Bedside to bench and back again: how animal models are guiding the development of new immunotherapies for cancer

Design and Evaluation of Synthetic Delivery Formulations for Peptide-Based Cancer Vaccines

With the recent advances in neoantigen identification, peptide-based cancer vaccines offer substantial potential in the field of immunotherapy. However, rapid clearance, low immunogenicity, and insufficient antigen-presenting cell (APC) uptake limit the efficacy of peptide-based cancer vaccines. This review explores the barriers hindering vaccine efficiency, highlights recent advancements in synthetic delivery systems, and features strategies for the key delivery steps of lymph node (LN) drainage, APC delivery, cross-presentation strategies, and adjuvant incorporation. This paper also discusses the design of preclinical studies evaluating vaccine efficiency, including vaccine administration routes and murine tumor models.

Genome-wide analysis of genetic predisposition to common polygenic cancers

Lung, breast, prostate, and colorectal cancers are among the most common and fatal malignancies worldwide. They are mainly caused by multifactorial mechanisms and are genetically heterogeneous. We investigated the genetic architecture of these cancers through genome-wide association, pathway-based, and summary-based transcriptome-/methylome-wide association analyses using three independent cohorts. Our genome-wide association analyses identified the associations of 33 single-nucleotide polymorphisms (SNPs) at P < 5E - 06, of which 32 SNPs were not previously reported and did not have proxy variants within their ± 1 Mb flanking regions. Moreover, other polymorphisms mapped to their closest genes were not previously associated with the same cancers at P < 5E - 06. Our pathway enrichment analyses revealed associations of 32 pathways; mainly related to the immune system, DNA replication/transcription, and chromosomal organization; with the studied cancers. Also, 60 probes were associated with these cancers in our transcriptome-wide and methylome-wide analyses. The ± 1 Mb flanking regions of most probes had not attained P < 5E - 06 in genome-wide association studies. The genes corresponding to the significant probes can be considered as potential targets for further functional studies. Two genes (i.e., CDC14A and PMEL) demonstrated stronger evidence of associations with lung cancer as they had significant probes in both transcriptome-wide and methylome-wide association analyses. The novel cancer-associated SNPs and genes identified here would advance our understanding of the genetic heterogeneity of the common cancers.

A systematic analysis of experimental immunotherapies on tumors differing in size and duration of growth

We conducted a systematic analysis to determine the reason for the apparent disparity of success of immunotherapy between clinical and experimental cancers. To do this, we performed a search of PubMed using the keywords “immunotherapy” AND “cancer” for the years of 1980 and 2010. The midspread of experimental tumors used in all the relevant literature published in 2010 were between 0.5–121 mm³ in volume or had grown for four to eight days. Few studies reported large tumors that could be considered representative of clinical tumors, in terms of size and duration of growth. The predominant effect of cancer immunotherapies was slowed or delayed outgrowth. Regression of tumors larger than 200 mm³ was observed only after passive antibody or adoptive T cell therapy. The effectiveness of other types of immunotherapy was generally scattered. By comparison, very few publications retrieved by the 1980 search could meet our selection criteria; all of these used tumors smaller than 100 mm³, and none reported regression. In the entire year of 2010, only 13 used tumors larger than 400 mm³, and nine of these reported tumor regression. Together, these results indicate that most recent studies, using many diverse approaches, still treat small tumors only to report slowed or delayed growth. Nevertheless, a few recent studies indicate effective therapy against large tumors when using passive antibody or adoptive T cell therapy. For the future, we aspire to witness the increased use of experimental studies treating tumors that model clinical cancers in terms of size and duration of growth.

Adoptive T-Cell Transfer to Treat Lymphangioleiomyomatosis

Patients with lymphangioleiomyomatosis (LAM) develop pulmonary cysts associated with neoplastic, smooth muscle-like cells that feature neuroendocrine cell markers. The disease preferentially affects premenopausal women. Existing therapeutics do not cure LAM. As gp100 is a diagnostic marker expressed by LAM lesions, we proposed to target this immunogenic glycoprotein using TCR transgenic T cells. To reproduce the genetic mutations underlying LAM, we cultured Tsc2^-/- kidney tumor cells from aged Tsc2 heterozygous mice and generated a stable gp100-expressing cell line by lentiviral transduction. T cells were isolated from major histocompatibility complex-matched TCR transgenic pmel-1 mice to measure cytotoxicity in vitro, and 80% cytotoxicity was observed within 48 hours. Antigen-specific cytotoxicity was likewise observed using pmel-1 TCR-transduced mouse T cells, suggesting that transgenic T cells may likewise be useful to treat LAM in vivo. On intravenous injection, slow-growing gp100⁺ LAM-like cells formed lung nodules that were readily detectable in severe combined immunodeficient/beige mice. Adoptive transfer of gp100-reactive but not wild-type T cells into mice significantly shrunk established lung tumors, even in the absence of anti-PD-1 therapy. These results demonstrate the treatment potential of adoptively transferred T cells to eliminate pulmonary lesions in LAM.

