Prospects and challenges of anticancer agents' delivery via chitosan-based drug carriers to combat breast cancer: a review.

Breast cancer (BC) is considered as one the most prevalent cancers worldwide. Due to its high resistance to chemotherapy and high probability of metastasis, BC is one of the leading causes of cancer-related deaths. The controlled release of chemotherapy drugs to the precise site of the tumor tissue will increase the therapeutic efficacy and decrease side effects of systemic administration. Among various drug delivery systems, natural polymers-based drug carriers have gained significant attention for cancer therapy. Chitosan, a natural polymer obtained by de-acetylation of chitin, holds huge potential for drug delivery applications because chitosan is non-toxic, non-immunogenic, biocompatible, chemically modifiable, and can be processed to form various formulations. In the current review, we will discuss the prospects and challenges of chitosan-based drug delivery systems in treating BC.

The anti-tumor effect and increased tregs infiltration mediated by rAAV-SLC vector.

To explore the anti-tumor effect and immune mechanism mediated by a new recombinant adeno-associated virus (rAAV) encoding secondary lymphoid tissue chemokine (SLC) mature peptide gene. AAV Helper-Free system was used for rAAV-SLC package. The anti-tumor effect of SLC was detected by bearing tumor established from Hepal-6 cells both in C57BL/6J and nude mice. Flow cytometry analysis and IHC for Tumor-infiltrating T cells and CD11c+DCs were also investigated to explore the immunological mechanism. rAAV-SLC was successfully packaged in AAV293 cells and transfected Hepal-6 tumor cells at high efficiency. The anti-tumor effect was demonstrated by less tumor weight and longer survival outcome. Coincident with the anti-tumor response, local elaboration of SLC within the tumor bed elicited a heavy infiltration of CD4+, CD8+T cells and CD11c+ dendritic cells into the tumor sites. More importantly, there was higher infiltration of Foxp3+ regulatory T cells (Tregs). Local elaboration of SLC mediated by rAAV-SLC has strong T cell mediated anti-tumor effect. The study also suggested that Tregs in the tumor microenvironment tampered the anti-tumor effect.

Depletion of CD4+ CD25+ regulatory T cells promotes CCL21-mediated antitumor immunity.

CCL21 is known to attract dendritic cells (DCs) and T cells that may reverse tumor-mediated immune suppression. The massive infiltration of tumors by regulatory T cells (Tregs) prevents the development of a successful helper immune response. In this study, we investigated whether elimination of CD4(+) CD25(+) Tregs in the tumor microenvironment using anti-CD25 monoclonal antibodies (mAbs) was capable of enhancing CCL21-mediated antitumor immunity in a mouse hepatocellular carcinoma (HCC) model. We found that CCL21 in combination with anti-CD25 mAbs (PC61) resulted in improved antitumor efficacy and prolonged survival, not only inhibited tumor angiogenesis and cell proliferation, but also led to significant increases in the frequency of CD4(+), CD8(+) T cells and CD11c(+) DCs within the tumor, coincident with marked induction of tumor-specific CD8(+) cytotoxic T lymphocytes (CTLs) at the local tumor site. The intratumoral immune responses were accompanied by the enhanced elaboration of IL-12 and IFN-γ, but reduced release of the immunosuppressive mediators IL-10 and TGF-ß1. The results indicated that depletion of Tregs in the tumor microenvironment could enhance CCL21-mediated antitumor immunity, and CCL21 combined with anti-CD25 mAbs may be a more effective immunotherapy to promote tumor rejection.

CCR7 expression and intratumoral FOXP3+ regulatory T cells are correlated with overall survival and lymph node metastasis in gastric cancer.

The aim of this study was to investigate the prognostic value of chemokine receptor CCR7 expression and intratumoral FOXP3(+) regulatory T cells (Tregs) in gastric cancer. CCR7(+) tumor cells and FOXP3(+) Tregs were assessed by immunohistochemistry in tissue microarrays containing gastric cancer from 133 patients. Prognostic effects of low or high CCR7 and FOXP3 expression were evaluated by Cox regression and Kaplan-Meier analysis, as well as the correlation between CCR7 positive score and intratumoral FOXP3(+) cell number in a longitudinal assessment. The analysis showed that the high expression levels of CCR7 and FOXP3 were detected in 69.9% and 65.4% of cases, respectively. High CCR7 expression in gastric cancer cells was significantly associated with poor overall survival (OS) (P = 0.010) and lymph node metastasis (P = 0.009), and was an independent factor for worse OS (P = 0.023) by multivariate analysis. High numbers of intratumoral FOXP3(+) Tregs significantly correlated with shorter OS (P = 0.021) and lymph node metastasis (P = 0.024), and was also an independent factor for adverse OS (P = 0.035). Furthermore, there was a significantly positive correlation between CCR7 positive score and intratumoral FOXP3(+) cell number (r = 0.949, P<0.001). These results revealed that CCR7 expression in gastric cancer cells and intratumoral FOXP3(+) Tregs could be considered as a co-indicator of clinical prognosis of gastric cancer.

