Induction of protective immunity to RM-1 prostate cancer cells with ALVAC-IL-2/IL-12/TNF-α combination therapy

Immunogenic Material Vaccine for Cancer Immunotherapy by Structure-Dependent Immune Cell Trafficking and Modulation

Inherently immunogenic materials offer enormous prospects in enhancing vaccine efficacy. However, the understanding and improving material adjuvanticity remain elusive. Herein how the structural presentation of immunopotentiators in a material governs the dynamic dialogue between innate and adaptive immunity for enhanced cancer vaccination is reported. The immunopotentiator manganese into six differing structures that resemble the architectures of two types of pathogens (spherical viruses or rod-like bacteria) is precisely manipulated. The results reveal that innate immune cells accurately sense and respond to the architectures, of which two outperformed material candidates (151 nm hollow spheres and hollow microrods with an aspect ratio of 4.5) show higher competence in creating local proinflammatory environment with promoted innate immune cell influx and stimulation on dendritic cells (DCs). In combination with viral peptides, model proteins, or cell lysate antigens, the outperformed microrod material remarkably primes antigen-specific CD8 cytolytic T cells. In prophylactic and therapeutic regimens, the microrod adjuvanted vaccines display optimal aptitude in tumor suppression in four aggressive murine tumor models, by promoting the infiltration of heterogeneous cytolytic effector cells while decreasing suppressive immunoregulatory populations in tumors. This study demonstrates that a rationally selected architecture of immunogenic materials potentially advances the clinical reality of cancer vaccination.

Normal Basal Epithelial Cells Stimulate the Migration and Invasion of Prostate Cancer Cell RM-1 by TGF-β1/STAT3 Axis in vitro

Aim

Basal epithelial cells are absent in distant prostate cancer. This study aimed to investigate whether basal epithelial cells could suppress migration and invasion of prostate cancer cells to become a new treatment strategy for prostate cancer.

Main Methods

Basal epithelial cells were identified by immunofluorescence with anti-p63. Wound healing assays or transwell assays were used to explore the effects of basal epithelial cells, TGF-β1, SB431542 (inhibitor of TGF-β type I receptor) or stattic (inhibitor of phosphorylated STAT3) on migration or invasion of mouse prostate cancer cell (RM-1). Concentration of TGF-β1 was measured by ELISA assay. HE staining was used to investigate cell morphology. Immunocytochemistry with anti-p63 was used to identify basal epithelial cells. Levels of STAT3, p-STAT3 (Ser727) and proteins associated with EMT were measured with Western blot assay. Cell proliferation was measured with MTT or CCK8 assay.

Results

Normal basal epithelial cells acquired from mouse prostate were specific to anti-p63 and more than 90%. Basal epithelial cells and RM-1 could both secrete TGF-β1. Basal epithelial cells and TGF-β1 promoted the migration and invasion of RM-1 through changing the cell morphology and up-regulating expression of ZEB1, N-cadherin, vimentin, snail and p-STAT3 (Ser727), at the same time down-regulating E-cadherin of RM-1. SB431542 strongly suppressed migration, invasion as well as the expressions of EMT relevant proteins and p-STAT3 (Ser727) of co-cultured RM-1. In addition, stattic suppressed proliferation, migration and invasion of non-treated RM-1 and co-cultured RM-1.

Conclusion

Our study suggests that normal basal epithelial cells might stimulate the migration and invasion of RM-1 by TGF-β1/STAT3 axis which could be suppressed by inhibitor of TGF-β receptor and inhibitor of p-STAT3. So, basal epithelial cells might not become a treatment strategy for prostate cancer, but our results could provide some researching references for other diseases which include basal epithelial cells such as prostatic intraepithelial neoplasia, prostatic hyperplasia, cervical cancer, or urinary bladder cancer.

Inhibition of STAT3 augments antitumor efficacy of anti-CTLA-4 treatment against prostate cancer

There is an urgent need for new treatment options in metastatic drug-resistant prostate cancer. Combining immunotherapy with other targeted therapies may be an effective strategy for advanced prostate cancer. In the present study, we sought to investigate to enhance the efficacy of anti-CTLA-4 therapy against prostate cancer by the combination with STAT3 inhibition.

