94-04-28 UVa have identified a molecular cancer marker or peptide

                  EMBARGOED UNTIL 6 P.M., EST, THURSDAY, APRIL 28

                                      Contact: Marguerite Beck

     CHARLOTTESVILLE, Va., April 29 -- Findings published in
today's Science may bring researchers one step closer to
developing a vaccine that would harness the body's own immune
system to fight a form of cancer.
     For the first time scientists at the University of Virginia
have identified a molecular cancer marker or peptide that is
recognized by the immune systems of multiple patients suffering
from melanoma, a serious form of skin cancer.  With the
identification of this peptide, U.Va. researchers have homed in on
the specific part of the melanoma cell that stimulates the body's
immune system to attack and kill the cancer.
     Researchers extracted peptides off the surface of melanoma and
analyzed them with tandem mass spectrometry to determine their
chemical structure.  Using methods developed at U.Va. by chemistry
professor Donald Hunt, the researchers discovered which of the more
than 10,000 peptides present on each cell would trigger the body's
immune response.
     "By isolating a peptide that the immune system actually sees
on the cancer cell surface, we are better able to understand the
body's immune response to melanoma and hopefully harness it for
treatment," said Dr. Craig Slingluff, assistant professor of
surgery at U.Va. and co-investigator of the study.
     Normally, cells transport to their outer surfaces fragments of
each of the thousands of proteins they are manufacturing at any
given moment.  These protein fragments are called
peptides.  Should a cell become infected by a virus, a few foreign
peptides of viral origin will be mixed in among the thousands of
normal cell peptides on that cell's surface.  These foreign
peptides elicit a response from the body's immune system, which
leads to the destruction of the infected cell.
     Although melanoma is not caused by a virus, these cancer cells
also generate melanoma-specific peptides that stimulate the immune
system to attack the tumor.  For reasons not yet understood by
researchers, the immune response is often insufficient to kill the
tumor while it is still in the body.  Until now, the strategy used
for melanoma vaccines has been to remove tumor cells from a patient
with advanced melanoma, modify it in some way to get a stronger
immune response and inject it back into the same patient.
     "The problem with this approach is that you must wait until
the patient is in the advanced stages of the disease to be able to
extract enough tumor cells to make a vaccine, and that vaccine will
work only for that individual patient," said Dr. Victor Engelhard,
professor of medicine and microbiology.  "Peptides are a more
convenient vehicle to deal with than a tumor cell.  We now have an
approach to treating people from whom there is no possibility of
isolating a tumor.  Another advantage is that we can make about a
gram of this peptide in the lab in about 24 hours -- enough to
potentially treat hundreds of people."
     The peptide isolated by U.Va. researchers is present in about
40 percent of the Caucasian population, which is at the highest
risk for melanoma.  "For the remaining 60 percent," Engelhard said,
"we will need to identify additional melanoma-specific peptides."
     Researchers at U.Va. hope to begin clinical trials using this
peptide within the next several months.

More information:
Dr. Victor Engelhard 804-924-2423 or 804-924-1706
Donald Hunt Ph.D. 804-924-3610 or 804-924-7994


[Submitted by:  (cab2j@dmt03.mcc.virginia.edu)
               28 Apr 94 15:14:07 EDT]