A Self-Delivery Chimeric Peptide for Photodynamic Therapy Amplified Immunotherapy

In this paper, a self-delivery chimeric peptide PpIX-PEG₈ -KVPRNQDWL is designed for photodynamic therapy (PDT) amplified immunotherapy against malignant melanoma. After self-assembly into nanoparticles (designated as PPMA), this self-delivery system shows high drug loading rate, good dispersion, and stability as well as an excellent capability in producing reactive oxygen species (ROS). After cellular uptake, the ROS generated under light irradiation could induce the apoptosis and/or necrosis of tumor cells, which would subsequently stimulate the anti-tumor immune response. On the other hand, the melanoma specific antigen (KVPRNQDWL) peptide could also activate the specific cytotoxic T cells for anti-tumor immunity. Compared to immunotherapy alone, the combined photodynamic immunotherapy exhibits significantly enhanced inhibition of melanoma growth. Both in vitro and in vivo investigations confirm that PDT of PPMA has a positive effect on anti-tumor immune response. This self-delivery system demonstrates a great potential of this PDT amplified immunotherapy strategy for advanced or metastatic tumor treatment.

Viral-mimicking protein nanoparticle vaccine for eliciting anti-tumor responses

The immune system is a powerful resource for the eradication of cancer, but to overcome the low immunogenicity of tumor cells, a sufficiently strong CD8(+) T cell-mediated adaptive immune response is required. Nanoparticulate biomaterials represent a potentially effective delivery system for cancer vaccines, as they can be designed to mimic viruses, which are potent inducers of cellular immunity. We have been exploring the non-viral pyruvate dehydrogenase E2 protein nanoparticle as a biomimetic platform for cancer vaccine delivery. Simultaneous conjugation of a melanoma-associated gp100 epitope and CpG to the E2 nanoparticle (CpG-gp-E2) yielded an antigen-specific increase in the CD8(+) T cell proliferation index and IFN-γ secretion by 1.5-fold and 5-fold, respectively, compared to an unbound peptide and CpG formulation. Remarkably, a single nanoparticle immunization resulted in a 120-fold increase in the frequency of melanoma epitope-specific CD8(+) T cells in draining lymph nodes and a 30-fold increase in the spleen, relative to free peptide with free CpG. Furthermore, in the very aggressive B16 melanoma murine tumor model, prophylactic immunization with CpG-gp-E2 delayed the onset of tumor growth by approximately 5.5 days and increased animal survival time by approximately 40%, compared to PBS-treated animals. These results show that by combining optimal particle size and simultaneous co-delivery of molecular vaccine components, antigen-specific anti-tumor immune responses can be significantly increased.

The promise of combining radiation therapy and immunotherapy: morbidity and toxicity

ABSTRACT 

Radiation therapy and immunotherapy in partnership may have the capability of delivering a therapeutic effect exceeding the sum of its parts. The possible relationship has been demonstrated in murine models and has been extended to a variety of clinical trials. Though the standard notion of whole body radiation therapy is immunosuppressive, there is growing evidence toward the contrary for focal radiation therapy. Furthermore, if immunotherapeutic techniques can retune the immune system against cancerous cells, they should have obvious benefits for advanced treatments moving forward. Herein, we explore the promise in combining radiation therapy and immunotherapy with distinct focus on potential morbidities and toxicities through analysis of completed clinical trials.

Stem memory T cells (TSCM)-their role in cancer and HIV immunotherapies

Stem memory T cells (TSCM) have been described in mice, non-human primates and in humans, constituting approximately 2-4% of the total CD4(+) and CD8(+) T-cell population in the periphery. TSCM represent the earliest and long-lasting developmental stage of memory T cells, displaying stem cell-like properties, and exhibiting a gene profile between naïve and central memory T cells. Their self-renewal capacity and long-term survival has sparked interest in the cancer and human immunodeficiency virus (HIV) fields. How and when the formation of TSCM occurs during the immune response to pathogens and the therapeutic potential of these cells are currently being investigated. This review will explore the potential role of TSCM to be used as, or targeted by, immunotherapies and vaccines for treatment of cancer and HIV.

SOCS1 prevents potentially skin-reactive cytotoxic T lymphocytes from gaining the ability to cause inflammatory lesions

Suppressor of cytokine signaling 1 (SOCS1) is a critical regulator of T lymphocyte homeostasis. SOCS1-deficient mice accumulate CD8(+) T cells, which display a memory-like phenotype and proliferate strongly to IL-15. Socs1(-/-) mice develop inflammatory skin lesions, however, the underlying mechanisms are not well understood. In order to investigate the role of SOCS1 in regulating CD8(+) T cells potentially reactive to tissue antigens (Ags) of the skin, we generated Socs1(-/-) mice expressing MHC-I-restricted Pmel-1 transgenic TCR specific to the melanoma-derived gp100 Ag, which is also expressed by normal melanocytes. Socs1(-/-) Pmel-1 cells express increased levels of memory markers CD44, Ly6C, CD122, and CD62L, and show downregulation of TCR and upregulation of CD5, suggesting in vivo TCR stimulation. However, stimulation of Socs1(-/-)Pmel-1 cells with gp100-derived peptide induced only marginal proliferation in vitro despite eliciting strong effector functions, which was associated with elevated Blimp-1 induction. Following adoptive transfer to Rag1(-/-) mice, Socs1(-/-)Pmel-1 cells underwent lymphopenia-induced proliferation and caused severe skin pathology characterized by inflammatory lesions in ears, muzzle, extremities, and eyes. These findings underscore the importance of SOCS1 in regulating potentially skin-reactive cytotoxic T lymphocytes, which could get activated under conditions that promote Ag-nonspecific, cytokine-driven proliferation.