Male C57BL6 mice were subcutaneously inoculated with the murine prostate cancer cell line RM-1. Tumor progression was monitored following treatment with vehicle, the small molecule STAT3 inhibitor GPB730, anti-CTLA-4 or GPB730 + anti-CTLA-4. Treatment with anti-CTLA-4 or anti-CTLA-4 + GPB730 significantly inhibited tumor growth and enhanced survival compared to vehicle. Combining anti-CTLA-4 treatment with GPB730 resulted in a significantly prolonged survival compared to anti-CTLA-4 alone. GPB730 significantly increased infiltration of CD45 + cells in tumors of anti-CTLA-4-treated mice compared to anti-CTLA-4 alone. The levels of tumor-infiltrating Tregs were significantly decreased and the CD8:Treg ratio significantly increased by GPB730 treatment in combination with anti-CTLA-4 compared to anti-CTLA-4 alone. Immunohistochemical analysis showed a significant increase in CD45-positive cells in anti-CTLA-4 and anti-CTLA-4 + GPB730-treated tumors compared to vehicle or GPB730 monotherapy. Plasma levels of IL10 were significantly increased by anti-CTLA-4 compared to vehicle but no increase was observed when combining anti-CTLA-4 with GPB730.

In conclusion, STAT3 inhibition by GPB730 enhances the antitumoral activity of anti-CTLA-4 and decreases the intratumoral Treg frequency in a prostate cancer mouse model. These results support the combination of STAT3 inhibition with anti-CTLA-4 therapy to increase clinical responses in patients with prostate cancer.

Inhibition of prostate cancer growth by immunization with a GM-CSF-modified mouse prostate cancer RM-1 cell vaccine in a novel murine model

Advanced prostate cancer is difficult to treat owing to a lack of effective approaches for disrupting immune tolerance. C57BL/6 male and female mice implanted with viable RM-1 cells represent a novel murine model of advanced prostate cancer for studying antitumor effects following immunization with a granulocyte-macrophage colony-stimulating factor (GM-CSF)-modified RM-1 cell vaccine, which has been described previously. In vitro cytotoxic activity and cytokine secretion experiments were conducted to investigate the antitumor response. The cytotoxicity profile of splenocytes from female mice immunized against RM-1 cells primarily involved cytotoxic T lymphocyte (CTL) lysis and, to a lesser extent, natural killer (NK) cell lysis. NK cell lysis was also observed in males, which exhibited no evidence of CTL lysis. The secretion of interferon-γ in the GM-CSF-modified cell vaccine group was significantly increased compared with the other groups. The level of interleukin-4 was low. To investigate the antitumor immune response further, cluster of differentiation 4 (CD4) T cells and CD8 T cells were analyzed in the spleens and tumors of female mice receiving the GM-CSF-modified RM-1 cell vaccine. Unlike female mice, males exhibited the highest proportion of NK cells in the spleen. NK cells were not detected in the tumor tissue in any of the groups. The difference between the sexes may explain the specificity of the immune response, as females are intolerant to prostate antigens whereas males are. This model is clinically relevant as it translates to human immunology and offers an effective and convenient method for studying immunotherapy for prostate cancer.

Enhancing the potency of a whole-cell breast cancer vaccine in mice with an antibody-IL-2 immunocytokine that targets exposed phosphatidylserine

