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Fighting Tumors with Tumors

By Sean Henahan, Access Excellence 

Farmington, CT (10/3/97)- An innovative approach to cancer therapy involving the use of proteins purified from tumor cells may provide more targeted treatment for cancer patients.

Working with mice in the laboratory, researchers the Center for Immunotherapy of Cancer and Infectious Diseases at the University of Connecticut School of Medicine reported promising results when immunizing mice with  heat shock proteins derived from the mice's own tumors. 

The researchers injected mice with heat shock proteins  purified from the animals' tumors. This resulted in retarded progression of the primary lung cancer, melanoma, and colon cancer. The immunotherapy also reduced metastasis, and prolonged the lifespan of the animals. The effect on metastatic (spreading) cancers is especially important, as these kinds of cancers have proven to be among the most difficult to treat. 

The approach to immunotherapy of cancer described in the report should be applicable to virtually all forms of cancer. Heat shock proteins can be purified from a tumor specimen removed by surgery or biopsy. The versatility of heat shock proteins in the treatment of cancer derives from their normal physiological role in cells. These proteins play a role in protein trafficking, whereby they keep other proteins in their correct shape and location. When these molecular chaperones are purified from cells, they bring along peptides derived from other proteins expressed in that cell, providing a molecular "fingerprint" of the cell's content. Vaccination with the HSP-peptide complexes purified from cancer cells has the potential to specifically stimulate the immune system to attack cells bearing those peptides, i.e., the cancer cells themselves, the researchers note.

"The HSP-peptide complex vaccination is perhaps the first general principle of immunization which now has shown to be effective against a wide variety of pre-existing cancers," said Pramod K. Srivastava, Ph.D., of the University of Connecticut School of Medicine and Principle Investigator for the project. "Decades of research suggests that tumors are distinct from one individual to another, with each tumor containing its own unique set of mutations. The task of identifying each of these mutations in individual cancer patients -- with the intent of targeting them immunotherapeutically -- is therefore impractical. In contrast, the process of purifying HSPs is the same for each patient's tumor and is relatively simple." 

Phase I clinical trials, designed to measure the safety of new drugs, are now underway with a heat-shock protein based-vaccine in patients with  pancreatic cancer. The vaccines are being prepared from individual cancer patients' tumors. Phase I clinical trials for the treatment of melanoma and renal cell carcinoma are expected to start later this year. 

The research appears in the October 3, 1997 issue of Science.

Related information on the Internet
AE: p73 Tumor Suppressor
AE: Molecular Biology of Cancer
AE: Lymphoma Vaccine 

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