Abstract P1-08-31: Putative role of genetic variants of eNOS in survival and toxicity of patients given antiangiogenic therapy

Background: The development of tumor angiogensis is mainly driven by vascular endothelial growth factor (VEGF), which is strongly overexpressed in many cancers. VEGF induces the expression of the endothelial nitric oxide (NO) synthase (eNOS) and the resultant overproduction of NO may be associated with recruitment of inflammatory cells, disruption of endothelial barrier, edema and impaired drug delivery within tumors (1). Functional polymorphisms in the eNOS gene, including -786C>T and 894G>T, have been associated with impaired production of NO and higher incidence of hypertension (HT) (2), diabetic nephropathy (3) and glaucoma (4). Since suppression of VEGF-eNOS signal transduction by antiangiogenic drugs may normalize tumor vasculature by restoring interstitial fluid pressure and drug distribution in tumors, but may induce HT in patients, the purpose of this study was to examine the association between the major eNOS variants -786C>T and 894G>T with treatment outcome and risk of HT in metastatic breast cancer (MBC) patients given bevacizumab. Methods: Sixty-five MBC patients given bevacizumab as per approved indication were enrolled. Main characteristics were: mean age 49.5 years (range 29-73) at first diagnosis, 53 years (range 34-74) at metastatic progression and PS 0-1. Four subjects with HT and 1 patient with compensated cardiovascular disease were also included. First-line chemotherapy for metastatic disease was taxol plus bevacizumab. Germline DNA was extracted from peripheral blood with the Qiamp Mini Kit (Qiagen, Milano, Italy) and examined for eNOS -786C>T and 894G>T variants by Real Time PCR (Life Sciences 7900HT platform) and automatic sequencing (Life Sciences 3100 Avant). The study was approved by the local Ethics Committee. Results: Genotype frequencies are reported below (Table 1). The presence of -786TT genotype was associated with longer PFS compared with the other genotypes (median PFS 95%CI, CC/CT = 9 vs TT = 12 months, Log-rank [Mantel Cox] test p = 0.0066), but not with any grade of HT. Also the 894GT/TT was associated with longer PFS compaed with the GG homozygous wild-type genotype (median PFS 95%CI, GG = 7,5 vs GT/TT = 10 months, Log-rank [Mantel-Cox] test p = 0,0497). The incidence and severity of HT did not vary among genotypes. Conclusion: Patients bearing deficient eNOS variant did not experience higher risk or severity of HT with respect to the wild-type allele but enjoied a longer PFS.

Table 1. Genotype frequenciesSNPFrequencies%Frequencies%Frequencies%-786C>TCCCTTT 37%33.8%26.2%894G>TGGGTTT 41.5%53.8%4.6%

References

1. Goel S et al. Physiol Rev 2011;91:1071

2. Niu W, Qi Y. PLoS One 2011;6:e24266

3. Rahimi Z et al. Dis Markers 2013;34:437

4. Awadalla MS et al. Invest Ophtalmol Vis Sci 2013;54:2108.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-08-31.

Abstract P5-17-06: The deficient eNOS c.894G>T genotype is not associated with increased severity of hypertension and proteinuria in breast cancer patients receiving bevacizumab

Background. Tumor angiogenesis is a complex process involving a wide array of effector molecules and stromal cells. In tumor tissue, vasculature is structurally and functionally abnormal, causing elevated interstitial pressure and irregular perfusion. The expression of vascular endothelial growth factor (VEGF), the most important angiogenic factor, is enhanced in many tumors. VEGF may induce nitric oxide (NO) production via up-regulation of the endothelial NO synthase (eNOS, NOS3) and the resultant overproduction of NO is associated with vasodilation and edema within tumors (Goel S et al. Physiol Rev 2011;91:1071). eNOS plays an important physiologic role in maintaining blood pressure homeostasis and vascular integrity by providing constitutive release of NO in endothelial cells. Functional variants of the eNOS gene, including the single-nucleotide polymorphism rs1799983 (c.894G>T, p. Asp298Glu) at codon 298, have been associated with reduced function of eNOS and higher incidence of hypertension (HT) (Niu W, Qi Y. PLoS One 2011;6:e24266).

Purpose. Since suppression of VEGF-eNOS axis by anti-angiogenic therapies is considered a causative factor of HT in patients, the purpose of this study was to examine whether the major eNOS non-synonymous variant c.894G>T may be associated with increased risk of developing hypertension (HT) and proteinuria (PU) in breast cancer patients treated with bevacizumab.

Patients and methods. Forty-one metastatic breast cancer patients given bevacizumab as per standard of care were enrolled. Main characteristics were: median age 49.5 years (range 29–73) at first diagnosis, 53 years (range 34–74) at metastatic disease; PS 0–1 in all patients; 4 subjects with hypertension and 1 patient with compensated cardiovascular disease at diagnosis. Twenty-six subjects had received neoadjuvant or adjuvant chemotherapy based on anthracycline and taxane; first-line chemotherapy for metastatic disease was paclitaxel plus bevacizumab for all patients; 14 subjects received hormone-therapy for metastatic disease (range 1–5 lines). Germline DNA was extracted from peripheral blood and used to screen patients for eNOS c.894G>T variant by automatic sequencing. The study was approved by the local Ethics Committee.

Results. Three patients (7.3%) were homozygous variant c.894TT, 12 (29.3%) homozygous wild-type c.894GG and the remaining 26 (63.4%) were heterozygous c.894GT. The c.894TT patients had no HT or PU at baseline and developed grade (G) 1, 2, 2 HT, respectively, and in one case PU during treatment. G1, 2 and 3 HT developed in 4, 5 and 2 c.894GG subjects, respectively, while PU was observed in 7/12 (58%) patients. The full range of HT grades and PU were observed in heterozygous subjects. Thirty-seven patients achieved one of the following: partial remission, minimal response or stable disease upon treatment with bevacizumab in combination with chemotherapy; 3 subjects had progressive disease and 1 was not evaluable.

Conclusions. The presence of the mutant T allele of c.894G>T is not associated with increased severity of HT and PU; therefore, bevacizumab can be administered at no increased risk in TT patients with respect to the wild-type GG population.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-17-06.