Pretreatment with cisplatin enhances E7-specific CD8+ T-Cell-mediated antitumor immunity induced by DNA vaccination

Identification of novel immunogenic human leukocyte antigen-A 2402-binding epitopes of human papillomavirus type 16 E7 for immunotherapy against human cervical cancer

BACKGROUND

A study was undertaken to identify new immunogenic human leukocyte antigen (HLA)-A 2402-restricted epitopes from human papillomavirus (HPV) type 16 E7 protein for immunotherapy against cervical cancer.

METHODS

Synthetic overlapping peptides were screened by measuring the frequency of CD8(+) cytotoxic T lymphocytes (CTLs) producing intracellular interferon-γ (IFN-γ) using flow cytometry and were validated in SiHa cells with a Cr release cytotoxicity assay. In vivo antitumor effects of peptide-sensitized peripheral blood mononuclear cells (PBMCs) and isolated CD8(+) CTLs were evaluated using BALB/c nude mice with SiHa cell xenotransplants.

RESULTS

Among 14 overlapping 15-amino acid peptides, E7(61-75) (CDSTLRLCVQSTHVD) and E7(67-81) (LCVQSTHVDIRTLED) induced significantly higher IFN-γ production (P < .05) and showed higher in vitro cytotoxicity against SiHa cells than did cells sensitized with the negative control. To determine the exact HLA-A 2402-restricted epitopes, a total of 25 overlapping 9- or 10-amino acid peptides spanning E7(61-75) and E7(67-81) were synthesized. E7(61-69) (CDSTLRLCV) and E7(67-76) (LCVQSTHVDI) induced significantly greater IFN-γ production as well as increased in vitro cytotoxicity against SiHa cells compared with those of other peptides and the negative control (P < .01), and the antitumor effects of these peptide-sensitized PBMCs were induced by CD8(+) CTLs. E7(61-69) -sensitized and E7(67-76) -sensitized PBMCs and isolated CD8(+) CTLs showed a much greater suppression of tumor growth in vivo compared with that of control groups treated with PBS (P < .01). The authors also confirmed the synergistic antitumor effect of cisplatin followed by E7(67-76) -sensitized PBMCs in vivo.

CONCLUSIONS

E7(61-69) and E7(67-76) were identified as novel HPV type 16 E7 epitopes for HLA-A 2402, which could be used for immunotherapy against cervical cancer.

Exploitation of differential homeostatic proliferation of T-cell subsets following chemotherapy to enhance the efficacy of vaccine-mediated antitumor responses

The 5-year survival rate for stage IB-III non-small-cell lung cancer (NSCLC) remains 15%. Surgical resection followed by adjuvant chemotherapy with cisplatin and vinorelbine is one standard-of-care. We sought to determine in a preclinical model whether (a) the combination of cisplatin and vinorelbine could positively modulate components of the immune system independent of antitumor activity, and (b) there were synergistic effects of this drug combination and vaccine immunotherapy. We examined the effect of cisplatin/vinorelbine on gene expression, cell-surface phenotype, and CTL-mediated cytolysis of murine lung carcinoma cells in vitro; we also assessed the effects of cisplatin/vinorelbine on immune subsets and function of Tregs in vivo. Finally, we evaluated the potential synergy between chemotherapy and a recombinant yeast-CEA vaccine in a murine model transgenic for CEA with mice bearing lung tumors. These studies demonstrate that exposure of lung tumor cells to the platinum doublet cisplatin/vinorelbine modulates tumor cell phenotype and increases sensitivity to CTL-mediated cytolysis. These studies also demonstrate that cisplatin/vinorelbine (a) induces sub-myeloablative leucopenia that differentially modulates reconstitution of Treg versus effector T-cell subsets and (b) can be employed synergistically with vaccine, exploiting homeostatic peripheral expansion of T cells. Antitumor studies show for the first time that cisplatin/vinorelbine combined with vaccine increases the survival of mice with established NSCLC. These findings provide the rationale for the potential clinical benefit of the combined use of vaccine with cisplatin/vinorelbine chemotherapy regimens.

