This study characterized cancer stem cells (CSCs) in hepatocellular carcinoma (HCC) cell lines, tumor specimens, and blood samples. The CD90+ cells, but not the CD90(-) cells, from HCC cell lines displayed tumorigenic capacity. All the tumor specimens and 91.6% of blood samples from liver cancer patients bore the CD45(-)CD90+ population, which could generate tumor nodules in immunodeficient mice. The CD90+CD44+ cells demonstrated a more aggressive phenotype than the CD90+CD44(-) counterpart and formed metastatic lesions in the lung of immunodeficient mice. CD44 blockade prevented the formation of local and metastatic tumor nodules by the CD90+ cells. Differential gene expression profiles were identified in the CD45(-)CD90+ and CD45(-)CD90(-) cells isolated from tissue and blood samples from liver cancer patients and controls.

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We have investigated whether both primary CD8 T cell activation and CD8 T cell-mediated protection from Mycobacterium tuberculosis challenge could occur in mycobacterial-vaccinated CD4 T cell-deficient (CD4KO) mice. Different from wild-type C57BL/6 mice, s.c. vaccination with bacillus Calmette-Guérin (BCG) in CD4KO mice failed to provide protection from secondary M. tuberculosis challenge at 3 wk postvaccination. However, similar to C57BL/6 mice, CD4KO mice were well protected from M. tuberculosis at weeks 6 and 12 postvaccination. This protection was mediated by CD8 T cells. The maintenance of protective effector/memory CD8 T cells in CD4KO mice did not require the continuous presence of live BCG vaccine. As in C57BL/6 mice, similar levels of primary activation of CD8 T cells in CD4KO mice occurred in the draining lymph nodes at 3 wk after BCG vaccination, but different from C57BL/6 mice, the distribution of these cells to the spleen and lungs of CD4KO mice was delayed, which coincided with delayed acquisition of protection in CD4KO mice. Our results suggest that both the primary and secondary activation of CD8 T cells is CD4 T cell independent and that the maintenance of these CD8 T cells is also independent of CD4 T cells and no longer requires the presence of live mycobacteria. However, the lack of CD4 T cells may result in delayed distribution of activated CD8 T cells from draining lymph nodes to distant organs and consequently a delayed acquisition of immune protection. Our findings hold implications in rational design of tuberculosis vaccination strategies for humans with impaired CD4 T cell function.

Gamma interferon (IFN-␥) is a key cytokine in host defense against intracellular mycobacterial infection. It has been believed that both CD4 and CD8 T cells are the primary sources of IFN-␥. However, the relative contributions of CD4 and CD8 T-cell subsets to IFN-␥ production and the relationship between CD4 and CD8 T-cell activation have not been examined. By using a model of pulmonary mycobacterial infection and various immunodetection assays, we found that CD4 T cells mounted a much stronger IFN-␥ response than CD8 T cells at various times after mycobacterial infection, and this pronounced IFN-␥ production by CD4 T cells was attributed to both greater numbers of antigen-specific CD4 T cells and a greater IFN-␥ secretion capacity of these cells. By using major histocompatibility complex class IIdeficient or CD4-deficient mice, we found that the lack of CD4 T cells did not negatively affect primary or secondary CD8 T-cell IFN-␥ responses. The CD8 T cells activated in the absence of CD4 T cells were capable of immune protection against secondary mycobacterial challenge. Our results suggest that, whereas both CD4 and CD8 T cells are capable of IFN-␥ production, the former represent a much greater cellular source of IFN-␥. Moreover, during mycobacterial infection, CD8 T-cell IFN-␥ responses and activation are independent of CD4 T-cell activation.The type 1 T-cell-mediated immune response is essential to host defense against intracellular mycobacterial infection. Indeed, hosts deficient in both CD4 and CD8 T cells readily succumb to mycobacterial infection (9,13,26,28). Although CD4 T cells are traditionally believed to play a major protective role, the CD4 and CD8 T-cell subsets have each been found to be able to confer immune protection (4,5,20,21,25,26), and a lack of CD8 T cells results in weakened host defense against mycobacterial infection (9,13,26). Gamma interferon (IFN-␥) plays a critical role in T-cell immunity via its potent activating effects on Mycobacterium-infected macrophages and granuloma formation (2,27,28). Although T cells, NK cells, and macrophages are all able to produce IFN-␥ (6, 24), CD4 and CD8 T cells are considered to be the primary sources of this cytokine during mycobacterial infection (20,25,26,29). Recent evidence suggests that IFN-␥, but not cytotoxic activity, is required for antimycobacterial immune protection mediated by CD8 T cells (3,11,20). However, the relative contribution of CD4 and CD8 T-cell subsets to IFN-␥ responses during mycobacterial infection has remained largely to be determined. More specifically, it remains to be determined whether CD4 and CD8 T cells produce differential quantities of IFN-␥ and, if so, whether such differential IFN-␥ production is attributed to differential frequencies of antigen-specific T-cell subsets, differential IFN-␥ secretion capacities, or both. Furthermore, it also is not yet completely understood whether CD4 and CD8 T cells are dependent on one another for their activation and IFN-␥ responses during mycobacterial infection. Further und...

The present study investigated the effect of YC-1, a novel anti-cancer agent, on the chemo-sensitivity of hepatocellular carcinoma (HCC). YC-1 was administered with chemo-cytotoxic drug, cisplatin, both in vitro and in vivo. YC-1 alone downregulated the expression of phosphorylated form of signal transducers and activators of transcription 3 (P-Stat3[705]), a key mediator in chemo-resistance. When combined with cisplatin, YC-1 further promoted tumor cell apoptosis, decreased the expression of P-Stat3(705), Bcl-xL, CyclinD1 and survivin, and induced the cleavage of caspase 9 and PARP. Overexpression of Stat3 reversed YC-1 induced cell death. YC-1 inhibited Stat3 activity by enhancing the polyubiquitination of P-Stat3(705) induced by cisplatin. In the in vivo setting, YC-1 combined with cisplatin remarkably suppressed tumor growth in a HCC xenograft model, and this effect was also accompanied by YC-1 mediated downregulation of P-Stat3(705), Bcl-xL, Cyclin D1 and survivin, and induction of cleaved caspase 9 and PARP in the tumor tissues. In conclusion, the present study demonstrated a novel anti-cancer effect of YC-1 in enhancing chemo-sensitivity of HCC cells to cisplatin through a Stat3 dependent manner. This finding provides insight into design of a new therapeutic strategy to improve efficacy of chemotherapy in HCC patients.