This study will examine blood, bone marrow, tumor and tissue samples from patients with cancer to study tumor resistance to chemotherapy (drug treatment). Many patients with cancer improve initially with chemotherapy, but then have a disease relapse, after which their tumor no longer responds to treatment. Other patients' tumors are drug-resistant from the start. The study will look for "resistance factors"-substances in blood and tissues that render tumors resistant to chemotherapy. The findings may provide information needed to develop methods of combating drug resistance.

Patients with cancer who are 18 years or older may be eligible for this study. Participants will have 40 milliliters (3 tablespoons) of blood drawn at the beginning of the study; additional samples will be obtained periodically during the course of treatment. A small sample of tumor or normal tissue will be taken from patients who undergo surgery or tumor biopsy (removal of a small piece of tumor) for medical reasons or as part of a research treatment protocol. Patients who do not require surgery or biopsy may be asked permission to obtain a tumor sample. Depending on the location of the tumor, this may be done by: 1) withdrawing bone marrow through a small needle; 2) removing fluid from the chest or abdomen; 3) removing a small tumor sample through a needle; or 4) removing the sample with a small incision into or around the tumor. These procedures will be done only if they are of low risk to the patient.