Combined stimulation of TLR9 and 4.1BB augments Trp2 peptide vaccine-mediated melanoma rejection by increasing Ag-specific CTL activity and infiltration into tumor sites

Peptide vaccines are a clinically applicable therapy shown to be effective in tumor control. In this study, Trp2 peptides plus CpG-oligodeoxynucleotide treatment was found to induce Ag-specific IFN-γ and CD8+CTL responses, and antitumor activity against large established melanoma (tumor size, 7mm). A combination of anti-4.1BB antibodies with Trp2 peptides+CpG-oligodeoxynucleotide increased the antitumor cure rate from 0% to 75%. This effect was concomitant with greater induction of Ag-specific CD8+CTLs and their infiltration into the tumor sites, highlighting the importance of combined stimulation of TLR9 and 4.1BB for achieving tumor eradication. These findings may have implications for designing peptide-based therapeutic vaccines for cancer-patients.

Clinical opportunities in combining immunotherapy with radiation therapy

Preclinical work in murine models suggests that local radiotherapy plus intratumoral syngeneic dendritic cells (DC) injection can mediate immunologic tumor eradication. Radiotherapy affects the immune response to cancer, besides the direct impact on the tumor cells, and other ways to coordinate immune modulation with radiotherapy have been explored. We review here the potential for immune-mediated anticancer activity of radiation on tumors. This can be mediated by differential antigen acquisition and presentation by DC, through changes of lymphocytes' activation, and changes of tumor susceptibility to immune clearance. Recent work has implemented the combination of external beam radiation therapy (EBRT) with intratumoral injection of DC. This included a pilot study of coordinated intraprostatic, autologous DC injection together with radiation therapy with five HLA-A2(+) subjects with high-risk, localized prostate cancer; the protocol used androgen suppression, EBRT (25 fractions, 45 Gy), DC injections after fractions 5, 15, and 25, and then interstitial radioactive implant. Another was a phase II trial using neo-adjuvant apoptosis-inducing EBRT plus intra-tumoral DC in soft tissue sarcoma, to test if this would increase immune activity toward soft tissue sarcoma associated antigens. In the future, radiation therapy approaches designed to optimize immune stimulation at the level of DC, lymphocytes, tumor and stroma effects could be evaluated specifically in clinical trials.

Intratumoral electroporation of IL-12 cDNA eradicates established melanomas by Trp2(180-188)-specific CD8+ CTLs in a perforin/granzyme-mediated and IFN-γ-dependent manner: application of Trp2(180-188) peptides

Intratumoral electroporation (IT-EP) with IL-12 cDNA (IT-EP/IL12) can lead to the eradication of established B16 melanoma tumors in mice. Here, we explore the immunological mechanism of the antitumor effects generated by this therapy. The results show that IT-EP/IL12 applied only once resulted in eradication in 70% animals with large established B16 tumors. Tumor eradication required the participation of CD8+ T cells, but not CD4+ T cells and NK cells. IT-EP/IL12 induced antigen-specific CD8+ T cell responses against the immunodominant Trp2(180-188) epitope and generated a systemic response, resulting in significant therapeutic effects against distal, untreated tumors. The therapeutic effect of IT-EP/IL12 was absent in perforin-deficient mice, indicating that tumor elimination occurred through conventional perforin/granzyme lysis by CTLs. Moreover, this therapy induced some degree of immunological memory that protected approximately one-third of the cured mice against a subsequent tumor challenge. Moreover, antitumor efficacy and long-term protection against B16 were significantly improved by concurrent Trp2 peptide immunization through more induction of Ag-specific CTL responses and more attraction of IFN-γ-expressing CD8+ T cells into tumor sites. The antitumor effect of IT-EP/IL12 required the participation of IFN-γ, which was shown to induce MHC class I expression on B16 cells and increase the lytic activity of the CD8+ CTL generated by IT-EP/IL12. The results from these animal studies may help in the development of IT-EP/IL12 for cancer patients.

Serial assessment of lymphocytes and apoptosis in the prostate during coordinated intraprostatic dendritic cell injection and radiotherapy

Local radiotherapy plus intratumoral syngeneic dendritic cell injection can mediate apoptosis/cell death and immunological tumor eradication in murine models. A novel method of coordinated intraprostatic, autologous dendritic cell injection together with radiation therapy was prospectively evaluated in five HLA-A2(+) subjects with high-risk, localized prostate cancer, using androgen suppression, 45 Gy external beam radiation therapy in 25 fractions over 5 weeks, dendritic cell injections after fractions 5, 15 and 25 and then interstitial radioactive seed placement. Serial prostate biopsies before and during treatment showed increased apoptotic cells and parenchymal distribution of CD8(+) cells. CD8(+) T-cell responses to test peptides were assessed using an enzyme-linked immunosorbent spot IFN-γ production assay, demonstrating some prostate cancer-specific protein-derived peptides associated with increased titer. In conclusion, the technique was feasible and well-tolerated and specific immune responses were observable. Future trials could further test the utility of this approach and improve on temporal coordination of intratumoral dendritic cell introduction with particular timelines of therapy-induced apoptosis.

