In chapter 27, "The Secret of Immortality," of the book The Immortal Life of Henrietta Lacks, author Rebecca Skloot informs us that a German virologist by the name of Harald zur Hausen discovered in 1983 the sexually transmitted virus strain called Human Papilloma Virus-16 (HPV-16). In 1984, he used the HeLa cell line to discover a brand new HPV strain he dubbed HPV-18, and he believed both HPV-16 and HPV-18 lead to cervical cancer. Skloot also reports that there are over 100 different strains of HPV although the National Cancer Institute (NCI) reports as of 2014 that we now know of over 200 different strains. Though HPV had been discovered by scientists as far back as 1956, Hausen particularly contributed to the research by connecting the HPV-16 and HPV-18 strains to cervical cancer, which then led to the HPV vaccine.
Through Hausen's research, using the HeLa cell line, scientists continued studying how HPV strains produce cancer. What they discovered is that "HPV inserts its DNA into the DNA of the host cell, where it produces proteins that lead to cancer" (p. 212). Scientists further discovered that "when they blocked the HPV DNA, cervical cancer cells stopped being cancerous," a discovery that led to Hausen creating the HPV vaccine and being honored with the Nobel Prize (p. 213).
The NCI explains the above in a more simplified manner by informing us that HPV contaminates epithelial cells that line the "inside and outside surfaces of the body" ("How Does high-risk HPV Cause Cancer?"). When HPV infiltrates one epithelial cell, the virus begins producing proteins that impede the epithelial cell from regularly controlling its own extreme cell growth, causing the cell to "grow in an uncontrolled manner" in the cell's attempt to remain alive ("How Does"). As the skin cell continues to grow uncontrollably, growth can create mutations in the cell's DNA that lead to even more excessive cell growth and a cancerous tumor.