PD01-06: Endoxifen Exhibits Potent Anti-Tumor Activity and Regulates Different Genes Than Tamoxifen in an Aromatase Expressing MCF7 Model Resistant to Letrozole

Background: First in human studies of Z-endoxifen hydrochloride (E), the active metabolite of tamoxifen (T), are underway in metastatic breast cancer (BC). Previous data have demonstrated the superiority of aromatase inhibitors (AI's) over T in estrogen receptor (ER) + BC. Using an in vivo aromatase expressing model (MCF7/AC1), we compared the antitumor activity of E with T and Letrozole (L), as well as the antitumor activity and global gene expression changes of E with T in an L-resistant model.

Methods: MCF7/AC1 tumors were stimulated with androstenedione. Once tumor size reached 300 mm3, mice (30/group) were randomly assigned to one of five treatment groups: control (daily, po), T (500 μg/day, sc), endoxifen 25 mg/kg/day p.o.(LDE) endoxifen 75 mg/kg/day p.o. (HDE) or letrozole, 10 μg/day s.c for 4 weeks. Tumors were harvested from control, T, and E groups while the L group continued treatment until the development of resistance defined as an increase in tumor volume of at least 300% from day 1. Mice with L-resistant tumors were randomly assigned to T (n=4) or E (n=5) for 4 weeks and then sacrificed. Gene expression in L-resistant tumors was quantified using Affymetrix U133+2 and changes in gene expression profiles [comparing T and E with L-resistant (n=3)] were analyzed. Genes identified as significantly different were confirmed by real-time RT-PCR assays.

Results: At the 4 week time point, both doses of E and L resulted in greater anti-tumor activity than control (Wilcoxon rank sum test: all p < 0.0001); however, tumor burden did not differ between T and control (p=0.095). HDE resulted in significantly less tumor burden than T (p=0.002) but was similar to L. In mice that continued on L, resistance developed at 24 weeks in 9/25 mice. These mice were randomly assigned to either T (n=4) or E (n=5) for 4 weeks. Tumor volume (expressed as a% of its size prior to randomization) was significantly different comparing E (73.3%; range: 69.3 to 80.75%) versus T (148.39%; range: 114.07 to 165.99%) (Wilcoxon rank sum test p=0.016). Compared to control, microarray studies identified 1518 unique probe sets regulated by E (p<0.001) compared to 441 for T including estrogen-regulated genes such as progesterone receptor (PGR) and amphiregulin (AREG) that were significantly down-regulated in the E group [PGR (−6.2 fold, p=0.000008) and AREG (−3.2 fold, p=.0006) but unchanged or up-regulated in the T group (PGR unchanged and AREG +9.2 fold p=0.00002). These findings were confirmed by RT-PCR.

Conclusions: Using the MCF7/AC1 model previously used to show the superiority of AI's over T, HDE demonstrated similar antitumor activity to L and was superior to T. In cells resistant to L, E was superior to T and gene expression changes demonstrate that E down-regulates while T activates estrogen regulated genes. These findings support the ongoing development of E for the treatment of ER+ BC.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD01-06.

P2-11-11: IGFBP Ratio Confers Resistance to IGF Targeting and Correlates with Increased Invasion and Poor Outcome in Breast Tumors

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.

Increment of 30-min post-challenge plasma glucose is associated with urine albumin excretion in men with normal glucose regulation

AIMS

The overwhelming majority of subjects with normal glucose regulation have the highest plasma glucose concentration at 30 minutes during oral glucose tolerance. We aimed to examine the association between increment of 30-min post-challenge glucose and albuminuria in participants with normal glucose regulation.

METHODS

A population-based cross-sectional study was conducted in six communities in Shanghai between 2007 and 2008. A total of 3508 subjects with normal glucose regulation had complete data and were enrolled into the analysis. Among the selected subjects, only 1525 individuals (581 men, 944 women) were examined for their serum insulin levels. We assessed post-challenge blood glucose and insulin at 0, 30 and 120 min, urinary albumin and creatinine. The 30-min post-challenge glucose increment (Δ) was calculated as 30-min post-challenge glucose minus fasting plasma glucose, and albumin/creatinine ratio was used to reflect urinary albumin excretion.

RESULTS

Multivariable logistic regression analysis revealed that the Δ30-min post-challenge glucose was independently associated with increased albumin/creatinine ratio in men with normal glucose regulation (OR = 1.08, P = 0.025), but not in women. Furthermore, multivariable linear regression analysis revealed that early-phase glucose disposition index was the main factor responsible for Δ30-min post-challenge glucose and explained 14-20% of the variance of Δ30-min post-challenge glucose in the two subgroups (P < 0.05). Notably, men had higher Δ30-min post-challenge glucose and lower early-phase glucose disposition index than women (all P < 0.001).