MHC-class I-restricted CD4 T cells: a nanomolar affinity TCR has improved anti-tumor efficacy in vivo compared to the micromolar wild-type TCR

Clinical studies with immunotherapies for cancer, including adoptive cell transfers of T cells, have shown promising results. It is now widely believed that recruitment of CD4(+) helper T cells to the tumor would be favorable, as CD4(+) cells play a pivotal role in cytokine secretion as well as promoting the survival, proliferation, and effector functions of tumor-specific CD8(+) cytotoxic T lymphocytes. Genetically engineered high-affinity T-cell receptors (TCRs) can be introduced into CD4(+) helper T cells to redirect them to recognize MHC-class I-restricted antigens, but it is not clear what affinity of the TCR will be optimal in this approach. Here, we show that CD4(+) T cells expressing a high-affinity TCR (nanomolar K (d) value) against a class I tumor antigen mediated more effective tumor treatment than the wild-type affinity TCR (micromolar K (d) value). High-affinity TCRs in CD4(+) cells resulted in enhanced survival and long-term persistence of effector memory T cells in a melanoma tumor model. The results suggest that TCRs with nanomolar affinity could be advantageous for tumor targeting when expressed in CD4(+) T cells.

The Florida Melanoma Trial I: A Prospective Multicenter Phase I/II Trial of Postoperative Hypofractionated Adjuvant Radiotherapy with Concurrent Interferon-Alfa-2b in the Treatment of Advanced Stage III Melanoma with Long-Term Toxicity Follow-Up

Radiotherapy (RT) and interferon-alfa-2b (IFN α-2b) have individually been used for adjuvant therapy stage III melanoma with high-risk pathologic features. We hypothesized that concurrent adjuvant RT and IFN α-2b may decrease the risk of regional recurrence following surgery with acceptable toxicity. A prospective multicenter phase I/II study was conducted to evaluate hypofractionated RT with concurrent IFN. Induction IFN α-2b, 20 MU/m2/d, was administered IV ×5 consecutive days every week for 4 weeks. Next, RT 30 Gy in 5 fractions was given with concurrent IFN α-2b, 10 MU/m2 SQ 3 times per week on days alternating with RT. Subsequent maintenance therapy consisted of adjuvant IFN α-2b, 10 MU/m2 SQ 3 times per week to a total of 1 year. To fully evaluate patterns of failure, long-term follow-up was conducted for up to 10 years. A total of 29 consenting patients were enrolled between August 1997 and March 2000. The maximum (worst) grade of acute nonhematologic toxicity during concurrent RT/IFN α-2b (and up to 2 weeks post RT) was grade 3 skin toxicity noted in 2 patients (9%). Late effects were limited. Probability of regional control was 78% (95% CI: 55%–90%) at 12 months. The median follow-up (range) was 80 (51–106) months among ten survivors (43%). The median overall survival was 34.5 months while the median failure-free survival was 19.9 months. Postoperative concurrent hypofractionated RT with IFN α-2b for advanced stage III melanoma appears to be associated with acceptable toxicity and may provide reasonable in-field control in patients at high risk of regional failure.

Murine rhabdomyosarcoma is immunogenic and responsive to T-cell-based immunotherapy

BACKGROUND

Immunotherapies targeting cellular immunity are currently approved for treatment of melanoma, renal cell carcinoma, and prostate cancer. Studies on the immunogenicity and immune responsiveness of pediatric tumors are limited, therefore, it remains unclear to what extent T-cell-based immunotherapy holds promise for pediatric solid tumors.

PROCEDURE

A new rhabdomyosarcoma cell line (M3-9-M) was derived from an embryonal rhabdomyosarcoma (ERMS) occurring in a C57BL/6 mouse transgenic for hepatocyte growth factor and heterozygous for mutated p53. Primary tumors and metastases derived from M3-9-M were studied for similarities to human ERMS, and for immunogenicity and immune responsiveness.

RESULTS

Primary and metastatic tumors develop after orthotopic injection of M3-9-M into immunocompetent C57BL/6 mice, which mirror human ERMS with regard to histology, gene expression, and metastatic behavior. Whole cell vaccination using irradiated M3-9-M cells or M3-9-M-pulsed dendritic cells (DC)-induced tumor-specific T-cell responses that prevent tumor growth following low-dose tumor injection, and slow tumor growth following higher doses. Administration of anti-CD25 moAbs to deplete CD4(+)CD25(+)FOXP3(+) regulatory T cells prior to tumor vaccination enhanced the potency of the ERMS tumor vaccine. Adoptive immunotherapy with M3-9-M primed T cells plus DC-based vaccination resulted in complete eradication of day 10 M3-9-M derived tumors.

CONCLUSIONS

M3-9-M derived murine ERMS is immunogenic and immunoresponsive; regulatory T cells contribute to immune evasion by murine rhabdomyosarcoma. Adoptive immunotherapy with DC vaccination can eradicate low tumor burdens. Future work will seek to identify the tumor-associated antigens that mediate protective and therapeutic immunity in this model.

The confluence of stereotactic ablative radiotherapy and tumor immunology

Stereotactic radiation approaches are gaining more popularity for the treatment of intracranial as well as extracranial tumors in organs such as the liver and lung. Technology, rather than biology, is driving the rapid adoption of stereotactic body radiation therapy (SBRT), also known as stereotactic ablative radiotherapy (SABR), in the clinic due to advances in precise positioning and targeting. Dramatic improvements in tumor control have been demonstrated; however, our knowledge of normal tissue biology response mechanisms to large fraction sizes is lacking. Herein, we will discuss how SABR can induce cellular expression of MHC I, adhesion molecules, costimulatory molecules, heat shock proteins, inflammatory mediators, immunomodulatory cytokines, and death receptors to enhance antitumor immune responses.

