PD-L1 status may be a good predictor of prognosis in HCC patients with high HLA class I expression. Novel therapies targeting the PD-L1/PD-1 pathway may improve the prognosis of patients with HCC.

Several chemotherapeutic drugs have immune-modulating effects. For example, cyclophosphamide (CP) and gemcitabine (GEM) diminish immunosuppression by regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), respectively. Here, we show that intermittent (metronomic) chemotherapy with low-dose CP plus GEM can induce anti-tumor T cell immunity in CT26 colon carcinoma-bearing mice. Although no significant growth suppression was observed by injections of CP (100 mg/kg) at 8-day intervals or those of CP (50 mg/kg) at 4-day intervals, CP injection (100 mg/kg) increased the frequency of tumor peptide-specific T lymphocytes in draining lymph nodes, which was abolished by two injections of CP (50 mg/kg) at a 4-day interval. Alternatively, injection of GEM (50 mg/kg) was superior to that of GEM (100 mg/kg) in suppressing tumor growth in vivo, despite the smaller dose. When CT26-bearing mice were treated with low-dose (50 mg/kg) CP plus (50 mg/kg) GEM at 8-day intervals, tumor growth was suppressed without impairing T cell function; the effect was mainly T cell dependent. The metronomic combination chemotherapy cured one-third of CT26-bearing mice that acquired tumor-specific T cell immunity. The combination therapy decreased Foxp3 and arginase-1 mRNA levels but increased IFN-γ mRNA expression in tumor tissues. The percentages of tumor-infiltrating CD45(+) cells, especially Gr-1(high) CD11b(+) MDSCs, were decreased. These results indicate that metronomic chemotherapy with low-dose CP plus GEM is a promising protocol to mitigate totally Treg- and MDSC-mediated immunosuppression and elicit anti-tumor T cell immunity in vivo.

Docetaxel (DTX) is a useful chemotherapeutic drug for the treatment of hormone-refractory prostate cancer. However, emergence of DTX resistance has been a therapeutic hurdle. In this study, we investigated the effect of combining DTX with Bcl-2 family inhibitors using human prostate cancer cell lines (PC3, LNCaP, and DU145 cells). PC3 cells were less sensitive to DTX than were the other two cell lines. In contrast to ABT-199, which inhibits Bcl-2 and Bcl-w, both ABT-263 and ABT-737, which inhibit Bcl-2, Bcl-xL, and Bcl-w, significantly augmented the antitumor effect of DTX on PC3 cells. ABT-263 also enhanced the antitumor effect of DTX on a DTX-resistant PC3 variant cell line. The antitumor effect of ABT-263 was due mainly to its inhibitory effect on Bcl-xL. In a xenograft mouse model, DTX and ABT-737 combination therapy significantly inhibited PC3 tumor growth. Interestingly, although ABT-263 activated caspase-9 in PC3 cells, inhibition of caspase-9 unexpectedly promoted ABT-263-induced apoptosis in a caspase- 8-dependent manner. This augmented apoptosis was also observed in LNCaP cells. These findings indicate that Bcl-xL inhibition can sensitize DTX-resistant prostate cancer cells to DTX, and they reveal a unique apoptotic pathway in which antagonism of Bcl-2 family members in caspase-9-inhibited prostate cancer cells triggers caspase-8-dependent apoptosis.

These results might encourage the further evaluation of the combination of peptide vaccination and a low dose of estramustine phosphate for HLA-A24+ HRPC patients.

Two different trials of peptide vaccination were conducted for patients with recurrent gynecologic cancers. In the first regimen, four HLA-A24+ patients (two with cervical cancer and two with ovarian cancer) were vaccinated with peptides that were predesignated before vaccination. Three patients exhibited with a grade 1 adverse effect, and no clinical response was observed in any patients. In the second regimen, six HLA-A24+ and four HLA-A2+ patients (five with cervical cancer, one with endometrial cancer, one with uterine sarcoma, and three with ovarian cancer) were vaccinated with peptides (maximum four) to which preexisting cytotoxic T lymphocyte precursors in the periphery were confirmed before vaccination. With this regimen, grade 1 adverse effects were observed in eight patients, a grade 2 adverse effect in one patient, and a grade 3 adverse effect (ie, rectal bleeding) in one patient. However, this regimen was able to enhance peptide-specific cytotoxic T lymphocytes in seven of ten patients, and three of five cervical cancer patients showed objective tumor regression. Analysis of immunoglobulin G -reactive to administered peptides suggested that the induction of peptide-specific immunoglobulin G was correlated with clinical responses. Overall, these results suggest that peptide vaccination of patients showing evidence of preexisting peptide-specific cytotoxic T lymphocyte precursors could be superior to vaccination with predesignated peptides, and that the evidence-based regimen is applicable for clinical trials in treatment of patients with recurrent gynecologic cancers.