The properties of tumor-initiating cells from a hepatocellular carcinoma patient's primary and recurrent tumor

Hepatocellular carcinoma (HCC) is associated with a high morbidity and mortality due to its high rate of recurrence. However, little is known about the biological characteristics of recurrent HCC cells. A single patient's primary and recurrent HCC-derived cell lines, Hep-11 and Hep-12, respectively, were established by primary culture. These two cell lines have the same hepatitis B virus integration site and share many common amplifications and deletions, which suggest that they have the same clonal origin. While Hep-11 cells were non-tumorigenic at 16 weeks following injection of up to 10 000 cells, injection of only 100 Hep-12 cells was sufficient to initiate tumor growth, and all single Hep-12 clones were tumorigenic in immunodeficient mice. Compared with Hep-11, Hep-12 cells expressed the oval cell markers AFP, NCAM/CD56, c-kit/CD117, as well as multiple stem cell markers such as Nanog, OCT4 and SOX2. In addition, >90% of Hep-12 cells were aldehyde dehydrogenase positive. They were also less resistant to paclitaxel, but more resistant to doxorubicin, cisplatin and hydroxycamptothecin (HCPT), which had been administrated to the patient. Furthermore, Hep-12 cells expressed higher levels of poly (adenosine diphosphate-ribose) polymerase-1 (PARP-1) than Hep-11, and PARP-1 inhibition potentiated the sensitivity to HCPT in Hep-12 cells but not in Hep-11 cells. These results indicate that a large population of the recurrent HCC-derived Hep-12 cells were tumor-initiating cells and that elevated expression of PARP-1 was related to their resistance to HCPT.