“What you don’t understand is we didn’t know nothin’ about nothin’!” HBO is giving us a first look at The Immortal Life of Henrietta Lacks, its upcoming telepic featuring Oprah Winfrey in a rare starring turn. It’s the true story of the African-American woman whose cells were used to create the first immortal human cell line after many other such efforts failed — and without her permission or knowledge.

Told through the eyes of Henrietta Lacks’ daughter, Deborah (Winfrey), the HBO Films project chronicles her search, with the help of journalist Rebecca Skloot (Rose Byrne), to learn about the mother she never knew and understand how the unauthorized harvesting of Lacks’ cancerous cells in 1951 led to unprecedented breakthroughs that changed the face of medicine forever. When the sheepishly smiling writer tells Deborah that she wants to pen a book about her mom’s experience, Deborah looks her up and down, then says, “Hope I don’t regret this.”

Renée Elise Goldsberry, Rocky Carroll, Kyanna Simone Simpson, Courtney B. Vance, Leslie Uggams, Reg E. Cathey, Reed Birney, Ruben Santiago-Hudson, John Douglas Thompson, Adriane Lenox, Roger Robinson and Melvin Van Peebles co-star in the film from writer-director George C. Wolfe, based on Skloot’s 2010 book.

It premieres at 8 PM April 22 on HBO.