CONCLUSIONS

The 30-min post-challenge plasma glucose increment is associated with urine albumin excretion in men with normal glucose regulation.

Evidence for two independent associations with type 1 diabetes at the 12q13 locus

Genome-wide association studies have identified associations between type 1 diabetes and single nucleotide polymorphisms (SNPs) at chromosome 12q13, surrounding the gene ERBB3. Our objective was to fine map this region to further localize causative variants. Re-sequencing identified more than 100 putative SNPs in an 80 kb region at 12q13. By genotyping 42 SNPs, spanning approximately 214 kb, in 382 affected sibling pair type 1 diabetes families, we were able to genotype or tag 67 common SNPs (MAF ≥ 0.05) identified from HapMap CEU data and CEU data from the 1000 Genomes Project, plus additional rare coding variants identified from our re-sequencing efforts. Fifteen SNPs provided nominal evidence for association (P≤ 0.05) with type 1 diabetes. The most significant associations were observed with rs2271189 (P = 4.22×10⁻⁵), located in exon 27 of the ERBB3 gene, and an intergenic SNP rs11171747 (P= 1.70×10⁻⁴). Follow-up genotyping of these SNPs in 2 740 multiplex type 1 diabetes families validated these findings.

After analyzing variants spanning more than 200 kb, we have replicated associations from previous GWAS and provide evidence for novel associations with type 1 diabetes. The associations across this region could be entirely accounted for by two common SNPs, rs2271189 and rs11171747.

Do We Have the Right Prognostic Index for Diffuse Large B Cell Lymphoma (DLBCL) in the Era of Rituximab?

Introduction:

Whilst the addition of rituximab, a humanized monoclonal antibody to standard CHOP chemotherapy (R-CHOP) has improved the outcomes of DLBCL, the validity of the previously identified prognostic index based on clinical parameters is questioned. It is conceivable that prognostic model may alter with introduction of new therapeutics with differing efficacy and mechanisms of action.

Methods:

We conducted a retrospective analysis comparing the relevance of International Prognostic Index (IPI), Age-adjusted IPI and Revised International Prognostic Index (R-IPI) in 320 consecutive patients with DLBCL from 2003–2008 treated with R-CHOP chemotherapy with curative intent. We evaluated the prognostic factors determinant of survival in our group of patients.

Results:

Patients were followed up for a median of 2.70 years. IPI was only able to stratify patients into 3 main risk groups instead of 4. In addition, among patients <60, aa-IPI no longer seem a robust prognostic model. We showed that R-IPI was able to separate patients into 3 different prognostic groups and perhaps most relevant in the era of chemo-immunotherapy. Significant prognostic factors identified in multivariate analysis were performance status (P=0.004) and bone marrow involvement (P=0.026).

Conclusion:

The most robust prognostic index for patients with DLBCL in the era of rituximab remains uncertain. Incorporation of molecular markers into clinical parameters should be evaluated, a study we are embarking on.

Validation of the AJCC staging system (7th edition) in Asian patients with localized prostate cancer undergoing radical radiotherapy

112

Background: The epidemiology of prostate cancer (PCa) varies widely internationally. Although prostate cancer is usually regarded as uncommon in Asia, dramatic rises in recent years have resulted in it being ranking third by incidence in Singapore. Conventional prognostic parameters derived from Western populations have been integrated into systems such as the new AJCC seventh edition staging system, the validity of which is unclear in Asia. We thus sought to validate its performance, alongside other prognostic factors in a large Asian series of radiotherapy patients.

Methods: A retrospective review of 404 consecutive Singaporean patients receiving radical radiotherapy between 1997 and 2005 at the National Cancer Centre was performed. The primary outcome was biochemical relapse free survival (BRFS), defined by the Phoenix criteria. Prognostic risk groups were defined using AJCC seventh edition. Univariate analysis (UVA) and multivariate analysis (MVA) was performed for other putative risk factors: age, race, Gleason score, prognostic risk grouping, tumour classification, radiation delivery technique, radiotherapy dose, hormonal therapy (HT) and initial PSA.

Results: Median age was 69; median BRFS was 55 months with 71 biochemical relapses. 4 risk factors showed univariate association with BRFS: AJCC risk groups (p=0.038), T-stage (p=0.018), RT dose (p=0.025) and initial PSA value (p=0.013) with AJCC risk groups and initial PSA value remaining significant after MVA ( Table ). Harrell's c-index for AJCC risk grouping was 0.56, with no significant difference seen in outcomes between AJCC risk group II and III.

