A Switch Between Cytoprotective and Cytotoxic Autophagy in the Radiosensitization of Breast Tumor Cells by Chloroquine and Vitamin D.
Summary of "A Switch Between Cytoprotective and Cytotoxic Autophagy in the Radiosensitization of Breast Tumor Cells by Chloroquine and Vitamin D."
Calcitriol or 1,25-dihydroxyvitamin D3, the hormonally active form of vitamin D, as well as vitamin D analogs, has been shown to increase sensitivity to ionizing radiation in breast tumor cells. The current studies indicate that the combination of 1,25-dihydroxyvitamin D3 with radiation appears to kill p53 wild-type, estrogen receptor-positive ZR-75-1 breast tumor cells through autophagy. Minimal apoptosis was observed based on cell morphology by DAPI and TUNEL staining, annexin/PI analysis, caspase-3, and PARP cleavage as well as cell cycle analysis. Induction of autophagy was indicated by increased acridine orange staining, RFP-LC3 redistribution, and detection of autophagic vesicles by electron microscopy, while autophagic flux was monitored based on p62 degradation. The autophagy inhibitors, chloroquine and bafilomycin A1, as well as genetic suppression of the autophagic signaling proteins Atg5 or Atg 7 attenuated the impact of the combination treatment of 1,25 D3 with radiation. In contrast to autophagy mediating the effects of the combination treatment, the autophagy induced by radiation alone was apparently cytoprotective in that either pharmacological or genetic inhibition increased sensitivity to radiation. These studies support the potential utility of vitamin D for improving the impact of radiation for breast cancer therapy, support the feasibility of combining chloroquine with radiation for the treatment of breast cancer, and demonstrate the existence of an "autophagic switch" from cytoprotective autophagy with radiation alone to cytotoxic autophagy with the 1,25 D3-radiation combination.
Affiliation
Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, PO Box 980035, Richmond, VA, 23298, USA.
Journal Details
This article was published in the following journal.
Name: Hormones & cancer
ISSN: 1868-8500
Pages:
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21887591
- DOI: http://dx.doi.org/10.1007/s12672-011-0081-7
Medical and Biotech [MESH] Definitions
Genes, Switch
Genes that cause the epigenotype (i.e., the interrelated developmental pathways through which the adult organism is realized) to switch to an alternate cell lineage-related pathway. Switch complexes control the expression of normal functional development as well as oncogenic transformation.
Breast Cyst
A fluid-filled closed cavity or sac that is lined by an EPITHELIUM and found in the BREAST. It may appear as a single large cyst in one breast, multifocal, or bilateral in FIBROCYSTIC BREAST DISEASE.
Carcinoma, Ehrlich Tumor
A transplantable, poorly differentiated malignant tumor which appeared originally as a spontaneous breast carcinoma in a mouse. It grows in both solid and ascitic forms.
Ca-125 Antigen
Carbohydrate antigen most commonly seen in tumors of the ovary and occasionally seen in breast, kidney, and gastrointestinal tract tumors and normal tissue. CA 125 is clearly tumor-associated but not tumor-specific.
Fibrocystic Breast Disease
A common and benign breast disease characterized by varying degree of fibrocystic changes in the breast tissue. There are three major patterns of morphological changes, including FIBROSIS, formation of CYSTS, and proliferation of glandular tissue (adenosis). The fibrocystic breast has a dense irregular, lumpy, bumpy consistency.
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