Gov. Charlie Baker and Boston Mayor Marty Walsh joined hundreds of other riders on the annual Pan-Mass Challenge bicycle ride to raise money for cancer research and treatment.The pair rode a 22-mile route from Wellesley to Foxborough on Sunday morning as part of the benefit for the Dana-Farber Cancer Institute.The full weekend ride ends at Provincetown on the tip of Cape Cod. The Pan-Mass Challenge hopes to raise $45 million this year.Walsh, who was successfully treated for cancer at Dana-Farber as a child, said he feels "a little emotional" about the event.Baker said he and his wife, Lauren Baker, borrowed bikes to join the ride in support of "a great cause."Former Massachusetts Senators John Kerry, now Secretary of State, and Scott Brown, have also taken part in the event in past years.