Prognostic value of IMP3 expression as a determinant of chemosensitivity in triple-negative breast cancer

Triple negative breast cancer (TNBC) has an aggressive phenotype and poor prognosis. Neoadjuvant chemotherapy (NAC) is often used to treat TNBC, but some patients are resistant to NAC. We postulated that a subpopulation of TNBC cells expressing IMP3, an oncofetal protein, could be resistant to NAC, contributing to the poor prognosis. We investigated immunohistochemical expression of IMP3 in 42 TNBC patients who underwent NAC in association with clinical outcomes. The patients were divided into IMP3 positive (+) (n = 19) and negative (−) (n = 23) groups. High Ki67 positivity was detected in 13 patients of the IMP3 + group and 8 cases in the IMP3 - group (p = 0.03). While 9 patients in the IMP3 - group (39%) were responders, the majority of the IMP3 + patients (84.2%) were non-responders (p = 0.01). In a Cox proportional hazard model, IMP3 expression was independently associated with poor NAC response and clinical outcomes (p = 0.03 and 0.046, respectively). The IMP3 + group showed a tendency toward shorter overall survival compared to the IMP3 - group with marginal significance (p = 0.07). These findings suggest that IMP3 + tumor cells contributed to the poor clinical outcomes by exerting a chemoresistance to NAC, and that IMP3 expression has prognostic value as a biomarker for chemosensitivity and overall survival in TNBC.