Changes in dendritic cell phenotype after a new high-dose weekly schedule of interleukin-2 therapy for kidney cancer and melanoma

High-dose intravenous interleukin-2 (IL-2) therapy (14 doses/course, 2 courses/cycle) for metastatic melanoma or kidney cancer induces infrequent, although major responses. In this trial, we evaluated a new schedule (dose of 600,000 IU/kg, 8 h between doses, 5 doses/course, 4 courses at weekly intervals/cycle) of high-dose IL-2, in which we inserted more planned breaks while maintaining high cumulative dose delivery, and investigated the relationship between dendritic cells (DC) and response to treatment. Target dose delivery was attained: median IL-2 cumulative dose per patient was 11.4 and 10.8 million units/kg (cycles 1 and 2, respectively). Major responses were observed in patients with kidney cancer (n=20; 3 complete and 2 partial responses) and melanoma (n=16; 1 partial response). Adverse events appeared comparable with those typically associated with high-dose IL-2. From this data set, we introduce the hypothesis-generating observation that patients who had more favorable outcomes had high pretreatment DC-to-myeloid-derived suppressor cell (MDSC) ratios, similar to the ratio observed in healthy individuals. However, even in patients with the most favorable outcome, after treatment, there were IL-2-induced changes in the DC-to-MDSC ratio, specifically increases in MDSCs. This modified IL-2 schedule is a feasible option, with a more uniform dose delivery over the treatment cycle, a similar toxicity profile, and observed complete, durable response in patients with renal cancer. Pretreatment assessment of DC phenotypic or maturational status may be a starting point to predicting response to high-dose IL-2 cytokine immunotherapy in patients with melanoma and kidney cancer.

Adoptive immunotherapy combined with intratumoral TLR agonist delivery eradicates established melanoma in mice

Toll-like receptor (TLR) agonists can trigger broad inflammatory responses that elicit rapid innate immunity and promote the activities of lymphocytes, which can potentially enhance adoptive immunotherapy in the tumor-bearing setting. In the present study, we found that Polyinosinic:Polycytidylic Acid [Poly(I:C)] and CpG oligodeoxynucleotide 1826 [CpG], agonists for TLR 3 and 9, respectively, potently activated adoptively transferred T cells against a murine model of established melanoma. Intratumoral injection of Poly(I:C) and CpG, combined with systemic transfer of activated pmel-1 T cells, specific for gp100(25-33), led to enhanced survival and eradication of 9-day established subcutaneous B16F10 melanomas in a proportion of mice. A series of survival studies in knockout mice supported a key mechanistic pathway, whereby TLR agonists acted via host cells to enhance IFN-γ production by adoptively transferred T cells. IFN-γ, in turn, enhanced the immunogenicity of the B16F10 melanoma line, leading to increased killing by adoptively transferred T cells. Thus, this combination approach counteracted tumor escape from immunotherapy via downregulation of immunogenicity. In conclusion, TLR agonists may represent advanced adjuvants within the setting of adoptive T-cell immunotherapy of cancer and hold promise as a safe means of enhancing this approach within the clinic.

Improving adoptive T cell therapy by targeting and controlling IL-12 expression to the tumor environment

Interleukin-12 (IL-12) is an important immunostimulatory cytokine, yet its clinical application has been limited by the systemic toxicity associated with its administration. In this work, we developed a strategy to selectively deliver IL-12 to the tumor environment using genetically engineered lymphocytes. However, peripheral blood lymphocytes (PBLs) transduced with a γ-retroviral vector, which constitutively expressed IL-12, failed to expand in culture due to apoptosis. To circumvent this problem, a vector was designed where IL-12 expression was directed by a composite promoter-containing binding motifs for nuclear factor of activated T-cells (NFAT.hIL12.PA2). The NFAT-responsive promoter was activated to drive IL-12 expression upon the recognition of tumor-specific antigen mediated by a T cell receptor (TCR) that was engineered into the same lymphocytes. We tested the efficacy of the inducible IL-12 vector in vivo in a murine melanoma model. Adoptive transfer of pmel-1 T cells genetically engineered with NFAT-murineIL12 (NFAT.mIL12.PA2) significantly enhanced regression of large established B16 melanoma. Notably, this targeted and controlled IL-12 treatment was without toxicity. Taken together, our results suggest that using the NFAT.hIL12.PA2 vector might be a promising approach to enhance adoptive cancer immunotherapy.

Archaeosome adjuvant overcomes tolerance to tumor-associated melanoma antigens inducing protective CD8 T cell responses

Vesicles comprised of the ether glycerolipids of the archaeon Methanobrevibacter smithii (archaeosomes) are potent adjuvants for evoking CD8⁺ T cell responses. We therefore explored the ability of archaeosomes to overcome immunologic tolerance to self-antigens. Priming and boosting of mice with archaeosome-antigen evoked comparable CD8⁺ T cell response and tumor protection to an alternate boosting strategy utilizing live bacterial vectors for antigen delivery. Vaccination with melanoma antigenic peptides TRP_181-189 and Gp100_25-33 delivered in archaeosomes resulted in IFN-γ producing antigen-specific CD8⁺ T cells with strong cytolytic capability and protection against subcutaneous B16 melanoma. Targeting responses against multiple antigens afforded prolonged median survival against melanoma challenge. Entrapment of multiple peptides within the same vesicle or admixed formulations were both effective at evoking CD8⁺ T cells against each antigen. Melanoma-antigen archaeosome formulations also afforded therapeutic protection against established B16 tumors when combined with depletion of T-regulatory cells. Overall, we demonstrate that archaeosome adjuvants constitute an effective choice for formulating cancer vaccines.

