Immunotargeting of Antigen xCT Attenuates Stem-like Cell Behavior and Metastatic Progression in Breast Cancer

Abstract

Resistance to therapy and lack of curative treatments for metastatic breast cancer suggest that current therapies may be missing the subpopulation of chemoresistant and radioresistant cancer stem cells (CSC). The ultimate success of any treatment may well rest on CSC eradication, but specific anti-CSC therapies are still limited. A comparison of the transcriptional profiles of murine Her2 þ breast tumor TUBO cells and their derived CSC-enriched tumorspheres has identified xCT, the functional subunit of the cystine/glutamate antiporter system x c À , as a surface protein that is upregulated specifically in tumorspheres. We validated this finding by cytofluorimetric analysis and immunofluorescence in TUBO-derived tumorspheres and in a panel of mouse and human triple negative breast cancer cell-derived tumorspheres. We further show that downregulation of xCT impaired tumorsphere generation and altered CSC intracellular redox balance in vitro, suggesting that xCT plays a functional role in CSC biology. DNA vaccination based immunotargeting of xCT in mice challenged with syngeneic tumorsphere-derived cells delayed established subcutaneous tumor growth and strongly impaired pulmonary metastasis formation by generating anti-xCT antibodies able to alter CSC self-renewal and redox balance. Finally, anti-xCT vaccination increased CSC chemosensitivity to doxorubicin in vivo, indicating that xCT immunotargeting may be an effective adjuvant to chemotherapy. Cancer Res; 76(1); 62-72. Ó2015 AACR.

NK cells control breast cancer and related cancer stem cell hematological spread

“…1A and B, respectively), as has already been observed in previous reports. 22,24 Moreover, tumorspheres showed increased in vitro self-renewal, with respect to TUBO cells in our own experiments. This is demonstrated by the higher number of cell clones generated by tumorspheres in a limiting dilution assay (Fig.…”

“…They were propagated in vitro up to the third passage (P3, hereafter referred as tumorspheres), as previously described. 24 In vivo treatments BALB/c and C57/BL6 mice were bought from Charles River Laboratories, maintained at the Molecular Biotechnology Twenty-one days after cell injection, blood was collected and mice were sacrificed in order to analyze lung metastasis formation and immune infiltrate both by FACS and histological analysis. Lungs were removed, fixed in 4% formaldehyde solution, cut into small pieces, paraffin-embedded, sectioned and haematoxylin and eosin (H&E) stained.…”

Cripto-1 Plasmid DNA Vaccination Targets Metastasis and Cancer Stem Cells in Murine Mammary Carcinoma

“…We therefore evaluated whether Cr-1 vaccination elicits a protective immune response against Cr-1 expressing CSCs. The murine mammary carcinoma cell line TUBO acquires CSC phenotypic markers when passaged three times as spheres (P3 TUBO cells) (23,34). Over three passages in spheroid culture of TUBO, we observed a gradual increase in expression of Cr-1 (Fig.…”

“…We have found that spheroid cultures of murine breast cancer cells, which are considered to be enriched in CSCs (23,34) In patients, high Cripto-1 expression in the tumor has been associated with decreased survival and could be correlated to advanced disease (12). In addition, Cr-1 has been found in the serum of breast cancer patients, suggesting its potential function as a biomarker (43 …”

“…The injection was followed by electroporation using IGEA array needle electrode. Two weeks after the second vaccination, mice were challenged subcutaneously (s.c.) with 2x10 4 TUBO P3 spheroids as described (23). Mice were inspected weekly for the presence of the tumor, the dimension of which was reported as mean tumor diameter.…”