Role of Immunosuppressive Microenvironment in Acquiring Immunotolerance Post-Photothermal Therapy

BACKGROUND: Nanoparticle-mediated photothermal therapy (PTT) has been well studied as a treatment for cancer. However, the therapeutic outcome of PTT is often hindered by the penetration depth of laser light. In the tumor margin beyond the laser penetration limit, tumor recurrence often occurs, bypassing the immune response of the host. Accumulating evidence suggests the prominent role of tumor microenvironment (TME) and its interactions with the immune components contribute to an immunosuppressive milieu during the post-therapy period. Here, we explored the immunosuppressive cascade generated after PTT, which is responsible for tumor recurrence, and identified the potential targets to achieve an effective PTT period. METHODS: Here, we investigated the immunosuppressive cascade generated after PTT in a CT26 tumor bearing mouse. The liposomal system loaded with the indocyanine green (ICG) was utilized for the generation of PTT with high efficiency. Immunological factors such as cytokines and protein expressions post-therapy were investigated through enzyme-linked immunosorbent assay, flow cytometry and western blot analysis. RESULTS: Our results suggested that PTT with ICG-loaded liposomes (Lipo-ICG) was effective for the first 5 days after treatment, resulting in tumor suppression. However, an immunosuppressive and pro-inflammatory environment developed thereafter, causing the recruitment and upregulation of the immune evasion factors of heat shock protein 70, programmed death ligand 1, indoleamine-dioxygenase, interleukin-6, transforming growth factor-β, regulatory T-cells, and myeloid-derived suppressor cells, to develop immunotolerance. CONCLUSION: Collectively, these findings have determined potential therapeutic targets to modulate the TME during PTT and achieve tumor ablation without remission.

Suppressive Effect of 19-nor-1alpha-25-Dihydroxyvitamin D2 on Gastric Cancer Cells and Peritoneal Metastasis Model

The active metabolite of vitamin D, 1,25-dihydroxyvitamin D3 (calcitriol), inhibits the growth of several types of human cancer cells in vitro, but its therapeutic use is limited because it causes hypercalcemia. Among its analogs, 19-nor-1,25-dihydroxyvitamin D2 (paricalcitol), has fewer calcemic effects and exhibits an activity equipotent to that of calcitriol. We assessed the antitumor and anti-inflammatory effects of paricalcitol in gastric cancer cells, and evaluated the potential role of vitamin D in the treatment of peritoneal metastatic gastric cancer. In this study, treatment with paricalcitol inhibited gastric cancer cell growth and induced cell cycle arrest. Paricalcitol also induced apoptosis and showed anti-inflammatory activity. Moreover, the growth of intraperitoneal metastases in vivo was reduced in mice treated with paricalcitol. 18F-FDG uptake was significantly lower in the paricalcitol group compared to control group (SUV; control group 13.2 +/- 5.3 vs paricalcitol group 4.5 +/- 3.0). Intraperitoneal tumor volume was significantly lower in paricalcitol treated mice (control group 353.2 +/- 22.9 mm3 vs paricalcitol group 252.0 +/- 8.4 mm3). These results suggest that the vitamin D analog, paricalcitol, has anticancer activity on gastric cancer cells by regulation of the cell cycle, apoptosis, and inflammation.

Induction of 90K-specific Cytotoxic T Lymphocytes for Colon Cancer Immunotherapy

BACKGROUND: Dendritic cell (DC)-based tumor vaccine is an attractive modality for the treatment of colon cancer because it has been recurred and produced few side effects in patients. Secretory glycoprotein 90K has been found at elevated level in various cancer tissues and sera. We investigated to establish a more effective DC vaccine for the treatment of colon cancer in which the levels of 90K are elevated. METHODS: We obtained the concentrated 90K from 293T cells stably expressing 90K. DCs were cultured from peripheral blood monocytes, and a DC vaccine pulsed with tumor lysate was compared with a DC vaccine pulsed with 90K. We measured the functional activity for CTLs by using IFN-gamma-enzyme linked immunoabsorbent spot (ELISPOT) assay. RESULTS: DCs pulsed with tumor lysate+90K exhibited the enhanced T cell stimulation, polarization of naive T cell toward Th1. The CTLs generated by DCs pulsed with 90K efficiently lysed HCT116 cells. The results indicate that 90K-speicifc-CTLs can recognize 90K proteins naturally presented by colon cancer cells. CONCLUSION: Our study suggests that 90K-specific CTLs generated by 90K-pulsed DCs could be useful effector cells for immunotherapy in colon cancer.