Bax gene expression in breast cancer

Institution: The Burnham Institute for Medical Research
Investigator(s): John Reed, M.D., Ph.D. -
Award Cycle: 1995 (Cycle I) Grant #: 1RB-0093 Award: $559,057
Award Type: Research Project Awards
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (1995)
Essentially all chemotherapeutic drugs commonly used in the treatment of cancer, as well as radiation have been shown to ultimately kill cancer cells by triggering a form of cell death called "apoptosis". Consequently, alterations in the regulation of cellular genes that control the apoptotic cell death play an important role in determining the relative chemosensitivity and resistance of tumors. Recently, we obtained evidence that the pro-apoptotic gene BAX is normally turned-on ("expressed") in breast tissue, but becomes inactive in approximately one-third of invasive breast cancers. In a study of 119 women with metastatic breast cancer, we found that patients whose tumors had lost BAX activity had poorer responses to combination chemotherapy, faster time to tumor progression, and shorter overall survival.

We study the molecular mechanisms that regulate the activity of the BAX gene in breast cancer so that we might one day be able to improve tumor responses to currently available anticancer drugs. In this regard, it has been shown that radiation and DNA-damaging anticancer drugs can induce expression of BAX, suggesting that turning on this pro-apoptotic gene may be important for chemoresponses. We have recently delineated one of the factors that can regulate BAX gene activity. This regulator of BAX is called p53, a recognized tumor suppressor gene.

Taken together, these investigations will determine the clinical relevance of decreases in BAX gene activity for women with breast cancer, and will begin to provide insights into some of the molecular mechanisms that account for loss of BAX gene expression in metastatic breast cancers.

Thus far, our attempts to understand how p53 controls BAX expression have taught us that either p53 is insufficient by itself to induce BAX in many types of cells, including human breast cancers, or that other factors are suppressing the effects of p53 on BAX. Experiments are in progress to differentiate between these two possibilities. In addition, we have extended our original analysis of BAX in human breast specimens to another 150 patients, and have confirmed that approximately one-third of patients lack BAX expression. Once the mechanisms responsible for the failure of approximately one-third breast tumors to express BAX are understood at the molecular level, then we can begin to devise strategies restoring BAX or supplanting it with something else that improves the responses of patients to chemotherapy and radiotherapy.

Final Report (1998)
Prior to initiation of this grant, we obtained evidence that a cell death (apoptosis) gene, called Bax, is normally turned-on in breast tissue, but becomes inactive in approximately one-third of invasive breast cancers. In a study of 119 women with metastatic breast cancer, we found that patients whose tumors had lost Bax activity had poorer responses to combination chemotherapy, faster time to tumor progression, and shorter overall survival. Our goal was to investigate how the amount of Bax protein is controlled in breast cancers. Thus, we could understand why Bax levels become reduced and find ways to potentially correct this problem. In parallel, we also set out to define how Bax promotes tumor cell death, with the goal of triggering apoptosis. Finally, we proposed to find the relationship between the amount of Bax in breast cancers to both patient survival and risk of relapse.

Our investigations yielded several novel insights into the mechanisms that control the output of the Bax gene in breast cancers. We found that a tumor suppressor, p53, did not generally serve to increase Bax amounts. Apparently some of the failure of p53 to stimulate Bax production is due to the apoptosis-inhibiting protein Bcl-2, which serves to silence the effect of p53 on Bax expression. Next, we obtained significant new information about the mechanisms by which Bax kills tumor cells. We found that the interaction of Bax and Bcl-2, forming heterodimers, did not appear to be essential for cell death. Other experiments indicated that Bax acts on mitochondria to stimulate cell death. Finally, we continued our comparison of Bax, Bcl-2, and p53 in breast cancer patient samples to assess their potential as biomarkers of the disease. Our work indicated that Bax was not a good independent prognostic marker of clinical outcome in patients treated primarily with surgery, but had some value when combined with analysis of bcl-2 and p53. However, samples from patients receiving chemotherapy treatment for metastatic disease show that decreased levels of Bax correlate with worse outcome. This is consistent with our prediction that this protein is a key player in cell death induced by anticancer drugs.

Our work provides insight into the mechanism of cell death regulation in breast cancer, which is important in devising new treatment strategies and rendering chemotherapy more effective. The analysis of Bax in breast cancers indicates potentially useful information, which could help clinicians in determining the optimal therapeutic approaches. Finally, we have laid the foundation for future studies on Bax and apoptosis, and for further clarifying how Bax status is related to breast cancer.