Combining carbon ion radiotherapy and local injection of α-galactosylceramide-pulsed dendritic cells inhibits lung metastases in an in vivo murine model

PURPOSE

Our previous report indicated that carbon ion beam irradiation upregulated membrane-associated immunogenic molecules, underlining the potential clinical application of radioimmunotherapy. The antimetastatic efficacy of local combination therapy of carbon ion radiotherapy and immunotherapy was examined by use of an in vivo murine model.

METHODS AND MATERIALS

Tumors of mouse squamous cell carcinoma (NR-S1) cells inoculated in the legs of C3H/HeSlc mice were locally irradiated with a single 6-Gy dose of carbon ions (290 MeV/nucleon, 6-cm spread-out Bragg peak). Thirty-six hours after irradiation, α-galactosylceramide-pulsed dendritic cells (DCs) were injected into the leg tumor. We investigated the effects on distant lung metastases by counting the numbers of lung tumor colonies, making pathologic observations, and assessing immunohistochemistry.

RESULTS

The mice with no treatment (control) presented with 168 ± 53.8 metastatic nodules in the lungs, whereas the mice that received the combination therapy of carbon ion irradiation and DCs presented with 2.6 ± 1.9 (P = 0.009) at 2 weeks after irradiation. Immunohistochemistry showed that intracellular adhesion molecule 1, which activates DCs, increased from 6 h to 36 h after irradiation in the local tumors of the carbon ion-irradiated group. The expression of S100A8 in lung tissue, a marker of the lung pre-metastatic phase, was decreased only in the group with a combination of carbon ions and DCs.

CONCLUSIONS

The combination of carbon ion radiotherapy with the injection of α-galactosylceramide-pulsed DCs into the primary tumor effectively inhibited distant lung metastases.

Nonsurgical options for hepatocellular carcinoma: evolving role of external beam radiotherapy

BACKGROUND

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide and thus poses a global concern. Its incidence is expected to increase in North America secondary to the increasing incidence of patients who develop hepatitis C. Patients who ultimately develop cirrhosis have an increased risk of developing hepatocellular carcinoma.

METHODS

The authors focus on nonsurgical therapies for this disease with an exploration of how external beam radiotherapy can be used alone or with other modalities. The development of partial liver strategies secondary to an explosion in radiation treatment planning and delivery advances is reviewed. Integration of advanced technology has evolved from three-dimensional conformal treatment to intensity-modulated radiation therapy and image-guided radiation therapy, along with stereotactic body radiation therapy, tomotherapy, and proton beam therapy.

RESULTS

Current data show a promising future for treatment strategies incorporating radiation with high rates of infield tumor control and low rates of radiation-induced liver disease. Radiation can be delivered in conjunction with transarterial catheter embolization for advanced-stage patients. External beam radiotherapy also has a role in the setting of patients with macrovascular tumor thrombus.

CONCLUSIONS

Future directions include how to best synergize the effects of radiation strategies with novel agents, given the hypervascularity of HCC. Downstaging of larger lesions with these therapies to resectable or transplantable disease may lead to better outcomes for patients deemed inoperable at diagnosis, and definitive radiotherapy may offer cure to patients with smaller lesions.

Systemic therapy for advanced hepatocellular carcinoma: past, present, and future

BACKGROUND

Although approximately 80% of hepatocellular carcinoma (HCC) cases occur in developing countries, the incidence of HCC in Western countries is on the rise due to the impact of hepatitis C. Challenges in developing effective therapies include the inherent chemoresistance of HCC, the pharmacologic challenges presented by a diseased liver, the presentation of most patients at advanced stages, and the difficulty in adequately measuring radiological response. While responses to traditional chemotherapeutic agents have been documented, significant survival benefit is debatable.

METHODS

The authors review the results of published clinical trials of systemic therapy and immunotherapy that have impacted the present treatment of HCC.

RESULTS

With recent progress in the elucidation of HCC molecular pathways, targeted agents show promise. The multikinase inhibitor sorafenib has provided survival benefit in patients with advanced HCC and well-preserved liver function. Sunitinib, bevacizumab, epidermal growth factor receptor inhibitors, and mammalian target of rapamycin (mTOR) inhibitors have shown activity in small patient cohorts. Immunotherapy appears to be a promising approach that can result in the regression of bulky, invasive cancer in some patients.

CONCLUSIONS

New agents with a variety of mechanisms of activity offer promising therapeutic options for patients with advanced HCC.

Cyclophosphamide induces bone marrow to yield higher numbers of precursor dendritic cells in vitro capable of functional antigen presentation to T cells in vivo

We have shown recently that cyclophosphamide (CTX) treatment induced a marked increase in the numbers of immature dendritic cells (DCs) in blood, coinciding with enhanced antigen-specific responses of the adoptively transferred CD8(+) T cells. Because this DC expansion was preceded by DC proliferation in bone marrow (BM), we tested whether BM post CTX treatment can generate higher numbers of functional DCs. BM was harvested three days after treatment of C57BL/6 mice with PBS or CTX and cultured with GM-CSF/IL-4 in vitro. Compared with control, BM from CTX-treated mice showed faster generation and yielded higher numbers of DCs with superior activation in response to toll-like receptor (TLR) agonists. Vaccination with peptide-pulsed DCs generated from BM from CTX-treated mice induced comparable adjuvant effects to those induced by control DCs. Taken together, post CTX BM harbors higher numbers of DC precursors capable of differentiating into functional DCs, which be targeted to create host microenvironment riches in activated DCs upon treatment with TLR agonists.

