Virginia Slims sponsored women's tennis beginning in 1970. Initially it was a rival tour to the USLTA, which was both men and women (with the women earning A LOT LESS). Most of the top names, spearheaded by Billie Jean King, signed on to play the tour for 1 dollar. Maragret Court, Wade, Evert and Goolagong didn't play the Slims until a few years later...although Chris inexplicably won the Slims season ending championship the first few years (yet she played for the rival tour?). Gladys Hellman, publisher of WorldTennis and mother of top tenner Julie, was also quite instrumental in the formation of the Slims tour.
Virginia Slims was a new cigarette for the 'independant' woman of the early 70's and it was considered great marketing to couple it with the ever expanding popularity of women's pro tennis. I think it took people a while to put the whole lung cancer/athletics marriage part together. Then it quit making sense.