Enhanced killing capacity of human Kupffer cells after activation with human granulocyte/macrophage-colony-stimulating factor and interferon gamma

Combination approaches to potentiate immune response after photodynamic therapy for cancer

Photodynamic therapy (PDT) has been used as a cancer therapy for forty years but has not advanced to a mainstream cancer treatment. Although it has been shown to be an efficient way to destroy local tumors by a combination of non-toxic dyes and harmless visible light, it is its additional effects in mediating the stimulation of the host immune system that gives PDT great potential to become more widely used. Although the stimulation of tumor-specific cytotoxic T-cells that can destroy distant tumor deposits after PDT has been reported in some animal models, it remains the exception rather than the rule. This realization has prompted several investigators to test various combination approaches that could potentiate the immune recognition of tumor antigens that have been released after PDT. This review will cover these combination approaches using immunostimulants including various microbial preparations that activate Toll-like receptors and other receptors for pathogen-associated molecular patterns, cytokines growth factors, and approaches that target regulatory T-cells. We believe that by understanding the methods employed by tumors to evade immune response and neutralizing them, more precise ways of potentiating PDT-induced immunity can be devised.

Efficacy of multiagent herpes simplex virus amplicon-mediated immunotherapy as adjuvant treatment for experimental hepatic cancer

OBJECTIVE

To evaluate the use of herpes simplex viral (HSV) amplicon vectors for production of tumor vaccines and to determine if such vaccines expressing combinations of immunostimulatory agents may be effective in the treatment of experimental liver cancer.

METHODS

A hepatic metastatic tumor model using CT-26 colorectal cancer in syngeneic Balb/C mice was utilized. Tumor vaccines were produced by brief (20 minutes) exposure of irradiated tumor cells to herpes amplicon vectors carrying the transgene for RANTES, B7.1, or GM-CSF. The antitumor efficacy of vaccination using tumor cells secreting GM-CSF (single agent) or a combination of RANTES/B7.1/GM-CSF (multiagent) was tested. The effect of 60% hepatectomy or T-cell depletion was also tested in this model.

RESULTS

In vitro assays confirmed high-level cytokine or costimulatory molecule production by cells transduced with amplicons. Antitumor efficacy was observed with single-agent or multiagent treatment. Without hepatectomy, immunization with single-agent or multiagent vaccine therapy appears equivalent. When administered in the setting of hepatectomy, multiagent regimens produced a higher cure rate than single-agent therapy (50% vs. 12.5%, =.03). Animals treated with GM-CSF alone had an average nodule count of 40 +/- 19 ( <.006 vs. Hep control 232 +/- 30), while animals treated with multiagent therapy had an average nodule count of 11 +/- 7 ( <.0004 vs. control). CD4 and CD8 lymphocyte blockade abrogated observed efficacy, confirming a lymphocyte-mediated response.

CONCLUSIONS

Tumor vaccines produced using HSV amplicon-mediated gene transfer may be useful in the treatment of liver malignancies. In the setting of hepatectomy, multiagent vaccine therapy offers an advantage over single-agent therapy. These data encourage consideration of such HSV-based neoadjuvant immunotherapy for treatment of liver malignancies.

Laparotomy, laparoscopy, cancer, and beyond

The fate of laparoscopic methods for the treatment of cancer remains uncertain. Published middle-range oncologic results from nonrandomized studies demonstrate that laparoscopic methods are associated with an outcome comparable with results after open resection. The world awaits the 3- and 5-year oncologic results of the ongoing randomized and prospective trials. There is a possibility that laparoscopic methods may be associated with a survival benefit. Port tumors remain a concern. However, results at this writing suggest that these recurrences take place at a frequency similar to that of incisional recurrences following open cancer resection. Port tumors currently are viewed as local recurrences. Traumatization of the tumor at the time of resection is thought to be the most important surgery-related risk factor. The demonstration of a survival benefit in a randomized trial would likely have a tremendous impact on the surgical world. Avoidance of laparotomy-related immunosuppression and tumor stimulation, both of which have been well demonstrated in animal studies, theoretically, might account for differences in cancer outcome. The early postoperative period may be a critical time during which the fate of many cancer patients is determined. It is possible that this may be an ideal time frame for antitumor immunotherapy because the tumor burden is at its lowest, and because immunotherapy, unlike conventional chemotherapy, is unlikely to have a negative impact on wound and anastomotic healing. Perioperative nonspecific upregulation of immune function via pharmacologic means may improve long-term oncologic results. Similarly, preoperative tumor vaccines might provide patients with a specific means of combating any remaining tumor cells after curative resection. The results of several recently completed murine studies support both of these ideas. Finally, early postoperative administration of monoclonal antitumor antibodies might provide patients with specific means of combating any remaining tumor cells after curative resection. The introduction of advanced minimally invasive techniques nearly a decade ago has led to new methods of approaching malignant tumors that have the potential to have an impact on the oncologic outcome of cancer patients. This decade-long journey also has led to new insights regarding the impact of surgery on the patient. It also has alerted us concerning the importance of the immediate postoperative period in the patient's ongoing struggle against the tumor. These insights hopefully will lead to better surgical methods and new perioperative adjuvant therapies that will increase the rate of survival and reduce the recurrence rates for cancer patients.

Prevention of hepatic tumor metastases in rats with herpes viral vaccines and gamma-interferon

Previous studies showed that gammaIFN decreases metastatic hepatic tumor growth by stimulating Kupffer cells (KC). The present studies examine whether lymphocyte stimulation via cells engineered to secrete GM-CSF or IL-2 decreases hepatic tumor growth, and whether stimulation of both macrophages and lymphocytes is more effective than either individually. Rats were immunized with irradiated hepatoma cells transduced by herpes viral amplicon vectors containing the genes for GM-CSF, IL-2 or LacZ. On day 18, half of each group was treated with 5 x 10(4) U gammaIFN, or saline intraperitoneally for 3 d. On day 21, all rats received 5 x 10(5) hepatoma cells intrasplenically. On day 41, rats were killed and tumor nodules were counted. Separate rats underwent splenocyte and KC harvest for assessment of lymphocyte- and macrophage-mediated tumor cell kill in vitro. GM-CSF or IL-2 vaccines or gammaIFN decreased tumor nodules significantly (GM-CSF 13+/-4, IL-2 14+/-6 vs. control 75+/-24, P < 0.001). Combination therapy was more effective, and completely eliminated tumor in 4 of 12 IFN-GM-CSF and 8 of 11 IFN-IL-2 animals. Additional rats underwent partial hepatectomy, an immunosuppressive procedure known to accelerate the growth of hepatic tumor, following tumor challenge. Therapy was equally effective in this immunosuppressive setting. Vaccination is associated with enhancement of splenocyte-mediated tumoricidal activity, whereas the effect of gammaIFN is mediated by KC. GM-CSF and IL-2 vaccine therapy and pretreatment with gammaIFN represent effective strategies in reducing hepatic tumor. Combination therapy targets both lymphocytes and macrophages, and is more effective in reducing tumor than either therapy alone.