Immunotherapy for human renal cell carcinoma by adoptive transfer of autologous transforming growth factor beta-insensitive CD8+ T cells

PURPOSE

Transforming growth factor-beta (TGF-beta) is a potent immunosuppressor that has been associated with tumor evasion from the host immune surveillance and, thus, tumor progression. We tested a novel immunotherapy for human renal cell cancer (RCC) using a technique that involves the adoptive transfer of autologous tumor-reactive, TGF-beta-insensitive CD8(+) T cells into human RCC-challenged immunodeficient mice to identify its potent antitumor responses.

EXPERIMENTAL DESIGN

The present study was conducted using a one-to-one adoptive transfer strategy to treat tumor-bearing severe combined immunodeficient (SCID/beige) mouse. The SCID/beige mice were humanized with peripheral blood mononuclear cells from patients with RCC (Hu-PBMC-SCID) before adoptive transfer. Autologous CD8(+) T cells were expanded ex vivo using autologous patient's dendritic cells pulsed with the tumor lysate and rendered TGF-beta insensitive by dominant-negative TGF-beta type II receptor. In addition, human RCC cell lines were generated using patients' tumor cells injected into SCID/beige mice.

RESULTS

Using flow cytometry analysis, we confirmed the expression of the tumor-reactive, TGF-beta-insensitive CD8(+) T cells were the effector CD8(+) cells (CD27(-)CDRA(+)). Adoptive transfer of autologous TGF-beta-insensitive CD8(+) T cells into tumor-bearing Hu-PBMC-SCID mice induced robust tumor-specific CTL responses in vitro, were associated with tumor apoptosis, suppressed lung metastasis, and prolonged survival times in vivo.

CONCLUSION

The one-to-one adoptive transfer strategy is an ideal in vivo murine model for studying the relationship between TGF-beta and immunosurveillance in RCC in vivo. Furthermore, this technique may offer the promise of a novel therapeutic option for the treatment of human patients with RCC.

Nanoparticle-delivered multimeric soluble CD40L DNA combined with Toll-Like Receptor agonists as a treatment for melanoma

Stimulation of CD40 or Toll-Like Receptors (TLR) has potential for tumor immunotherapy. Combinations of CD40 and TLR stimulation can be synergistic, resulting in even stronger dendritic cell (DC) and CD8+ T cell responses. To evaluate such combinations, established B16F10 melanoma tumors were injected every other day X 5 with plasmid DNA encoding a multimeric, soluble form of CD40L (pSP-D-CD40L) either alone or combined with an agonist for TLR1/2 (Pam₃CSK₄ ), TLR2/6 (FSL-1 and MALP2), TLR3 (polyinosinic-polycytidylic acid, poly(I:C)), TLR4 ( monophosphoryl lipid A, MPL), TLR7 (imiquimod), or TLR9 (Class B CpG phosphorothioate oligodeoxynucleotide, CpG). When used by itself, pSP-D-CD40L slowed tumor growth and prolonged survival, but did not lead to cure. Of the TLR agonists, CpG and poly(I:C) also slowed tumor growth, and the combination of these two TLR agonists was more effective than either agent alone. The triple combination of intratumoral pSP-D-CD40L + CpG + poly(I:C) markedly slowed tumor growth and prolonged survival. This treatment was associated with a reduction in intratumoral CD11c+ dendritic cells and an influx of CD8+ T cells. Since intratumoral injection of plasmid DNA does not lead to efficient transgene expression, pSP-D-CD40L was also tested with cationic polymers that form DNA-containing nanoparticles which lead to enhanced intratumoral gene expression. Intratumoral injections of pSP-D-CD40L-containing nanoparticles formed from polyethylenimine (PEI) or C32 (a novel biodegradable poly(B-amino esters) polymer) in combination with CpG + poly(I:C) had dramatic antitumor effects and frequently cured mice of B16F10 tumors. These data confirm and extend previous reports that CD40 and TLR agonists are synergistic and demonstrate that this combination of immunostimulants can significantly suppress tumor growth in mice. In addition, the enhanced effectiveness of nanoparticle formulations of DNA encoding immunostimulatory molecules such as multimeric, soluble CD40L supports the further study of this technology for tumor immunotherapy.

Evidence of systemic Th2-driven chronic inflammation in patients with metastatic melanoma

PURPOSE

Immunotherapeutic modalities are commonly used for treatment of patients with melanoma. The therapeutic success in preclinical models has not yielded the expected clinical results. To understand this discrepancy, we attempted to define immune homeostasis of 209 patients with melanoma across stages of disease relative to normal controls.

EXPERIMENTAL DESIGN

Peripheral blood mononuclear cells (PBMC) and plasma were collected from patients and healthy donors. PBMC were analyzed for frequencies of natural killer, dendritic, and T cells and their functional status. Matched plasma samples were analyzed for the concentrations of 27 cytokines, chemokines, and growth factors. RNA was isolated from 24 metastatic melanoma tumor biopsies and profiled by microarray analysis.

