BOSTON (AP) -The Boston Marathon is breaking with a 112-year tradition, putting corporate ads on the start and finish lines to help its two main sponsors extract more value from ties with the world's oldest marathon.

Race organizers also announced Tuesday that they were increasing its purse by more than 38 percent, from $575,000 to $796,000, making it the richest of the World Marathon Majors events.

The changes in sponsorship ads highlight distance running's growing dependence on sponsors to provide lucrative prize money to attract leading athletes and raise its profile, said Guy Morse, executive director of the Boston Athletic Association, the race's organizer.

They also demonstrate the need for support to meet operating expenses and make donations to the eight cities and towns that provide public safety and other services to runners passing along the marathon's 26.2-mile route, Morse said.