Abstract P4-09-05: Microarray anlyses of breast cancers identify CH25H, a cholesterol gene, as a potential marker and target for late metastatic reccurences.
Authors: Saghatchian M , Mittempergher L , Michiels S , Wolf D , Canisius SV , Dessen P , Delaloge S , Lazar V , Benz SC , Roepman P , Glas AM , Tursz T , Bernards R , van't Veer LJ 
Published: August 2014

Background: However hormone receptor–positive, early-stage breast cancer is a disease with a long natural history and improved survival with 5-year adjuvant endocrine treatments. Yet late recurrence remains an important issue in adjuvant therapy. Predictors of late recurrence are not yet well characterized.

Method: A total of 252 breast primary tumors were selected at the Netherlands Cancer Institute from retrospective series of ER+, HER2− breast cancer patients with a follow-up of at least 10 years. Gene expression analysis was performed using Agilent 4×44K microarrays. In order to identify genes associated to late survival differences, we used the survdiff function implemented in the R package survival and we set the parameter rho to −1 to give weight to the later part of the survival curve. The survdiff function was applied to each probe individually for DMFS time considering the probe as a covariate dichotomized into 2 groups (above and below the median expression across all samples). The parameter “strata” was used to stratify the 140 patients based on additional clinico-pathological parameters (Grade, Diameter, Lymph node status and MammaPrint), in order to find genes that add prognostic value to those parameters already known. This approach uses the distant-metastasis free survival (DMFS) time as a continuous variable.

Results: After univariate analysis, MammaPrint, diameter, lymph node status and grade were significantly associated to late DMFS differences (Chi-square test p-values equal to 0.016, 0.004, &lt;0.001 and 0.016 respectively). Two genes, cholesterol 25-hydroxylase (CH25H) and follistatin-like 4 (FSTL4) were selected as significantly associated to late DMFS after correction for multiple testing (p-value=0.01). Interestingly CH25H is part of the 241-gene signature previously described (SABCS 2011). After Cox regression analysis, patients with high expression of CH25H (‘intensity above median’) showed an odds ratio (OR) of 0.28 (95% CI=0.17–0.44) compared to patients with a low expression of CH25H (‘intensity below median’). For the gene FSTL4, OR was 2.42 (95% CI=1.54–3.80) compared to patients with low expression of FSTL4.

In order to independently validate the prognostic power of these two genes, we tested their performance in the validation set of treated patients (n = 112) and in three publicly available datasets. In all datasets, the CH25H gene confirmed to be significantly associated to metastasis-free survival time in all tested series.

Conclusions: These results might indicate that CH25H is an independent marker of late metastatic relapses. CH25H catalyzes the formation of 25-hydroxycholesterol from cholesterol, leading to repress cholesterol biosynthetic enzymes. In the last years, it is emerging that lipid metabolism plays an important role in breast cancer development and progression. Taken together, these findings make the CH25H gene a potential target for late metastasis control in breast cancer. These results warrant further prospective investigation and functional characterization of CH25H in this setting.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-09-05.