Chemoimmunotherapy

Cancer chemotherapy drugs are historically regarded as detrimental to immunity because of their myelosuppressive effects. However, accumulating data suggest that the antitumor activity of conventional cancer chemotherapy results in part from its ability to harness the innate and adaptive immune systems by inducing immunologically active tumor cell death. Additional data broaden the immunologic effect of cancer chemotherapy drugs, demonstrating that some drugs have the ability to disrupt pathways of immune suppression and immune tolerance in a manner that depends on the drug dose, and the timing of its administration in relation to immunotherapy. Understanding the cellular and molecular basis of the interactions between chemotherapy drugs and the immune system will facilitate the strategic development of chemoimmunotherapy treatment regimens that both maximize tumor regression and the antitumor immune response for the long-term clinical benefit of cancer patients.

Therapeutic HPV DNA vaccines

It is now well established that most cervical cancers are causally associated with HPV infection. This realization has led to efforts to control HPV-associated malignancy through prevention or treatment of HPV infection. Currently, commercially available HPV vaccines are not designed to control established HPV infection and associated premalignant and malignant lesions. To treat and eradicate pre-existing HPV infections and associated lesions which remain prevalent in the U.S. and worldwide, effective therapeutic HPV vaccines are needed. DNA vaccination has emerged as a particularly promising form of therapeutic HPV vaccines due to its safety, stability and ability to induce antigen-specific immunity. This review focuses on improving the potency of therapeutic HPV vaccines through modification of dendritic cells (DCs) by [1] increasing the number of antigen-expressing/antigen-loaded DCs, [2] improving HPV antigen expression, processing and presentation in DCs, and [3] enhancing DC and T cell interaction. Continued improvement in therapeutic HPV DNA vaccines may ultimately lead to an effective DNA vaccine for the treatment of HPV-associated malignancies.

Promoting effect of Antrodia camphorata as an immunomodulating adjuvant on the antitumor efficacy of HER-2/neu DNA vaccine

It is well known that DNA vaccines induce protective humoral and cell-mediated immune responses in several animal models. Antrodia camphorata (AC) is a unique basidiomycete fungus of the Polyporaceae family that only grows on the aromatic tree Cinnamomum kanehirai Hayata (Lauraceae) endemic to Taiwan. Importantly, AC has been shown to be highly beneficial in the treatment and prevention of cancer. The goal of this study was to investigate whether AC is able to augment the antitumor immune properties of a HER-2/neu DNA vaccine in a mouse model in which p185neu is overexpressed in MBT-2 tumor cells. Compared with the mice that received the HER-2/neu DNA vaccine alone, co-treatment with AC suppressed tumor growth and extended the survival rate. This increase in the antitumor efficacy was attributed to the enhancement of the Th1-like cellular immune response by the HER-2/neu DNA vaccine-AC combination. Evidence for this came from the marked increase in the IFN-gamma mRNA expression in CD4+ T cells in the draining inguinal lymph nodes, an increase in the number of functional HER-2/neu-specific CTLs, and the increased tumor infiltration of both CD4+ and CD8+ T cells, depletion of which abolishes the antitumor effect of the HER-2/neu DNA vaccine-AC therapy. Our results further indicate that the treatment of mice with AC enhanced DC activation and production of Th1-activating cytokines (e.g. IL-12, and IFN-alpha) in the draining lymph nodes, which were sufficient to directly stimulate T cell proliferation and higher IFN-gamma production in response to ErbB2. Overall, these results clearly demonstrate that AC represents a promising immunomodulatory adjuvant that could enhance the therapeutic potency of HER-2/neu DNA vaccines in cancer therapy.

Delivery of chemotherapeutic agents using drug-loaded irradiated tumor cells to treat murine ovarian tumors

Background

Ovarian cancer is the leading cause of death among women with gynecologic malignancies in the United States. Advanced ovarian cancers are difficult to cure with the current available chemotherapy, which has many associated systemic side effects. Doxorubicin is one such chemotherapeutic agent that can cause cardiotoxicity. Novel methods of delivering chemotherapy without significant side effects are therefore of critical need.

Methods

In the current study, we generated an irradiated tumor cell-based drug delivery system which uses irradiated tumor cells loaded with the chemotherapeutic drug, doxorubicin.

