807 as an antitumor agent in combination with hormonal therapies in hormone-sensitive breast cancer. Cooperative cell-cycle arrest, decreased proliferation, and enhanced promotion of apoptosis may contribute to antitumor effects to be gauged in future clinical investigations justified by our findings. Cancer Res; 71(24); 7597–607. ©2011 AACR.

Abstract Background: The single-nucleotide polymorphism (SNP) 5p12-rs10941679 has been found to be associated with risk of breast cancer, particularly estrogen receptor (ER)-positive disease. We aimed to further explore this association overall, and by tumor histopathology, in the Breast Cancer Association Consortium. Methods: Data were combined from 37 studies, including 40,972 invasive cases, 1,398 cases of ductal carcinoma in situ (DCIS), and 46,334 controls, all of white European ancestry, as well as 3,007 invasive cases and 2,337 controls of Asian ancestry. Associations overall and by tumor invasiveness and histopathology were assessed using logistic regression. Results: For white Europeans, the per-allele OR associated with 5p12-rs10941679 was 1.11 (95% CI = 1.08–1.14, P = 7 × 10−18) for invasive breast cancer and 1.10 (95% CI = 1.01–1.21, P = 0.03) for DCIS. For Asian women, the estimated OR for invasive disease was similar (OR = 1.07, 95%CI = 0.99–1.15, P = 0.09). Further analyses suggested that the association in white Europeans was largely limited to progesterone receptor (PR)-positive disease (per-allele OR = 1.16, 95% CI = 1.12–1.20, P = 1 × 10−18 vs. OR = 1.03, 95% CI = 0.99–1.07, P = 0.2 for PR-negative disease; Pheterogeneity = 2 × 10−7); heterogeneity by ER status was not observed (P = 0.2) once PR status was accounted for. The association was also stronger for lower grade tumors [per-allele OR (95% CI) = 1.20 (1.14–1.25), 1.13 (1.09–1.16), and 1.04 (0.99–1.08) for grade 1, 2, and 3/4, respectively; Ptrend = 5 × 10−7]. Conclusion: 5p12 is a breast cancer susceptibility locus for PR-positive, lower grade breast cancer. Impact: Multicenter fine-mapping studies of this region are needed as a first step to identifying the causal variant or variants. Cancer Epidemiol Biomarkers Prev; 20(10); 2222–31. ©2011 AACR.

Abstract DNA topoisomerase IIα (Topo IIα) is a critical target for cancer therapy and its protein expression, however, is frequently depleted by its inhibitors and strategies to maintain Topo IIα expression and thereby to sustain the Topo II drug sensitivity are still lacking. Here we show that p38γ MAPK is specifically activated by Topo II inhibitors and activated p38γ in turn phosphorylates Topo IIα, leading to increased Topo IIα protein expression through attenuating its proteasome-dependent degradation. The sensitivity of a panel of human breast cancer cell lines to Topo II inhibitors was found not to correlate with the intrinsic but with inducible Topo IIα protein expression and with endogenous protein expression of p38γ MAPK that is specifically phosphorylated in response to Topo II toxins. p38γ activation and inhibition alone were shown to increase and decrease Topo IIα expression and Topo drug toxicities. Mechanistically, p38γ MAPK phosphorylates Topo IIα at Ser 1524, leading to a decreased proteasome-dependent Topo IIα degradation. These results reveal a novel mechanism by which p38γ MAPK specifically confers Topo II drug toxicity in breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 317.

Abstract Background Radiation therapy is used to treat half of the all cancer patients. Response to radiation therapy varies widely, in terms of both response and toxicity related events. Previous studies suggested almost 80% of the variation in normal tissue response to radiation treatment was likely to be due to genetic factors. Therefore, we performed a genome-wide association study (GWAS) to identify biomarkers that might help predict radiation response using a the “Human Variation Panel” lymphoblastoid cell lines (LCLs) that consists 287 ethnically defined cell lines. Method Basal gene expression level, 1.3 million genome-wide SNP data were obtained for 287 human LCLs using Affymetrix U133 plus 2.0 GeneChip, Illumina HumanHap 550K, 510S BeadChips and Affymetix SNP Array 6.0. Radiation cytotoxicity assay was also performed to obtain the area under radiation dose response curve (AUC), a summary measure for cytotoxicity for the same cell lines. Functional validation of candidate genes, selected based on the integrated analysis of SNP, expression and AUC data, was performed in multiple cancer cell lines using specific siRNAs followed by MTS and colony formation assays. Results 27 loci, containing at least 2 SNPs of p values <10−4 within 50kb were associated with radiation AUC. 270 expression probe sets were associated with radiation AUC (p< 10−3). The integrated analysis of 27 loci, 54,000 basal expression probe sets and radiation AUC identified 50 unique SNPs associated with AUC were also associated with gene expression of 39 unique annotated genes. In addition, these 39 genes were associated with radiation AUC with p values <10−3. Based on the GWAS and integrated analysis of SNP, expression array and radiation AUC data, 22 genes were selected for functional validation studies using siRNA knock down followed by MTS and colony formation assays in multiple tumor cell lines. C13orf34 (Bora), MAD2L1, PLK4, TPD52 significantly altered the radiation sensitivity in at least 2 cancer cell lines for both MTS and colony formation assays (p<0.05). Knock down of DEPDC1B, a gene containing 2 SNPs at the 3′-end that was significantly related with Bora gene expression level (p<10−4) significantly desensitized cancer cells to radiation treatment. Both microarray data and QRT-PCR analysis indicated that expression levels for those two genes were significantly correlated. Conclusion Our results using the lymphoblastoid cell lines might help identify novel biomarkers that contribute to variation in response to radiation therapy and help understand the mechanisms underlying the association. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3602.