Born in Brooklyn, Gore signed to Mercury Records as a teenager after being discovered by Quincy Jones. She had a No. 1 song at age 16 with "It's My Party," and subsequent songs included "You Don't Own Me," "Judy's Turn to Cry," and "Sunshine, Lollipops and Rainbows."
She was also nominated for an Academy Award in 1980 for "Out Here on My Own," which she co-wrote with her brother Michael for the movie Fame.
Gore also dabbled in acting, playing Catwoman's sidekick in TV's Batman, and also starring in Smokey Joe's Café on Broadway in the late 1990s. At the time of her death, she was working on a stage version of her life, the AP reports.
She came out as a lesbian by appearing as a host of PBS' LGBT-themed news magazine In the Life.
Gore is survived by Sasson, as well as her mother and brother.