~ Sunday, December 1, 1985 — North Shore News Test finds early signs of cancer RESEARCHERS at the British Columbia Cancer Research Centre's Environ- ment Carcinogenesis Unit have developed a fast and inexpensive test that detects genetic damage caused by cancer-causing substances (carcinogens) in human cells, Since such damage is an early warning sign of cancer, the test is now being used to assess cancer risks in large populations and then follow how effective different pro- cedures are for reducing such risks. “We focus on this early damage because it's the best time co intervene. If you can block carcinogen damage, you can reduce your cancer tisk,"’ says Dr. Miriam Rosin, a pathologist and one of the senior investigators involved in the test's development. In a normal cell, the genetic material, or DNA, is packaged in discrete units, known as chromosomes. The chromosomes, in turn, are contained in a small circular body within the cell, called the nucleus. When a carcinogen bom- bards a cell it shatters chromosomes. Sometimes the resulting genetic damage is repaired by the body. But incomplete repair may result “‘micronuclei’’: tiny nuclei which form outside the main nucleus and contain the chromosome fragments pro- duced by the carcinogen. Using a stain that specifically hightights micronuclei in cells, resear- chers can count the micronuclei undef a_ light microscope. GREATER RISK The B.C. team—Dr, Rosin, Dr. Hans F. Stich, a medical geneticist, zoologist and pathologist, and Dr. Richard H.C. San, also a medical geneticist—has shown that the more micronuclei present, the greater the cancer risk. Dr. Rosin says the chromosome fragments pro- duced by a carcinogen can “float around’’ and ran- domly reattach to other chromosomes. If a chromosome fragment carrying a cancer-causing gene (an ‘‘oncogene’’, thought to be inactive when attached to an undamaged chromasome) reattaches to another chromosome, the incogene may be. triggered into action. It causes the cell to divide continuously, even- tually producting a tumor. The micronuclei test was actually developed in the early 1970's, by a Canadian researcher at York Universi- ty, to examine micronuclei in human blood cells and bone ‘marrow. But Drs. Rosin, Stich and San recently pio- neered ihe test’s further ap- plication to sloughed-off cells from the inside of the mouth or other body parts. A common method of testing for cancer is to exam- ine tissue samples from the organs that might be af- fected. But this often re- quires surgery, hard to use aS a monitoring process for people who are exposed to carcinogens, say “in their work. INEXPENSIVE “We had to find some way of determining genetic damage in an individual which is noninvasive, quick and inexpensive,”’ says Dr. Rosin. Because the micronuclei test can be done on subjects repeatedly without harm, it is now regarded as the method of choice for surveys of large populations. “You take a target tissue and swab the inside of the mouth—we’ve focused on the mouth—to get cells. If you see elevated micronuclei, you know the person has been exposed to a_ car- cinogen, The more car- cinogen exposure in the mouth, the more micronuclei are produced and then, down the road, that’s where the cancer develops,’’ says Dr.Rosin. Dr. Rosin says the micronuclei test is best used in conjuction with test-tube and animal tests. For exam- ple, the micronuclei test will tell if someone has suffered carcinogen-induced genetic damage, but it won’t teil which carcinogen is the culprit. The other tests, however, will. By examining the type of bacteria that has survived, the analyst can determine the nature of the genetic damage and hence the carcinogen that caused it. So far, the researchers have used the micronuclei test in Southeast Asia and Indonesia to measure the ef- fects of widespread custom of chewing a quid of betel NEWS photo Torry Petors SNOW-COVERED cars iined up one morning this week to get onto the Second Narrows Bridge. Bad driving conditions meant commuters waited a little longer to get across the narrows. nut, usually with a bit of tobacco or lime. The prac- tice has resulted in the deaths of several hundred thousand people each year due to mouth cancers. EXAMINE CELLS Using the test, the resear- chers examined cells from scrapings of the mouth lin- ings of a group of people. They found micronuclei on about five per cent of the cells from those who chewed betel nuts, compared with 0.5 per cent of the cells of those who did not. The researchers are taking mouth cell samples from In- uit in a community where the cultural changes are just beginning. They will do so regularly, monitoring the numbers of micronuclei to try to determine how the In- uit’s changing dict affects their cancer risk. Although the test so far has been applied mostly. to cells from the mouth, it can, in fact, be done on sloughed-off cells from the esophagus, cervix, bladder (sloughed-off cells appear in urine), bronchi, stomach and colon. For example, the resear- chers have initiated a study to examine Pap smears col- lected over the !ast 15 years by family physicians for the B.C.’s Cancer Control Agency. By studying a series of cell samples, going back many years, from women who have since had cancer of the cervix, they will see if micronuclei preceded cer- vical cancer. They hope to be able to show that their technique. is a good predic- tive test. Keep Your Feet WARM & DRY Hickory Boots : Sd 9° reg. to $80 . Snow Joggers $2 j 99 to $35 ; Rear Entry Snow Bocts a 9? to $45 : N Extra < Special —— Mens Suede Lined gloves & mitts $549 apr. Shoe Factory Outlet 229 Mountain Hwy., N. Vancouver 986-6566 Fashion Frames or Contacts We have the image for you @ All eyeglass frames @ All soft contact lens CONTACT LENS CENTRE D) GImAGceE; 12-1242 Marine Drive Pemberton Plaza North Vancouver 984-3434 Also at: 403 North Rd. Coquitlam 936-1422 (daily wear & extended wear (Excluding special lens) Richmond 273-0371 4940 #3 Rd. 815 W. Hastings Vancouver 681-9488