Cancer researchers at the University of Iowa say they’re making progress in following trails left by aggressive tumor cells — another step in trying to stop their deadly march. U-of-I research scientist Dr. Rich Seftor is lead author of the study.Dr. Seftor says they’re learning that aggressive or dangerous cancer cells change the chemical make-up of their surroundings using proteins produced by the cells called M-M-P’s. The aggressive cells produce a lot of the M-M-P’s and a building block found in the matrix, or area where the cells are found. If a way can be found to stop those building blocks from forming, it’s possible the cancer cells could be stopped. Seftor says even after the aggressive tumor cells have been killed, the area around them may have been changed too — for the worse.The study is being published as the cover story in the September 1 issue of the journal “Cancer Research.”