Results

We showed that incubation of murine ovarian cancer cells (MOSEC) with doxorubicin led to the intracellular uptake of the drug (MOSEC-dox cells) and the eventual death of the tumor cell. We then showed that doxorubicin loaded MOSEC-dox cells were able to deliver doxorubicin to MOSEC cells in vivo. Further characterization of the doxorubicin transfer revealed the involvement of cell contact. The irradiated form of the MOSEC-dox cells were capable of treating luciferase-expressing MOSEC tumor cells (MOSEC/luc) in C57BL/6 mice as well as in athymic nude mice resulting in improved survival compared to the non drug-loaded irradiated MOSEC cells. Furthermore, we showed that irradiated MOSEC-dox cells was more effective compared to an equivalent dose of doxorubicin in treating MOSEC/luc tumor-bearing mice.

Conclusions

Thus, the employment of drug-loaded irradiated tumor cells represents a potentially innovative approach for the delivery of chemotherapeutic drugs for the control of ovarian tumors.

DNA vaccines for cervical cancer

Human papillomavirus (HPV), particularly type 16, has been associated with more than 99% of cervical cancers. There are two HPV oncogenic proteins, E6 and E7, which play a major role in the induction and maintenance of cellular transformation. Thus, immunotherapy targeting these proteins may be employed for the control of HPV-associated cervical lesions. Although the commercially available preventive HPV vaccines are highly efficient in preventing new HPV infection, they do not have therapeutic effects against established HPV infection or HPV-associated lesions. Since T cell-mediated immunity is important for treating established HPV infections and HPV-associated lesions, therapeutic HPV vaccine should aim at generating potent E6 and E7-specific T cell-mediated immune responses. DNA vaccines have now developed into a promising approach for antigen-specific T cell-mediated immunotherapy to combat infection and cancer. Because dendritic cells are the most potent professional antigen-presenting cells, and are highly effective in priming antigen-specific T cells, several DNA vaccines have employed innovative strategies to modify the properties of dendritic cells (DCs) for the enhancement of the DNA vaccine potency. These studies have revealed impressive pre-clinical data that has led to several ongoing HPV DNA vaccine clinical trials.

Therapeutic HPV DNA vaccines

Human papillomavirus (HPV) has been associated with several human cancers, including cervical cancer, vulvar cancer, vaginal and anal cancer, and a subset of head and neck cancers. The identification of HPV as an etiological factor for HPV-associated malignancies creates the opportunity for the control of these cancers through vaccination. Currently, the preventive HPV vaccine using HPV virus-like particles has been proven to be safe and highly effective. However, this preventive vaccine does not have therapeutic effects, and a significant number of people have established HPV infection and HPV-associated lesions. Therefore, it is necessary to develop therapeutic HPV vaccines to facilitate the control of HPV-associated malignancies and their precursor lesions. Among the various forms of therapeutic HPV vaccines, DNA vaccines have emerged as a potentially promising approach for vaccine development due to their safety profile, ease of preparation and stability. However, since DNA does not have the intrinsic ability to amplify or spread in transfected cells like viral vectors, DNA vaccines can have limited immunogenicity. Therefore, it is important to develop innovative strategies to improve DNA vaccine potency. Since dendritic cells (DCs) are key players in the generation of antigen-specific immune responses, it is important to develop innovative strategies to modify the properties of the DNA-transfected DCs. These strategies include increasing the number of antigen-expressing/antigen-loaded DCs, improving antigen processing and presentation in DCs, and enhancing the interaction between DCs and T cells. Many of the studies on DNA vaccines have been performed on preclinical models. Encouraging results from impressive preclinical studies have led to several clinical trials.

Targeting and retention of HPV16 E7 to the endoplasmic reticulum enhances immune tumour protection

The endoplasmic reticulum (ER) is where the major histocompatibility complex (MHC) class I molecules are loaded with epitopes to cause an immune cellular response. Most of the protein antigens are degraded in the cytoplasm to amino acids and few epitopes reach the ER. Antigen targeting of this organelle by Calreticulin (CRT) fusion avoids this degradation and enhances the immune response. We constructed a recombinant adenovirus to express the E7 antigen with an ER-targeting signal peptide (SP) plus an ER retention signal (KDEL sequence). In cell-culture experiments we demonstrated that this new E7 antigen, SP-E7-KDEL, targeted the ER. Infection of mice with this recombinant adenovirus that expresses SP-E7-KDEL showed interferon induction and tumour-protection response, similar to that provided by an adenovirus expressing the E7 antigen fused to CRT. This work demonstrated that just by adding a SP and the KDEL sequence, antigens can be targeted and retained in the ER with a consequent enhancement of immune response and tumour protection. These results will have significant clinical applications.

