DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed solid tumor malignancy

  • Recurrent or refractory disease
  • No available curative therapy or patient refused standard therapy
• Measurable or evaluable disease

• No active CNS metastases or carcinomatous meningitis

  • Patients with CNS metastases are eligible provided it has been at least 3 months since prior therapy to the brain and are off all steroids without progressing CNS disease

PATIENT CHARACTERISTICS:

• ECOG performance status 0-2
• Life expectancy > 4 months
• ANC ≥ 1,200/mm^3
• Platelet count ≥ 100,000/mm^3
• Absolute lymphocyte count ≥ 800/mm^3
• Hemoglobin ≥ 9.0 g/dL
• Serum total bilirubin ≤ 1.5 times upper limit of normal (ULN)
• ALT and AST ≤ 2.5 times ULN
• Serum creatinine ≤ 1.5 times ULN OR creatinine clearance ≥ 50 mL/min
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 1 month after completion of study therapy
• Normal EKG (benign variants or abnormalities associated with any condition currently responding to appropriate care [e.g., controlled hypertension with minimal or moderate left ventricular hypertrophy, or controlled atrial fibrillation] allowed)

• No significant or uncontrolled cardiovascular disease, including any of the following:

  • Uncontrolled hypertension (patients eligible if BP ≤ 150/90 mmHg on stable antihypertensive regimen)
  • NYHA class II-IV congestive heart failure
  • Peripheral vascular disease ≥ grade 2
  • Significant ventricular arrhythmias requiring medication
  • Myocardial infarction or unstable angina within the past 6 months

• No history of gastrointestinal disease causing malabsorption or obstruction, including, but not limited to, any of the following:

  • Crohn's disease
  • Celiac sprue
  • Tropical sprue
  • Bacterial overgrowth/blind loop syndrome
  • Gastric bypass surgery
  • Strictures
  • Adhesions
  • Achalasia
  • Bowel obstruction
  • Extensive small bowel resection
• No other active malignancy
• No active uncontrolled infection requiring antibiotics within the past week (including unexplained fever > 38.1°C or 100.6°F)
• No history of or active autoimmune disease (e.g., systemic lupus erythematosus, rheumatoid arthritis, scleroderma, or dermatomyositis)
• No condition, psychiatric or otherwise, that would preclude informed consent, consistent follow up, or compliance with any aspect of the study (e.g., untreated schizophrenia or other significant cognitive impairment)
• No HIV or hepatitis B or C positive serology
• No other acquired/inherited immunodeficiencies
• No residual toxicity from prior therapy > grade 1

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• At least 4 weeks since prior major surgery or systemic chemotherapy
• At least 2 weeks since prior localized radiotherapy
• No prior organ transplantation

• No concurrent immunosuppressive therapy including systemic corticosteroid therapy, methotrexate, cyclosporine, tacrolimus, or sirolimus

  • Concurrent inhaled or topical corticosteroids allowed
• No concurrent supplements containing L-tryptophan or its derivatives