Structure-function comparisons of the proapoptoticprotein bax in yeast and mammalian cells
Periodical:Molecular and Cellular Biology
Index Medicus: Mol Cell Biol
Authors: Zha H, Fisk HA, Yaffe MP, Mahajan N, Herman B, and Reed JC
Yr: 1996 Vol: 16 Nbr: 11 Abs: Pg:6494-508

Dissociation between cell cycle arrest and apoptosis can occur in Li-Fraumeni cells heterozygous for p53 gene mutations
Index Medicus: Oncogene
Authors: Delia D, Goi K, Mizutani S, Yamada T, Aiello A, Fontanella E, and Reed JC, et al
Yr: 1997 Vol: 14 Nbr: Abs: Pg:2137-2147

Bax cleavage is mediated by calpain during drug-induced apoptosis
Index Medicus: Oncogene
Authors: Wood DE, Thomas A, Devi LA, Berman Y, Beavis RC, and Reed JC
Yr: 1998 Vol: 17 Nbr: 9 Abs: Pg:1069-1078

In vivo patterns of BVL-2 family protein expression in breast carcinomas in relation to apoptotic index and patients' menstrual status
Periodical:Journal Pathologiques
Index Medicus:
Authors: Rochaix P, Voigt J-J, Krajewski S, Reed JC, Bonnet F, and Brousset P
Yr: 1999 Vol: 187 Nbr: 4 Abs: Pg:410-415

Modulation of Bcl-2 protein levels by an intracellular anti-Bcl-2 single-chain antibody increases drug-induced cytotoxicity in the breast cancer cell line MCF-7
Periodical:Cancer Research
Index Medicus: Cancer Res
Authors: Piche A, Grim J, Rancourt C, Gomez-Navarro J, ReedJC, and Curiel DT
Yr: 1998 Vol: 58 Nbr: 10 Abs: Pg:2134-2140

Bax directly induces release of cytochrome c from isolated mitochondria
Periodical:Proceedings of the National Academy of Sciences of the United States of America
Index Medicus: Proc Nat Acad Sci, U S A
Authors: Jurgensmeier JM, Xie Z, Deveraux Q, Ellergy L, Bredesen D, and Reed JC
Yr: 1998 Vol: 95 Nbr: Abs: Pg:4997-5002

Immunohistochemical analysis of bcl-2, bax, mcl-1and bcl-X expression in ovarian surface epitelial tumors
Periodical:International Journal of Gynecol Pathol
Index Medicus: Int. J. Gynecol Pathol
Authors: Wehrli BM, Krajewski S, Gascoyne RD , Reed JC, and Gilks CB
Yr: 1998 Vol: 17 Nbr: 3 Abs: Pg:255-260

The thiol crosslinking agent diamide overcomes the apoptosis-inhibitory effect of Bcl-2 by enforcing mitochondrial permeability transition
Index Medicus: Oncogene
Authors: Zamzami N, Marzo I, Susin SA, Brenner C, Larochette N, Marchetti P, and Reed J, et al
Yr: 1998 Vol: 16 Nbr: 8 Abs: Pg:1055-63

Cytoprotection by Bcl-2 requires the pore-forming alpha5 and alpha6 helices
Periodical:Journal of Biological Chemistry
Index Medicus: J Biol Chem
Authors: Matsuyama S, Schendel SL, Xie Z, and Reed JC
Yr: 1998 Vol: 273 Nbr: 47 Abs: Pg:30995-31001

Balancing cell life and death: Bax, apoptosis, and breast cancer
Periodical:Journal of Clinical Investigation
Index Medicus: J Clin Invest
Authors: Reed JC
Yr: 1996 Vol: 97 Nbr: Abs: Pg:2403-2404

Analysis of Bax and Bcl-2 expression in p53-immunopositive breast cancers
Periodical:Clinical Cancer Research
Index Medicus: Clin Cancer Res
Authors: Krajewki S, Edgerton S, Moore II DH, Krajewska M, and Reed JC
Yr: 1997 Vol: 3 Nbr: Abs: Pg:199-208

Estrogen increases intracellular p26Bcl-2 to p21Bax ratios and inhibits taxol-induced apoptosis of human breast cancer Mcf-7 cells
Periodical:Breast Cancer Research and Treatment
Index Medicus: Breast Cancer Res Treat
Authors: Huang Y, Ray S, Reed JC, Ibrado AM, Tang C, Nawabi A, Bhalla K
Yr: 1997 Vol: 42 Nbr: Abs: Pg:73-81

Apoptosis in the terminal endbud of the murine mammary gland: a mechanism of ductal morphogenesis
Index Medicus:
Authors: Humphreys RC, Krajewska M, Krnacik S, Jaeger R, Weiher H, Krajewski S, Reed JC, Rosen JM
Yr: 1996 Vol: 122 Nbr: 12 Abs: Pg:4013-22