Vaccines to treat cancer--an old approach whose time has arrived

From the Hellstrom paradox toward cancer cure

Several decades ago we published some of the first papers showing that both murine and human cancers are recognized in vitro as immunologically foreign and that this is the case also in the presence of a growing tumor. The latter situation, sometimes referred to as the Hellstrom paradox, implies that the tumor is protected in vivo by a highly immunosuppressive environment. After many disappointments, the discovery that tumor-related immunosuppression can be counteracted by administrating monoclonal antibodies (mAbs) to checkpoint inhibitors such as CTLA-4, PD-1, and PD-L1 is now revolutionizing cancer therapy. Over the past several years we have applied mouse models in attempts to further improve the ability of such mAbs to cause long-term complete tumor rejection. This review is focused on that work and emphasizes that successful immunotherapy is associated with a shift from a tumor-promoting Th2 inflammation to a tumor-inhibiting Th1 response.

Antitumorpharmacological mechanism of the oral liquid of Poriacocos polysaccharide

ETHNOPHARMACOLOGICAL RELEVANCE

The liquid oral formulation of Poria cocos polysaccharides is composed of polysaccharides of Lentinusedodes, Ganodermalucidum and Poria cocos(1:1:2), which are all fungi used in traditional Chinese medicine. Polysaccharides extracted from these fungi have been reported to exhibit an antitumor effect by modulating the immune system.

AIM OF THE STUDY

The present study aimed to clarify the antitumor mechanism of an orally administered liquid containing Poriacocos and to further provide clinical guidance.

MATERIALS AND METHODS

In this study, the effects of an orally administered liquid containing Poriacocos polysaccharides on the solid tumors formed from sarcoma 180 cells in mice were evaluated. The protein expression of Bcl-2, caspase-3, and caspase-9in the thymus, spleen and liver tissues in the mice was determined by Western blot analysis. In addition, hematoxylin-eosin（H&E）staining and immunohistochemistry were performed on thymus, spleen and liver tissue and the positive staining rate was calculated for the three protein expression.

RESULTS

The liquid oral formulation of Poriacocos polysaccharides reduced Bcl-2 protein levels and increased caspase-3 and -9 protein levels in sarcoma 180 cells.

CONCLUSION

The mechanism underlying the antitumor effects of the oral liquid formulation of Poriacocos polysaccharides involved inhibition of Bcl-2 expression and activation of caspase-9 expression in sarcoma 180 cells. Furthermore, the downstream caspase-3 promoter cascade was activated and cell apoptosis was activated in sarcoma 180 cells.

Th2 type inflammation promotes the gradual progression of HPV-infected cervical cells to cervical carcinoma

OBJECTIVES

To investigate the role of immunological parameters in tumorigenesis of cervical cancer in women infected with high risk human papillomavirus (hr-HPV), and determine whether key findings with human material can be recapitulated in the mouse TC1 carcinoma model which expresses hr-HPV epitopes.

METHODS

Epithelial and lymphoid cells in cervical tissues were analyzed by immunohistochemistry and serum IL10 levels were determined by ELISA. Tumor draining lymph nodes were analyzed in the mouse TC1 model by flow cytometry.

RESULTS

The mucosa was infiltrated by CD20+ and CD138+ cells already at cervical intraepithelial neoplasia 1 (CIN1) and infiltration increased in cervical intraepithelial neoplasia 3 (CIN3)/carcinoma in situ (CIS) and invasive cervical cancer (ICC), where it strongly correlated with infiltration by CD32B+ and FoxP3+ lymphocytes. GATA3+ and T-bet+ lymphoid cells were increased in ICC compared to normal, and expression in epithelial cells of the Th2 inflammation-promoting cytokine TSLP and of IDO1 was higher in CIN3/CIS and ICC. As a corollary, serum levels of IL10 were higher in women with CIN3/CIS or ICC than in normals. Finally we demonstrated in the mouse TC1 carcinoma, which expresses hr-HPV epitopes, an increase of cells expressing B cell or plasma cell markers or Fc receptors in tumor-draining than distal lymph nodes or spleen.

CONCLUSIONS

hr-HPV initiates a local Th2 inflammation at an early stage, involving antibody forming cells, and fosters an immunosuppressive microenvironment that aids tumor progression.

The hen model of human ovarian cancer develops anti-mesothelin autoantibodies in response to mesothelin expressing tumors

Objective

Study of the hen immune system led to seminal contributions to basic immunological principles. Recent studies of spontaneous ovarian cancer in the laying hen show strikingly similar tumor types and antigen expression compared to human ovarian cancer, suggesting hens would be valuable for studies of tumor immunology and pre-clinical vaccine development. Circulating mesothelin is a relatively specific marker for human ovarian cancer and autoantibodies to mesothelin were reported. We hypothesized that hen tumors express mesothelin and that circulating anti-mesothelin antibodies occur in response to tumors.

Methods

Mesothelin mRNA expression was analyzed by RT-PCR in hen ovarian tumors and normal ovaries. Mesothelin protein expression was evaluated by immunohistochemistry (IHC) and two-dimensional SDS-PAGE Western blots. Anti-mesothelin antibodies were assessed by immunoassay of sera from hens with normal ovaries and with ovarian tumors.