Phosphatidylserine (PS), an anionic phospholipid normally restricted to the inner leaflet of the plasma membrane, is immunosuppressive when externalized on the outside of cell membranes. Exposed PS inhibits the maturation and function of dendritic cells (DCs), and induces the production of multiple immunosuppressive mediators. In the present study, we determined whether blocking these effects of PS while simultaneously introducing interleukin-2 (IL-2) could improve the immunogenicity of a whole-cell cancer vaccine. An immunocytokine (2aG4-IL2) was made by genetically linking IL-2 with a PS targeting antibody, 2aG4, that can block the immunosuppressive effects of PS. The 2aG4-IL2/4T1 vaccine was generated by coating the PS exposed on irradiated 4T1 cells with 2aG4-IL2. Tumor growth, spontaneous metastasis, and survival of vaccinated mice challenged with live 4T1 tumor cells were assessed. Eighty percent of mice inoculated with 2aG4-IL2/4T1 vaccine survived free of tumor, as compared with 20% in the 2aG4/4T1 group, 20% in the C44-IL2/4T1 group, and none in the C44/4T1 control group (P=0.001 for 2aG4-IL2/4T1 versus all others groups). The incidence, number of spontaneous lung metastases was significantly lower in the 2aG4-IL2/4T1 vaccinated group than in the other groups. Splenocytes from 2aG4-IL2/4T1 vaccinated mice had significantly higher 4T1 specific cytotoxicity and ability to secrete interferon-gamma (IFNγ) than did splenocytes from mice in the other groups. These results demonstrate that a potent whole-cell vaccine can be created by coating irradiated tumor cells with 2aG4-IL2. Such vaccine could potentially be an effective treatment modality for patients with residual disease or at "high-risk" for recurrence.

Molecular chemotherapy and chemotherapy: a new front against late-stage hormone-refractory prostate cancer

PURPOSE

Stemming from its inherent heterogeneity, single-agent treatments are essentially ineffective against castration-resistant prostate cancer (CRPC). Thus, clinically relevant regimens that harness different modalities to maximize treatment efficacy without increasing cumulative toxicities are urgently needed. Based on this rationale, we investigated whether a novel combination of purine nucleoside phosphorylase-mediated, gene-directed enzyme-prodrug therapy (PNP-GDEPT) with docetaxel against CRPC has superior efficacy in comparison with individual treatments.

METHODS

The in vitro cell growth inhibition in differentially treated murine and human CRPC cell lines was established using a cell-viability assay. The extent of synergy, additivity, or antagonism between treatments was evaluated using CalcuSyn statistical analyses. The local and systemic effects of docetaxel and/or PNP-GDEPT were tested in both immunodeficient and immunocompetent mice against human and murine CRPC tumors, respectively. Subsequently, immunohistochemical analyses and an evaluation of serum cytokine and serum toxicity profiles were conducted to characterize the differential host responses to treatment.

RESULTS

The combined use of PNP-GDEPT and docetaxel led to strong synergistic cell killing in vitro. Compared with the individual modalities, a combination of the 2 led to a marked reduction in "local and distant" tumor growth in vivo, and importantly, with lowered doses and without additional toxicities. Immunomodulation was indicated by enhanced immune cell infiltration and altered serum cytokine levels. Furthermore, a lowering of T-helper type 2 cytokines, MCP-1, interleukin (IL)-4, IL-6, and IL-10 marked lower tumor burden and enhanced treatment efficacy.

CONCLUSION

PNP-GDEPT and docetaxel are a potent combination against CRPC in immunocompetent and immunodeficient settings; these outcomes have implications of translational potential for improved treatment and management of CRPC patients.

Immunotherapy of MHC class I-deficient tumors

MHC class I downregulation is a general mechanism by which tumor cells can escape from T-cell-mediated immunity. This downregulation also represents a serious obstacle to the development of effective antitumor immunotherapy or vaccination. Therefore, successful immunotherapeutic and vaccination protocols should be optimized against tumors with distinct cell surface expression of the MHC class I molecules. Mechanisms leading to protective immunity may vary in different models with respect to the particular tumors (e.g., in their levels of residual expression of the MHC class I molecules on tumor cells or inducibility of MHC class I expression). Notably, both CD8+ cell-mediated immunity and MHC class I-unrestricted mechanisms can take place against MHC class I-deficient tumors. Since MHC class I downregulation is frequently reversible by cytokines and also by the activation of epigenetically silenced genes, an attractive strategy is to elicit specific cell-mediated immunity combined with restoration of MHC class I expression on tumor cells.

