Inclusion Criteria:

- Patients must have cytologically/histologically documented locally advanced or
metastatic breast cancer with either:

1. Progression on treatment with any aromatase inhibitor for metastatic disease;

2. Recurrence while on adjuvant aromatase inhibitors or within 12 months of
completion;

3. Recurrence after having completed adjuvant tamoxifen for at least 12 months;

4. Patient who are not candidates for or are intolerant of aromatase inhibitor
treatment;

5. Patients are allowed (but not required) to have one prior chemotherapy regimen
for metastatic disease.

- Tumors must express estrogen or progesterone receptor.

- Patients are eligible regardless of the menopausal status.

- Age > 18 years old

- Patients must have Eastern Cooperative Oncology Group (ECOG) performance status 0-2.

- Patients must be able to give informed consent and able to follow guidelines given in
the study.

- Patients must have acceptable organ function, as defined by the following laboratory
parameters: white blood count (WBC) >3.0 x 10^9/L; absolute neutrophil count (ANC)
>1.5 x 10^9/L; hemoglobin (Hgb) >10.0g/dL; platelets (PLT) >100 x 10^9/L, Bilirubin <
2.0 mg/dl, aspartate aminotransferase/alanine aminotransferase (AST/ALT) < 2.5 X
upper limit of normal (ULN), Creatinine <1.8 mg/dl (Creatinine clearance >60 ml/min).

- Women of childbearing age must have a negative pregnancy test. All patients of
reproductive potential must use an effective method of contraception during the study
and 6 months following termination of treatment. (Not applicable to patients with
bilateral oophorectomy and/or hysterectomy or to female patients who are older than
50 years and have not had a menstrual cycle in more than one year.

- Patients must have measurable disease by RECIST criteria by staging studies performed
within 30 days of enrollment. For patients with bone only disease: For this protocol
isolated bone lesions can be classified as target lesions if they are measurable by
MRI at screening and must be followed by MRI.

- Both men and women of all races and ethnic groups are eligible for this trial.

Exclusion Criteria:

- Patients must not have received tamoxifen for metastatic disease.

- Patients must not have evidence of significant active infection (e.g., pneumonia,
cellulitis, wound abscess, etc.) at time of study entry.

- Patients must be disease-free of prior invasive malignancies for > 5 years with the
exception of: curatively-treated basal cell or squamous cell carcinoma of the skin,
carcinoma in situ of the cervix.

- Pregnant and breast-feeding women are excluded from the study because effects on the
fetus are unknown and there may be a risk of increased fetal wastage.

- Patients with uncontrolled central nervous system (CNS) metastasis or a history of
seizures are excluded. Patients with stable CNS metastasis (either surgically
resected, treated with gamma knife or stable for 3 months following whole brain
radiation therapy [WBRT] are eligible). Patients with stable brain metastases will
need an MRI within 4 weeks prior to start of therapy.

- Patients may not be receiving any other investigational agents and must have stopped
all other histone deacetylase inhibitors (including Valproic acid) or other hormonal
therapies.

- Patients must have discontinued their prior therapies for breast cancer and radiation
therapy for a minimum of 3 weeks, patient is excluded if radiation therapy was given
to a single measurable lesion and the disease is otherwise not measurable.

- Patients are excluded if they have any known hypersensitivity reaction to tamoxifen.

- Patient with a history of blood clots are not eligible.

- Women who have abnormal vaginal bleeding and/or endometrial hyperplasia or cancer are
not eligible.

- Patients with evidence of visceral crisis are not eligible for this study.