Results

Significant mesothelin mRNA expression was observed in 57% (12/21) of hen ovarian tumors but not in normal ovaries and was found predominantly in serous tumors as in humans. Mesothelin protein was detected in tumors with mesothelin mRNA by IHC and 2D Western blots, but not in normal ovaries or tumors without mesothelin mRNA. Circulating anti-mesothelin antibodies occurred in 44% (n = 4/9) of hens with ovarian tumors which express mesothelin mRNA and were not found in hens with tumors that did not express mesothelin (n = 0/5) or normal ovaries (n = 0/5).

Conclusion

The results support the utility of the hen as a novel model for preclinical studies of mesothelin as a biomarker and a target for immunotherapy.

Immunomodulatory effects of cyclophosphamide and implementations for vaccine design

Drug repositioning refers to the utilization of a known compound in a novel indication underscoring a new mode of action that predicts innovative therapeutic options. Since 1959, alkylating agents, such as the lead compound cyclophosphamide (CTX), have always been conceived, at high dosages, as potent cytotoxic and lymphoablative drugs, indispensable for dose intensity and immunosuppressive regimen in the oncological and internal medicine armamentarium. However, more recent work highlighted the immunostimulatory and/or antiangiogenic effects of low dosing CTX (also called "metronomic CTX") opening up novel indications in the field of cancer immunotherapy. CTX markedly influences dendritic cell homeostasis and promotes IFN type I secretion, contributing to the induction of antitumor cytotoxic T lymphocytes and/or the proliferation of adoptively transferred T cells, to the polarization of CD4(+) T cells into TH1 and/or TH17 lymphocytes eventually affecting the Treg/Teffector ratio in favor of tumor regression. Moreover, CTX has intrinsic "pro-immunogenic" activities on tumor cells, inducing the hallmarks of immunogenic cell death on a variety of tumor types. Fifty years after its Food and Drug Administration approval, CTX remains a safe and affordable compound endowed with multifaceted properties and plethora of clinical indications. Here we review its immunomodulatory effects and advocate why low dosing CTX could be successfully combined to new-generation cancer vaccines.

Local release of highly loaded antibodies from functionalized nanoporous support for cancer immunotherapy

We report that antibodies can be spontaneously loaded in functionalized mesoporous silica (FMS) with superhigh density (0.4-0.8 mg of antibody/mg of FMS) due to their comprehensive noncovalent interaction. The superhigh loading density and noncovalent interaction between FMS and antibodies allow long-lasting local release of the immunoregulatory molecules from FMS under physiological conditions. Preliminary data indicate that FMS-anti-CTLA4 antibody injected directly into a mouse melanoma induces much greater and extended inhibition of tumor growth than the antibody given systemically. Our findings open up a novel approach for local delivery of therapeutically active proteins to tumors and, potentially, other diseases.

Administration of cyclophosphamide changes the immune profile of tumor-bearing mice

Cyclophosphamide (CTX) is often used to create a "window" for more effective therapeutic tumor vaccination. According to a commonly applied protocol, we injected 2 mg CTX intraperitoneally to mice with small (2 to 3 mm diameter) or large (5 to 7 mm, and in one experiment 8 to 10 mm diameter) subcutaneously growing tumors from the SW1 clone of the K1735 melanoma, euthanized the mice 4 days later and studied the composition of lymphoid cells by flow cytometry in both spleens and tumors. Administration of CTX increased the percentage of CD3, CD4, and CD8 cells with the increase in tumors being significantly greater than in spleens, and it also increased the percentage of B cells in spleens and tumors. Furthermore, CTX dramatically increased the frequency of tumor-infiltrating CD4 and CD8 cells containing interferon gamma, of cells expressing NK1.1, and of cells expressing the dendritic cell markers CD11c, CD80, and CD86, with the greatest increases seen among tumor-infiltrating lymphoid cells (TIL) from mice with small tumors. Although CTX decreased the percentage of TIL that expressed CD4 or CD8 together with CD25 and FoxP3 and were therefore considered to be regulatory T cells, it increased the frequency of TIL that stained for Gr1/CD11b, a marker for myeloid-derived suppressor cells. We conclude that the administration of CTX can favorably impact several cell populations that are involved in tumor rejection. However, since CTX has a limited effect on TIL from tumors larger than a few millimeter in diameter and in view of an increased percentage of myeloid-derived suppressor cells among TIL from mice given CTX there is a need for more effective ways to improve tumor vaccination.

Chemotherapy induced transient B-cell depletion boosts antibody-forming cells expansion driven by an epidermal growth factor-based cancer vaccine

Cancer vaccines efficacy may improve inducing a rapid and persistent immune response, early at diagnosis along with standard therapies. EGF chemically conjugated to the carrier protein P64k from Neisseria meningitidis in montanide ISA 51 adjuvant is under evaluation, aiming to stimulate a B-cell response. High-dose cyclophosphamide and doxorubicin after priming enhanced the long-term frequency of EGF-specific antibody-forming cells (AFC) of IgM and IgG isotypes, but not the P64k response. Resulting combination, limitedly operational in Btk deficient xid mice, suggests that preferential B-cell lymphocyte space promoted by cyclophosphamide facilitates remaining EGF-specific AFC undergo homeostatic proliferation driven by boosting, amplifying the response.