Combination of apigenin treatment with therapeutic HPV DNA vaccination generates enhanced therapeutic antitumor effects

BACKGROUND

It is important to develop innovative therapies for advanced stage cancers in addition to the conventional therapies including chemotherapy, radiation and surgery. Antigen-specific immunotherapy has emerged as a novel alternate therapy for advanced stage cancers, which may be employed in conjunction with conventional therapies.

METHODS

In the current study, we tested the effect of treatment with the chemotherapeutic agent, apigenin in combination with DNA vaccines encoding the HPV-16 E7 antigen linked to heat shock protein 70 (HSP70) in the control of the E7-expressing tumor, TC-1.

RESULTS

We observed that treatment with apigenin rendered the TC-1 tumor cells more susceptible to lysis by E7-specific cytotoxic CD8+ T cells. Furthermore, treatment of TC-1 tumor cells with apigenin was found to enhance apoptotic tumor cell death in vitro in a dose-dependant manner. We showed that TC-1 tumor-bearing mice treated with apigenin combined with E7-HSP70 DNA generate highest frequency of primary and memory E7-specific CD8+ T cells, leading to potent therapeutic anti-tumor effects against E7-expressing tumors.

CONCLUSION

Thus, apigenin represents a promising chemotherapeutic agent, which may be used in combination with immunotherapy for the treatment of advanced stage cancers. The clinical implications of the current strategy are discussed.

Adoptive transfer of human papillomavirus E7-specific CTL enhances tumor chemoresponse through the perforin/granzyme-mediated pathway

Adoptive cytotoxic T lymphocyte (CTL) therapy has an important implication in treating cancer patients. Here, we investigate whether adoptive transfer of human papillomavirus (HPV) E7-specific CTL can enhance tumor chemoresponse using an established cervical cancer animal model. Cisplatin-based chemotherapy plus CTL therapy showed an improved therapeutic effectiveness, along with antitumor protective responses to a parental tumor cell rechallenge. Cisplatin treatment dose-dependently increased the expression of Fas, intercellular adhesion molecule (ICAM)-1, and major histocompatibility complex (MHC) class I antigens (Ags) on tumor cells in vitro. However, CTL-expressing FasL failed to improve antitumor activity in vitro and in animals, resulting from nonfunctional Fas expressed on tumor cells. In contrast, ethylene glycol tetraacetic acid (EGTA) treatment blocked increased sensitivity of cisplatin-treated tumor cells to CTL-mediated killing in vitro, suggesting an important role of the perforin/granzyme-mediated pathway for improved therapeutic effectiveness. This notion was further confirmed by perforin knockout animal studies. Thus, this study shows that (i) modulation of Ag (Fas, ICAM-1) expression by tumor cells has little effect on their increased sensitivity to CTL-mediated killing, (ii) improved therapeutic effectiveness is mediated mainly through the perforin/granzyme-mediated tumor killing pathway, and (iii) a combination of chemotherapy and adoptive E7-specific CTL transfer augments antitumor therapeutic activity in vivo. This finding may have important implications for treating HPV-associated cervical cancer.

Treatment with demethylating agent, 5-aza-2'-deoxycytidine enhances therapeutic HPV DNA vaccine potency

DNA vaccines have emerged as a potential alternative to current strategies to control cancer for their safety, stability and ease of preparation. We have previously demonstrated that a DNA vaccine encoding calreticulin (CRT) linked to human papillomavirus type 16 (HPV-16) E7 antigen (CRT/E7) can generate significant E7-specific immune responses and antitumor effects in vaccinated mice, thus enhancing DNA vaccine potency. Another strategy to improve DNA vaccine potency is by enhancing the level of expression of the antigen encoded in the vaccine. DNA methylation has been shown to lead to silencing of the genes that would affect the expression of the encoded antigen of the DNA vaccines. In the current study, we reasoned that CRT/E7 DNA vaccination combined with demethylating agent, 5-aza-2'-deoxycytidine (DAC) would lead to upregulation of CRT/E7 expression, resulting in improved DNA vaccine potency. We found that pre-treatment with DAC led to increased CRT/E7 DNA expression, leading to enhanced E7-specific CD8+ T cell immune responses as well as the antitumor effects generated by the CRT/E7 DNA vaccine. Thus, our data suggest that combination of CRT/E7 DNA vaccination with DAC treatment may represent a potentially promising approach to control HPV-associated malignancies. The clinical implications of this study are discussed.