Higher intratumoral infiltrated Foxp3+ Treg numbers and Foxp3+/CD8+ ratio are associated with adverse prognosis in resectable gastric cancer.

PURPOSE: The aim of the present study was to investigate the prognostic value of tumor-infiltrated lymphocytes (TILs), especially the prognostic value of Foxp3+ regulatory T cells (Tregs), CD8+ CTLs and Tregs/CD8+ ratios in gastric cancer patients after R0 resection. PATIENTS AND METHODS: From 133 patients, CD4+, CD8+ and Foxp3+ TILs were assessed by immunohistochemistry in tissue microarrays and N1 regional lymph nodes sections containing gastric cancer. The prognostic effects of low- or high-density TIL subsets were evaluated by Cox regression and Kaplan-Meier analysis using median values as cutoff, while the effects of Foxp3+/CD8+ ratios were evaluated using the value determined by ROC cure analysis as cutoff. RESULTS: It was found that CD4+ and CD8+ TILs were not associated with overall survival (OS). In the tumor sites, higher Foxp3+ Tregs/CD8+ ratio was an independent factor for worse OS (multivariate analysis HR = 2.827, P = 0.037). The 1-year, 2-year and 3-year OS rates were 90, 77.5 and 70% for the group with intratumoral high Tregs/CD8+ ratio, compared with 100, 94.3 and 90.5% for the group with intratumoral low ratio. At the same time, the presence of intratumoral high Foxp3+ Tregs was also associated with worse OS (log rank test, P = 0.025); however, it was not an independent predictor and correlated with intratumoral Foxp3+ Tregs/CD8+ ratio (chi(2) test, P < 0.001). Although the infiltration of Foxp3+ Tregs in N1 regional lymph nodes was associated with lymph node metastasis (P = 0.028), it was not associated with prognosis (P = 0.458). CONCLUSIONS: Intratumoral high Foxp3+ Tregs/CD8+ ratio was an independent predictor for the prognosis of gastric cancer. It can be inferred that a combination of deletion of Tregs and stimulation of CD8+ effector T cells may be an effective immunotherapy to prolong survival after surgery.

SLC/CCR7 stimulates the proliferation of BMDCs by the pNF-kappaB p65 pathway.

The chemokine receptor CCR7 is highly expressed in dendritic cells (DCs), T cells, and other immune effector cells. One of the high-affinity ligand that can bind to CCR7 is the secondary lymphoid tissue chemokine (SLC). The SLC/CCR7 axis plays an important role in the immune system by inducing the chemotaxis and migration of immune effector cells. In this study, we examined the effect of SLC at different concentrations (0, 50, 100, 200, 300, and 400 ng/mL) on the proliferation of bone-marrow-derived dendritic cells (BMDCs). ELC (CCL19), another high-affinity ligand for CCR7, was used as the control at the same time. We found that SLC directly stimulated the proliferation of BMDCs and enhanced the antigen-presenting function and CCR7 expression. Western blot analysis showed that pNF-kappaBp65 was involved in this mechanism. We also found that the NF-kappaB inhibitor PDTC could specifically block the proliferation and CCR7 expression of BMDCs induced by SLC or ELC (200 ng/mL). The results suggested that there were cross-talk signals between the chemotaxis and proliferation of BMDCs involving the SLC/CCR7 axis.

More than chemotaxis: a new anti-tumor DC vaccine modified by rAAV2-SLC.

Secondary lymphoid tissue chemokine (SLC) is strongly expressed in secondary lymphoid organs. Its ability to facilitate chemotaxis of both dendritic cells (DC) and T cells makes it a promising candidate for cancer therapy. In this study, we modified a BMDC vaccine by incorporating the SLC mature peptide gene. The efficacy of this vaccine was evaluated using a mouse hepatocellular carcinoma (HCC) model, with rAAV2 as the gene delivery vector. The rAAV2 encoding SLC (rAAV2-SLC) transfected immature BMDCs at high efficiency and the anti-tumor effects of SLC gene modified BMDCs (rAAV2-SLC/BMDC) were evaluated. In addition, rAAV2-SLC/BMDC vaccine injected directly into tumors attracted more CD4(+) and CD8(+) T lymphocytes into tumors and showed stronger anti-tumor effects than footpad delivery. Moreover, we found that the phenotypic expression of MHC II, the secretion of IL-12 and IFN-gamma, and T cell stimulation were increased in vitro following treatment with rAAV2-SLC/BMDC vaccine and these responses were inhibited by PTX. In vivo, PTX also inhibited the anti-tumor effects of the vaccine. The results suggest that the expression of SLC by rAAV2-SLC/BMDC plays more than a chemotactic role in anti-tumor responses, thus these studies further demonstrate that SLC has potential to be valuable in cancer therapy.