Natural killer (NK) cells play a pivotal role in host immunity against different malignancies, including pancreatic ductal adenocarcinoma (PDAC). Our study aimed to evaluate the antitumor effects of NK cell-based adoptive transfer immunotherapy for PDAC in an orthotopic mouse model. Orthotopic KrasLSL-G12D p53LSL-R172H Pdx1-Cre (KPC) mice were used to evaluate the therapeutic efficacy. Mouse NK cells (LNK cells) (1×106) were intravenously injected to tumor-bearing mice once a week for 3 weeks. MRI measurements (tumor volume and apparent diffusion coefficient (ADC) values) and survival were compared between control and LNK treated tumors. Flow cytometry and enzyme-linked immunosorbent assay (ELISA) were used to determine LNK cells cytotoxicity and IFN-γ level, respectively. LNK cells can produce a higher level of IFN-γ and more effectively lyse PDAC cells compared with spleen NK cells in vitro. LNK-cell adoptive transfer therapy elicited potent in vivo antitumor activity, resulting in delayed tumor growth (P=0.033) in KPC mice. The ADC values at the last timepoint ((0.94±0.06)×10-3 mm2/s) were significantly higher than that at first timepoint ((0.75±0.04)×10-3 mm2/s) in treated tumors (P<0.001). ADC values were significantly different between control group and treated tumors at the last time point ((0.75±0.09)×10-3 mm2/s vs (0.94±0.06)×10-3 mm2/s, P=0.004) in KPC mice. Our data demonstrate the potential of NK cell-based adoptive transfer immunotherapy for PDAC treatment.

As the major thermogenic tissue in body, the brown adipose tissue (BAT) was recently identified as an important factor to induce the rapid weight loss and malnutrition in malignancy. Current methods for detecting and quantifying brown adipose tissue (BAT) are in limited use. The aim of this study was to evaluate the changes of BAT tissue and its function in the development of pancreatic ductal adenocarcinoma (PDAC) by using magnetic resonance imaging (MRI). Ten-week-old female C57BL/6 mice were inoculated orthotopically with Pan02 tumor cells. R2* maps and two-point Dixon MRI were performed weekly for evaluation of BAT function and volume, respectively. The T2-weighted MRI was applied weekly for monitoring tumor growth. Meanwhile, the body weight was measured daily as another indication of malnutrition. The UCP1 levels in BAT and white adipose tissue (WAT) were assessed. The serum IL-6 was also measured as the biomarker of cancer-associated cachexia. T2-weighted MRI indicated the rapid tumor growth from week 3 to week 5 after tumor cell inoculation. The water-fat separated MRI could clearly identify and quantify the BAT. The function and volume of BAT could be monitored by weekly MRI measurement in tumor-bearing mice. The total body weights of PDAC tumor-bearing mice were relatively stable, however, was significantly lower than that of control C57BL/6 mice. The results of this study demonstrated the feasibility of detection and quantification of BAT in vivo by MRI during the development of pancreatic cancer.

The promise of dendritic cell (DC)-based immunotherapy has been established by two decades of translational research. However, long-term benefits of DC vaccination are reported in only scattered patients with pancreatic ductal adenocarcinoma (PDAC). Here we optimize DC vaccination and evaluate its safety and antitumor efficacy in the genetically engineered PDAC model (Kras^LSL-G12D p53^LSL-R172H Pdx-1-Cre (KPC mice)). KPC transgenic mice and orthotopic models using KPC cell lines were treated with DC vaccine via an intraperitoneal route. Tumor growth and microenvironment were dynamically monitored by magnetic resonance imaging (MRI). Histological analysis and flow cytometry were used to evaluate tumor-directed T cell immunity of these mice. DC vaccine via intraperitoneal injection suppressed tumor progression (P = 0.030) and significantly prolonged survival time (P = 0.028) in KPC mice. Vaccinated KPC mice displayed an increased antitumor T cell response indicated by a higher IFN-γ production (P = 0.016) and tumor-specific cytotoxicity (P = 0.027). Particularly, the mean apparent diffusion coefficient (ADC) values of KPC tumor calculated from diffusion weighted MRI (DW-MRI) were significantly higher in DC vaccine group than that in control group (P < 0.001). More interestingly, we observed that ADC positively correlated with fibrosis in KPC tumor (R² = 0.463, P = 0.015). Our study demonstrated that the immunization with our improved DC vaccine can elicit a strong tumor-specific immune response and tumor suppression in PDAC.