High levels of nuclear heat-shock factor 1 (HSF1) are associated with poor prognosis in breast cancer

Abstract

Heat-shock factor 1 (HSF1) is the master transcriptional regulator of the cellular response to heat and a wide variety of other stressors. We previously reported that HSF1 promotes the survival and proliferation of malignant cells. At this time, however, the clinical and prognostic significance of HSF1 in cancer is unknown. To address this issue breast cancer samples from 1,841 participants in the Nurses' Health Study were scored for levels of nuclear HSF1. Associations of HSF1 status with clinical parameters and survival outcomes were investigated by Kaplan-Meier analysis and Cox proportional hazard models. The associations were further delineated by Kaplan-Meier analysis using publicly available mRNA expression data. Our results show that nuclear HSF1 levels were elevated in ∼80% of in situ and invasive breast carcinomas. In invasive carcinomas, HSF1 expression was associated with high histologic grade, larger tumor size, and nodal involvement at diagnosis (P < 0.0001). By using multivariate analysis to account for the effects of covariates, high HSF1 levels were found to be independently associated with increased mortality (hazards ratio: 1.62; 95% confidence interval: 1.21-2.17; P < 0.0013). This association was seen in the estrogen receptor (ER)-positive population (hazards ratio: 2.10; 95% confidence interval: 1.45-3.03; P < 0.0001). In public expression profiling data, high HSF1 mRNA levels were also associated with an increase in ER-positive breast cancer-specific mortality. We conclude that increased HSF1 is associated with reduced breast cancer survival. The findings indicate that HSF1 should be evaluated prospectively as an independent prognostic indicator in ER-positive breast cancer. HSF1 may ultimately be a useful therapeutic target in cancer.

Fig. 1.

HSF1 protein is increased in breast cancer. (A) Characterization of HSF1 antibody. Immunoblot analysis of spleen lysates from HSF1 wild-type (+/+) and HSF1 null (−/−) mice. (B) IHC of mouse brain from HSF1 wild-type and HSF1 null mice, long development. (Scale bars: 20 μM.) (C Upper) HSF1 immunoblot analysis of matched pairs of invasive ductal carcinoma and adjacent normal breast from seven patients. (Lower) Protein staining for loading comparison.

Fig. 2.

HSF1 is increased and localized to the nucleus in invasive and in situ breast carcinoma. Photomicrographs of H&E-stained sections and HSF1 IHC of invasive ductal carcinoma (A and B) and the preinvasive lesion, DCIS (C and D). Nonneoplastic breast epithelium is indicated by arrows, and neoplastic cells are indicated by the arrowheads. (E) Representative photomicrographs of tumors from the NHS TMAs that were stained by HSF1 IHC and that were scored as having either no (−), low, or high nuclear HSF1 expression. This example with no nuclear HSF1 expression (−) demonstrates weak immunoreactivity in the cytoplasm. (Scale bar: 20 μM.)

Fig. 3.

HSF1-positive tumors are associated with decreased survival in ER-positive breast cancer. (A) Kaplan–Meier analysis of all individuals with breast cancer that were scored in this study. (B–D) Kaplan–Meier analysis of participants with HER2-positive (HER2+) breast cancer (B), triple-negative breast cancer (C), and ER-positive (ER+) breast cancer (D) that had HSF1 in the nucleus (HSF1 +) or that had no detectable nuclear HSF1 (HSF1 −). In these analyses, low and high nuclear HSF1 expressors were included in the HSF1 + group. (E and F) Kaplan–Meier analysis of individuals with ER+, HER2+, and triple-negative breast cancer (E) or with only ER+ breast cancer (F) expressing no nuclear HSF1, low nuclear HSF1, or high nuclear HSF1. Data are from the NHS (1976–1997). Log-rank P values are shown.