OBJECTIVETo explore the relationship between a proliferation-inducing ligand (APRIL) expression in primary tumor foci of breast cancer and the patients' prognosis.

METHODSParaffin sections of surgical specimens were retrospectively collected from 130 stage I-III breast cancer patients who received surgery between January 2000 and December 2002 in our hospital. Immunohistochemistry was used to assess APRIL expression intensity in the tumor cells and density of interstitial APRIL-positive cells, and their association was analyzed with the density of interstitial CD4⁺ and CD8⁺ cells and with the histopathologic features, overall survival (OS), and disease-free survival (DFS) of the patients.

RESULTSAPRIL positive staining was found in the cytoplasm of the tumor cells, interstitial cells, and the extracellular matrix. APRIL intensity in the tumor cells was positively correlated with the density of interstitial APRIL-positive cells (P=0.009) and Ki67 (P=0.003). The density of interstitial APRIL-positive cells was positively correlated with the density of interstitial CD4⁺ cells (P<0.001) and CD8⁺ cells (P<0.001). In hormone receptor negative patients (ER- and PR-), multivariate COX regression identified the density of interstitial APRIL-positive cells as a positive prognostic factor for DFS (HR=0.313, 95% CI=0.107-0.920, P=0.035). CONCLUSIONSl APRIL is widely expressed in the interstitial immune cells in breast cancer. APRIL staining intensity in the tumor cells is positively correlated with tumor proliferation, indicating that the immune cells might promote tumor proliferation by secreting APRIL. A greater density of interstitial APRIL-positive cells is associated with a good prognosis in hormone receptor-negative patients.