Jellybean is a spirited 4-year-old Labrador Retriever mix who is considered a rock star among the dozens of dogs enrolled in cutting-edge cancer research at Tufts University’s Cummings School of Veterinary Medicine.“When we have a better understanding of why some dogs [like Jellybean] do well and others don’t, it’s going to allow us to layer on additional treatments to enhance the response that we’ve seen,” said Dr. Cheryl London, the Cummings School’s associate dean of research and graduate education who oversees clinical trials.For more than two years now, the Mendoncas have driven more than an hour from their North Kingstown, R.I., home to the Cummings School in Grafton each month so researchers can track Jellybean’s progress and take X-rays and blood samples.Instead of enrolling dogs like Jellybean, who had had amputations and then failed chemotherapy, they are now enrolling dogs with bone cancers that have not yet spread and giving them the triple-drug combination for two weeks before amputation.Similar to the listeria treatment, the three-drug therapy still given to Jellybean has produced few side effects other than to turn her once-jet black and tan fur predominantly gray."