Conclusions: Our results validate the new AJCC seventh edition prostate cancer prognostic risk grouping in an Asian radiotherapy population for the first time; the actual association however is relatively weak possibly due to differences in biology, screening or epidemiology.

[Table: see text]

No significant financial relationships to disclose.

Central nervous system (CNS) relapse in diffuse large B cell lymphoma (DLBCL): pre- and post-rituximab

Central nervous system (CNS)-directed prophylactic intrathecal (IT) therapy is indicated in patients with Burkitt and acute lymphoblastic lymphoma. Its role in diffuse large B cell lymphoma (DLBCL), a heterogeneous subtype, is less well defined. While addition of rituximab to standard cyclophosphamide-hydroxydaunorubicin-oncovin-prednisone (CHOP) chemotherapy (R-CHOP) has improved the outcomes of DLBCL patients, its role in reducing CNS relapse is unclear. We aim to (1) evaluate the clinical risk factors predictive of CNS relapse, (2) the role of rituximab in influencing CNS relapse, and (3) role of intrathecal prophylaxis. Four hundred ninety-nine patients with DLBCL from 2000 to 2008 were included (CHOP 179 vs. R-CHOP 320). IT prophylaxis was administered to 82 patients based on our institution's guidelines. Baseline characteristics between CHOP- and R-CHOP-treated patients were similar. Although R-CHOP significantly increased the complete remission rate from 71% to 81% (P < 0.01), CNS relapse rates remained unchanged (R-CHOP 6% vs. CHOP 5.1%). On multivariate analysis, poor performance status (Eastern Cooperative Oncology Group >1; hazard ratio (HR) = 2.01, 95% confidence interval (CI) 1.29-3.14), failure to attain remission (non-complete response (CR) vs. CR: HR = 2.39, 95% CI = 1.03 to 5.51), testicular (HR = 6.67, 95% CI = 1.62 to 27.53), kidney (HR = 20.14, 95% CI = 5.23 to 77.46), and breast involvement (HR = 6.14, 95% CI = 1.61 to 23.37) were each independently predictive of CNS relapse. Use of IT prophylaxis did not appear to decrease CNS relapse. Median survival after CNS relapse was 3.2 months. CNS relapse, a fatal event, remains a challenge in R-CHOP-treated patients. IT prophylaxis may not be sufficient to reduce CNS relapse, and strategies including systemic agents with high CNS penetration should be evaluated in high-risk patients identified in this study.

Central nervous system (CNS) relapse in diffuse large B cell lymphoma (DLBCL): pre- and post-rituximab

Central nervous system (CNS)-directed prophylactic intrathecal (IT) therapy is indicated in patients with Burkitt and acute lymphoblastic lymphoma. Its role in diffuse large B cell lymphoma (DLBCL), a heterogeneous subtype, is less well defined. While addition of rituximab to standard cyclophosphamide-hydroxydaunorubicin-oncovin-prednisone (CHOP) chemotherapy (R-CHOP) has improved the outcomes of DLBCL patients, its role in reducing CNS relapse is unclear. We aim to (1) evaluate the clinical risk factors predictive of CNS relapse, (2) the role of rituximab in influencing CNS relapse, and (3) role of intrathecal prophylaxis. Four hundred ninety-nine patients with DLBCL from 2000 to 2008 were included (CHOP 179 vs. R-CHOP 320). IT prophylaxis was administered to 82 patients based on our institution's guidelines. Baseline characteristics between CHOP- and R-CHOP-treated patients were similar. Although R-CHOP significantly increased the complete remission rate from 71% to 81% (P < 0.01), CNS relapse rates remained unchanged (R-CHOP 6% vs. CHOP 5.1%). On multivariate analysis, poor performance status (Eastern Cooperative Oncology Group >1; hazard ratio (HR) = 2.01, 95% confidence interval (CI) 1.29-3.14), failure to attain remission (non-complete response (CR) vs. CR: HR = 2.39, 95% CI = 1.03 to 5.51), testicular (HR = 6.67, 95% CI = 1.62 to 27.53), kidney (HR = 20.14, 95% CI = 5.23 to 77.46), and breast involvement (HR = 6.14, 95% CI = 1.61 to 23.37) were each independently predictive of CNS relapse. Use of IT prophylaxis did not appear to decrease CNS relapse. Median survival after CNS relapse was 3.2 months. CNS relapse, a fatal event, remains a challenge in R-CHOP-treated patients. IT prophylaxis may not be sufficient to reduce CNS relapse, and strategies including systemic agents with high CNS penetration should be evaluated in high-risk patients identified in this study.