Side Population Cell Level in Human Breast Cancer and Factors Related to Disease-free Survival

Side population (SP) cells have stem cell-like properties with a capacity for self-renewal and are resistantto chemotherapy and radiotherapy. Therefore the presence of SP cells in human breast cancer probably hasprognostic value.
Objective: To investigate the characteristics of SP cells and identify the relationship betweenthe SP cells levels and clinico-pathological parameters of the breast tumor and disease-free survival (DFS) inbreast cancer patients. Materials and
Methods: A total of 122 eligible breast cancer patients were consecutivelyrecruited from January 1, 2006 to December 31, 2007 at Yunnan Tumor Hospital. All eligible subjects receivedconventional treatment and were followed up for seven years. Predictors of recurrence and/or metastasis andDFS were analyzed using Cox regression analysis. Human breast cancer cells were also obtained from freshhuman breast cancer tissue and cultured by the nucleic acid dye Hoechst33342 with Verapami. Flow cytometry(FCM) was employed to isolate the cells of SP and non-SP types.
Results: In this study, SP cells were identifiedusing flow cytometric analysis with Hoechst 33342 dye efflux. Adjusted for age, tumor size, lymph nodal status,histological grade, the Cox model showed a higher risk of recurrence and/or metastasis positively associatedwith the SP cell level (1.75, 1.02-2.98), as well as with axillary lymph node metastasis (2.99, 1.76-5.09), pathologyinvasiveness type (1.7, 1.14-2.55), and tumor volume doubling time (TVDT) (1.54, 1.01-2.36).
Conclusions: TheSP cell level is independently associated with tumor progression and clinical outcome after controlling for otherpathological factors. The axillary lymph node status, TVDT and the status of non-invasive or invasive tumorindependently predict the prognosis of breast cancer.