Final answer:
Human cell lines can be transformed into oncogenic lines with the introduction of SV40 T antigen, ras-V12, and hTERT (telomerase), leading to uncontrolled cell growth and tumorigenesis by interfering with normal cell regulation and extending cellular lifespan.
Step-by-step explanation:
In human cell lines, normal tissue types can be transformed into oncogenic lines by the introduction of SV40 T antigen, ras-V12, and hTERT (telomerase). Oncogenic viruses like SV40 have the ability to cause cancer by interfering with normal cell regulation or by introducing genes that stimulate unregulated cell growth, known as oncogenes. Some of these viruses are DNA viruses, which bind factors such as the large T antigen to proteins like p53, disabling the cell's growth checkpoint controls and leading to uncontrolled division and tumorigenesis. Furthermore, the transformation of a normal cell into a cancer cell involves accumulated genetic damage to proto-oncogenes and tumor-suppressor genes.
Ras proteins are also involved in cell line transformation, where the oncogenic form ras-V12 can contribute to uncontrolled cellular proliferation. Additionally, the enzyme telomerase, encoded by hTERT, is implicated in cellular immortality, a characteristic of cancer cells. Telomerase adds telomeric repeats to the ends of chromosomes, preventing them from becoming critically short and allowing the cell to evade senescence and continue dividing indefinitely, which aids the transformation of normal cells into cancer cells.