Medical Summary
Women with estrogen receptor positive breast cancer cells usually respond to antiestrogen therapy with a variable duration of response. Metastatic breast cancer which is hormone-insensitive can respond to cytotoxic chemotherapy, but the duration of response is short and the median survival of these patients is less than 2 years. 5-Aza-2'-deoxycytidine (5 AZA-CdR) is an antineoplastic agent with potential effectiveness in treating breast cancer. An interest in 5-AZA-CdR as an antitumor agent has been generated by reports of its activation of tumor suppressor genes. In general, DNA methylation blocks gene expression whereas demethylation by 5-AZA-CdR produces gene activation. 5-AZA-CdR can lead to the activation of the expression of tumor suppressor genes, providing a rationale for its use in breast cancer. The incorporation of 5-AZA-CdR into specific DNA sequences results in the inhibition of DNA methylation. In general, many genes are silent when methylated, but become active when hypomethylated. One of the effects produced by 5 AZA-CdR is to activate silent genes and this can result in the induction of cellular differentiation and the loss of the malignant phenotype. Tumor suppressor genes may be inactivated (silenced) by chromosomal deletion, mutation and by aberrent hypermethylation of their promoters. The expression of several different types of tumor suppressor genes have been shown to be silenced by DNA methylation and their expression can be activated by treatment of tumor cells with 5 AZA-CdR. Other types of genes that may play a role in the development of malignant neoplasia and can also be silenced by DNA methylation include: E-cadherin, a tumor invasion inhibitor, which potentially can repair mutations; O6 methylguanine methyltransferase which can remove adducts from DNA resulting from treatment with anticancer drugs such as BCNU can reduce the incidence of mutation; and Thrombospondin 1 (TSP-1), an angiogenesis inhibitor which will impede tumor growth by inhibiting the formation of blood vessels. In a phase I study of 5-AZA-CdR in patients with acute leukemia , 6 complete remissions and 4 partial remissions were seen. The major side effects were myelosuppression, nausea and vomiting. Other promising activity has been seen in patients solid tumors of the head and neck and lung . Since the progression of breast cancer is slower than lung cancer it may be possible to obtain a better response in patients with breast cancer. In this study 20 patients will be treated. Since 5-AZA-CdR is a differentiating agent and there is a delay in the onset of its antitumor action, patients will be treated for at least 5 cycles after which time they will be assessed for response. A biopsy of the breast tumor will be used for DNA methylation analysis. The methylation status of various genes targeted by 5-AZA-CdR will be examined and correlated to tumor response.

References:

1. Jones PA., Taylor SM., et al., Cell-cycle specific activation of an inactive X chromosome locus by 5 azadeoxycytidine. Proc. Natl. Acad. Sci. (U.S.A.) 79:1215-1219 (1982).
2. Jones PA. DNA methylation errors and cancer. Cancer Res. 56: 2463-2467 (1996).
3. Momparler RL., et al., Induction of differentiation and inhibition of DNA methylation in HL-60 myeloid leukemic cells by 5-Aza-2'-deoxycytidine. Leukemia Res. 9:1361-1366 (1985).

Lay Summary
A number of potentially important genes do not function normally in cancer cells. These include genes that suppress the growth of tumors, inhibit their spread, and that make them sensitive to treatments like tamoxifen which have limited toxicity. A main reason why a number of these genes are not working is that the part of the gene that controls expression (promoter) has accumulated molecules called Òmethyl groupsÓ in some of its bases. This results in a ÒsilencingÓ or turning off of gene expression. 5-Aza-2'-deoxycytidine is drug that limits the addition of methyl groups to genes, and in the laboratory can be shown to allow such genes to turn back on. This drug has been given to cancer patients in the past, and in some cases was shown to have activity, with limited toxicity. This protocol is designed to see whether it is possible to give the drug and cause re-expression of these critical genes, in patients with breast cancer. If so, the patients may become more sensitive to treatments which were otherwise not helpful. In order to learn about this, we have designed a study where women with breast cancer that has not responded to previous treatment may be eligible. They must have metastatic disease that is accesable for biopsy, with a small needle, before and after the first treatment only (usually this means skin metastases). Patients are very closely followed for toxic effects, as well as to determine changes in the tumor size. The biopsied tissues are studied for an effect on the genes described above. This protocol is supported by the Centre for Translational Research with funds provided by the Montreal Breast Cancer Foundation. It evolves from work done in research laboratories at Hopital Ste. Justine.

1. Pathologically confirmed Diagnosis of metastatic breast cancer.
2. Patients must have at least on bidimensionally measurable lesion either clinically or radiographically.
3. Patients must have at least one lesion amenable to serial biopsy.
4. Age > or greater 18 years
5. Patients must be able to give informed consent.
6. Patients must have documented disease progression after at least one course of standard chemo- or hormonal (in the case of patients with positive estrogen or progesterone receptor disease) therapy. Progression during the first 6 weeks of hormonal therapy may represent a therapy induced flare and should not necessarily be accepted as documentation of hormone refractory status.
7. Patients must have recovered from the acute effects of prior chemotherapy or radiation therapy. A minimum of 4 weeks must have elapsed since the previous chemotherapy or radiotherapy. ( 6 weeks if prior therapy included the use of mitomycin C.)
8. Karnofsky performance status > (or equal to) 70%
9. Absolute granulocyte count > (or equal to) 1.5 x 109/L
10. Platelets >(or equal to) 100 x 109/L
11. Bilirubin <(or equal to) 1.5 x upper normal limit (UNL)
12. AST and ALT <(or equal to) 2 x UNL
13. Serum creatinine <(or equal to) 1.5 x UNL or 24 creatinine clearance >(or equal to) 60 mL/min
14. Patients must give informed consent and sign the written consent form approved for this trial.