The significance of HOXB7 and IL17RB serum levels in prognosis of hormonally dependent breast cancer: A pilot study

Purpose: Improved prognostication of a patient's outcome could allow for personalized treatment decisions in breast cancer. Homeobox B7 (HOXB7) and interleukin 17 receptor B (IL17RB) are proteins reportedly involved in the development of hormonal therapy resistance. Their prognostic value was previously investigated in tumor tissue but recent mass spectrometric detection of HOXB7 and IL17RB proteins in serum has prompted us to perform the first prognostic evaluation of their serum levels. Patients and methods: The study included 81 premenopausal breast cancer patients that received adjuvant hormonal therapy. The median follow-up period was 61 months. HOXB7 and IL17RB serum protein levels were measured by quantitative sandwich ELISA and prognostically evaluated by Cox proportional hazards regression analysis. Results: HOXB7 protein was detected in 96.3% and IL17RB in 33.3% of serum samples. Higher levels of serum HOXB7 significantly associated with favorable disease outcome by prognosticating distant (by HR = 0.04; P = 0.001) and local recurrence (by HR = 0.03, P = 0.001). The recurrence rates in the HOXB7^high and HOXB7^low subgroups of patients (cut-off 81.5 pg/mL) were 0% and 17%, respectively. Serum IL17RB levels did not significantly associate with either local or distant events. The multivariate analysis highlighted estrogen receptor, histological grade, nodal status and HOXB7 as independent prognostic parameters. Conclusions: Our findings validate the previous mass-spectrometry data by showing that HOXB7 and IL17RB cellular proteins are detectable in serum by a standard ELISA assay. Furthermore, we show that HOXB7 serum levels are the relevant prognosticator of response to hormonal therapy. © 2021 Medical University of Bialystok