Enhancing therapeutic HPV DNA vaccine potency through depletion of CD4+CD25+ T regulatory cells

Therapeutic human papillomavirus (HPV) vaccines targeting E6 and/or E7 antigens represent an opportunity to control HPV-associated lesions. We have previously generated several therapeutic DNA vaccines targeting HPV-16 E7 antigen and generated significant antitumor effects. Since regulatory T cells (Tregs) play an important role in suppressing immune responses against tumors by immunotherapy, such as DNA vaccines, we tested if the therapeutic effects of a DNA vaccine encoding E7 linked to heat shock protein 70 (Hsp70) can be improved by a strategy to deplete Tregs using a anti-CD25 monoclonal antibody (PC61) in vaccinated mice. We found that administration of PC61 prior to vaccination with E7/Hsp70 DNA was capable of generating higher levels of E7-specific CD8(+) T cells compared to the control antibody, leading to significantly improved therapeutic and long-term protective antitumor effects against an E7-expressing tumor, TC-1. Thus, a strategy to deplete CD4(+)CD25(+) Tregs in conjunction with therapeutic tumor antigen-specific DNA vaccine may represent a potentially promising approach to control tumor. The clinical implications of our study are discussed.

Low-dose radiation enhances therapeutic HPV DNA vaccination in tumor-bearing hosts

Current therapeutic approaches to treatment of patients with bulky cervical cancer are based on conventional in situ ablative modalities including cisplatin-based chemotherapy and radiation therapy. The 5-year survival of patients with nonresectable disease is dismal. Because over 99% of squamous cervical cancer is caused by persistent infection with an oncogenic strain of human papillomavirus (HPV), particularly type 16 and viral oncoproteins E6 and E7 are functionally required for disease initiation and persistence, HPV-targeted immune strategies present a compelling opportunity in which to demonstrate proof of principle. Sublethal doses of radiation and chemotherapeutic agents have been shown to have synergistic effect in combination with either vaccination against cancer-specific antigens, or with passive transfer of tumor-specific cytotoxic T lymphocytes (CTLs). Here, we explored the combination of low-dose radiation therapy with DNA vaccination with calreticulin (CRT) linked to the mutated form of HPV-16 E7 antigen (E7(detox)), CRT/E7(detox) in the treatment of E7-expressing TC-1 tumors. We observed that TC-1 tumor-bearing mice treated with radiotherapy combined with CRT/E7(detox) DNA vaccination generated significant therapeutic antitumor effects and the highest frequency of E7-specific CD8(+) T cells in the tumors and spleens of treated mice. Furthermore, treatment with radiotherapy was shown to render the TC-1 tumor cells more susceptible to lysis by E7-specific CTLs. In addition, we observed that treatment with radiotherapy during the second DNA vaccination generated the highest frequency of E7-specific CD8(+) T cells in the tumors and spleens of TC-1 tumor-bearing mice. Finally, TC-1 tumor-bearing mice treated with the chemotherapy in combination with radiation and CRT/E7(detox) DNA vaccination generate significantly enhanced therapeutic antitumor effects. The clinical implications of the study are discussed.

Combination of treatment with death receptor 5-specific antibody with therapeutic HPV DNA vaccination generates enhanced therapeutic anti-tumor effects

There is currently a vital need for the development of novel therapeutic strategies for the control of advanced stage cancers. Antigen-specific immunotherapy and the employment of antibodies against the death receptor 5 (DR5) have emerged as two potentially promising strategies for cancer treatment. In the current study, we hypothesize that the combination of treatment with the anti-DR5 monoclonal antibody, MD5-1 with a DNA vaccine encoding calreticulin (CRT) linked to human papillomavirus type 16 (HPV-16) E7 antigen (CRT/E7(detox)) administered via gene gun would lead to further enhancement of E7-specific immune responses as well as anti-tumor effects. Our results indicated that mice bearing the E7-expressing tumor, TC-1 treated with MD5-1 monoclonal antibody followed by CRT/E7(detox) DNA vaccination generated the most potent therapeutic anti-tumor effects as well as highest levels of E7-specific CD8+ T cells among all the groups tested. In addition, treatment with MD5-1 monoclonal antibody was capable of rendering the TC-1 tumor cells more susceptible to lysis by E7-specific cytotoxic T lymphocytes. Our findings serve as an important foundation for future clinical translation.