* The most heavily traded shares by volume were Great-West Lifeco GWO.TO, Sun Life Financial SLF.TO and Blackberry Ltd BB.TO. Updates prices, adds sector details May 27 (Reuters) - Canada's main stock index touched a record high on Thursday as better-than-expected quarterly profits from major lenders helped drive gains in most sectors, while shares of energy producers shrugged off a decline in oil prices. * Canada's trailblazing central bank is likely to cut its bond-buying program again this year, possibly as soon as July, as provinces ease curbs to contain the COVID-19 pandemic and inflation pressures build, analysts said.