A novel therapeutic vaccine of GM-CSF/TNFalpha surface-modified RM-1 cells against the orthotopic prostatic cancer

A novel therapeutic vaccine against prostate cancer was developed by simultaneous immobilization of streptavidin-tagged bioactive GM-CSF and TNFalpha on the biotinylated surface of 30% ethanol-fixed RM-1 prostatic cancer cells. This study showed that the GM-CSF/TNFalpha-doubly surface-modified vaccine significantly extended the survival in the orthotopic model of RM-1 prostate cancer, and was superior to single GM-CSF- or TNFalpha-surface-modified vaccine. Moreover, the splenocytes from the GM-CSF/TNFalpha-vaccine-treated mice showed the most potent cytotoxicity on RM-1 cells and the highest production of RM-1-specific IFNgamma. In addition, more CD4+ and CD8+ T cells infiltrated into the tumor sites in the GM-CSF/TNFalpha-vaccine-treated mice than in the GM-CSF- or TNFalpha-vaccine-treated mice. Therefore, our study demonstrated that the efficacy of RM-1 prostate cancer cell vaccine could be improved by conjugating both GM-CSF and TNFalpha simultaneously on the surface of cancer cells, and that this modification thus has a potential translational significance.

Intraosseous injection of RM1 murine prostate cancer cells promotes rapid osteolysis and periosteal bone deposition

The molecular mechanisms associated with prostate cancer (PCa) progression within bone remain a topic of intense investigation. With the availability of transgenic mouse strains, a model of PCa for use in immune competent/transgenic mice would be highly beneficial. This study was designed to explore the utility of RM1 mouse PCa cells in investigations of tumor:bone interactions. The efficacies of several implantation techniques were examined for reliably producing intra-bone RM1 tumor growth and bone lesion formation in immune competent mice. Longitudinal monitoring of bone remodeling and lesion phenotypes was conducted by microcomputed tomography (muCT) and histological analyses. Our results indicate that direct intrabone injections of RM1 cells are necessary for tumor growth within bone and direct implantation promotes the rapid development of osteolytic bone lesions with periosteal bone deposition post-cortical breach. In vitro, RM1 cells promote the proliferation of osteoblast (MC3T3-E1) and osteoclast (Raw264.7) progenitors in a dose dependent manner. Conditioned culture media from RM1 cells appears to promote earlier expression of genes/proteins associated with osteoblastic differentiation. While clearly stimulating osteoclast function in vivo, RM1 cells had little effect on differentiation and tartate resistant acid phosphatase (TRAP) expression by Raw264.7 cells. These data, coupled with in vivo muCT images, indicate the ability of RM1 cells to induce mixed, yet predominentally osteolytic, responses in bone and illustrate the potential of RM1 cells as a model of investigating prostate tumor:stroma interactions in immune competent/transgenic mice on a C57BL/6 background.

Anti-tumor immunostimulatory effect of heat-killed tumor cells

As a part of our ongoing search for a safe and efficient anti-tumor vaccine, we attempted to determine whether the molecular nature of certain tumor antigens would influence immune responses against tumor cells. As compared with freeze-thawed or formaldehyde-fixed tumor antigens, heat-denatured tumor antigens elicited profound anti-tumor immune responses and greatly inhibited the growth of live tumor cells. The heat-denatured tumor antigens induced a substantial increase in the anti-tumor CTL response in the absence of any adjuvant material. This response appears to be initiated by strong activation of the antigen-presenting cells, which may recognize heat-denatured protein antigens. Upon recognition of the heat-denatured tumor antigens, macrophages and dendritic cells were found to acutely upregulate the expression of co-stimulatory molecules such as B7.2, as well as the secretion of inflammatory cytokines such as IL-12 and TNF-alpha. The results of this study indicate that heat-denatured tumor extracts might elicit protective anti-tumor adaptive immune responses and also raise the possibility that a safe and efficient adjuvant-free tumor vaccine might be developed in conjunction with a dendritic cell-based tumor vaccine.