DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed adenocarcinoma of the breast

  • Stage IV disease
• Tumor blocks and/or slides from original diagnosis or metastatic disease work-up must be available

• Progressive disease after 1 or 2 prior chemotherapy regimens for metastatic disease

  • Chemotherapy regimen(s) may have included trastuzumab (Herceptin®) for HER2/neu-positive disease
• Measurable disease, defined as ≥ 1 unidimensionally measurable lesion > 20 mm by conventional techniques OR > 10 mm by spiral CT scan
• No known brain metastases unless they are controlled after prior therapy AND patient has not been treated with steroids within the past 2 months

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Female or male

Menopausal status

• Not specified

Performance status

• ECOG 0-2

Life expectancy

• More than 6 months

Hematopoietic

• Absolute neutrophil count ≥ 1,000/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• Bilirubin ≤ 2 mg/dL
• AST and ALT ≤ 3 times upper limit of normal

Renal

• Creatinine ≤ 1.6 mg/dL OR
• Creatinine clearance ≥ 60 mL/min

Cardiovascular

• No symptomatic congestive heart failure
• No unstable angina pectoris
• No cardiac arrhythmia

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

• No history of allergic reaction attributed to compounds of similar chemical or biological composition to study drug, including any of the following:

  • Sodium butyrate
  • Trichostatin A
  • Trapoxin
  • MS-27-275
  • Depsipeptide
• No psychiatric illness or social situation that would preclude study compliance
• No ongoing or active infection
• No other uncontrolled illness

PRIOR CONCURRENT THERAPY:

Biologic therapy

• See Disease Characteristics
• No concurrent filgrastim (G-CSF) for chemotherapy-induced neutropenia

Chemotherapy

• See Disease Characteristics
• More than 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)

Endocrine therapy

• See Disease Characteristics
• Prior hormonal therapy allowed

Radiotherapy

• More than 4 weeks since prior radiotherapy

Surgery

• Not specified

Other

• Recovered from all prior therapy
• Prior adjuvant therapy for metastatic disease allowed
• At least 2 weeks since prior valproic acid
• No other concurrent investigational agents
• No other concurrent anticancer therapy
• No concurrent combination antiretroviral therapy for HIV-positive patients