RESULTS

The frequency of natural killer, T, and dendritic cells in patients does not significantly change across stages of melanoma. However, plasma concentrations of Th2 cytokines [interleukin (IL)-4, IL-5, IL-10, and IL-13] in tumor-bearing patients were significantly higher than those with resected melanoma. Expression array analysis of metastatic melanoma revealed that the malignant melanocytes were not the source of the Th2 cytokines but did highly up-regulate vascular endothelial growth factor (VEGF) transcripts, consistent with plasma VEGF concentrations. In vitro VEGF exposure of normal PBMC lead to repolarization from Th1 to Th2 emulating the state of metastatic melanoma.

CONCLUSIONS

Patients with metastatic melanoma exist in a state of Th2-mediated "chronic inflammation" as a result of at least VEGF overproduction by malignant tumors. These data support prior observations regarding the effect of VEGF on immune cell function and suggests consideration of VEGF inhibitors in future cancer immunotherapy clinical studies in metastatic melanoma.

Immunotherapy for advanced melanoma

Immunotherapy for melanoma has undergone significant change since the first attempts to treat patients with high dose IL-2. Herein, strategies to boost patient antitumor immunity through vaccination, treatment with agents that augment host immunity, and adoptive cell transfer will be discussed. The first two strategies have yielded only limited clinical success, but adoptive cell transfer therapy, particularly following a lymphodepleting, preconditioning regimen has resulted in objective response rates approaching 50%. For a number of reasons, lymphodepletion appears to be critical for maintenance of circulating antitumor T cells following adoptive cell transfer. Balancing antitumor efficacy, autoimmunity, and reconstitution of a functioning immune system remain challenging and potentially life-threatening issues.

"It is the antigen(s), stupid" and other lessons from over a decade of vaccitherapy of human cancer

The lessons are: (a) human cancers certainly respond to immunological manipulations. Efforts at human cancer immunotherapy are therefore worthwhile. (b) Prophylaxis is very different from therapy of pre-existing disease, and hence much enthusiasm should not be derived from successful prophylaxis studies. Even in case of infectious agents against which robust prophylaxis is routinely achieved, therapy is nearly impossible once the disease has established. (c) Studies with appropriate cancer models of mice and rats are useful. The notion that it is easy to cure cancers in mice is generally advanced the most confidently by those who have never cured a mouse of cancer by immunotherapy. (d) With a nod to James Carville, it is the antigen(s), stupid! We still do not know the identity of protective tumor antigens. If any lesson can be drawn at all, it may well be that cancer immunotherapy must move away from the one-shoe-fits-all therapeutic models of chemotherapy and must move to individualized approaches. (e) All targets are equal, but some are more equal than others. The key is specificity for cancer. That does not necessarily mean specificity for cancer cells. (f) Vaccitherapy must be attempted preferably in the minimal residual disease setting, even though this is certain to be time-taking and expensive. In the setting of bulky disease, vaccitherapy must be combined with blockade of inhibitory signals, or depletion of down-regulatory T cells. Inhibition of effector level suppression of immune response is a key. Vaccitherapy alone or immuno-modulation alone is unlikely to succeed in therapy of bulky metastatic disease.

Novel translational strategies in colorectal cancer research

Defining translational research is still a complex task. In oncology, translational research implies using our basic knowledge learnt from in vitro and in vivo experiments to directly improve diagnostic tools and therapeutic approaches in cancer patients. Moreover, the better understanding of human cancer and its use to design more reliable tumor models and more accurate experimental systems also has to be considered a good example of translational research. The identification and characterization of new molecular markers and the discovery of novel targeted therapies are two main goals in colorectal cancer translational research. However, the straightforward translation of basic research findings, specifically into colorectal cancer treatment and vice versa is still underway. In the present paper, a summarized view of some of the new available approaches on colorectal cancer translational research is provided. Pros and cons are discussed for every approach exposed.

Cooperation between CD4 and CD8 T cells for anti-tumor activity is enhanced by OX40 signals

The relative contribution of OX40 (CD134) to priming of CD8 T cells in complex systems where CD4 and CD8 cells respond and cooperate together is not clear. We previously found that OX40 expressed on tumor-reactive CD8 T cells controls their initial persistence when adoptively transferred in vivo and is required for delayed tumor growth. We now show that exogenous stimulation of OX40 with agonist antibody augments its ability to suppress the growth of new as well as established tumors, correlating with marked expansion of adoptively transferred CD8 T cells. Concomitantly, anti-OX40 strongly enhanced the number of tumor antigen-reactive CD4 T cells. Moreover, the augmented accumulation of CD8 T cells was prevented in animals lacking MHC class II or depleted of CD4 cells and did not occur in OX40-deficient animals receiving wild-type CD8 cells, demonstrating that non-CD8 cells are the major target of OX40 signals. These results suggest that while OX40 signaling to a CD8 T cell can control its expansion, OX40 expressed on non-CD8 cells strongly influences CD8 priming and in vivo activity. OX40 therefore represents an important signal for allowing effective cooperation between CD4 and CD8 cells and for promoting cell interplay and tumor rejection where CD8 activity is limiting.

The merits of in vitro versus in vivo modeling in investigation of the immune system

Immunity is vital for determining self and for the recognition and swift eradication of foreign antigens without harming the host. Innate immunity developed in metazoan, multi-cellular organisms under overwhelming selection pressure of invasive microbes and, although imperfect, has performed admirably to enable the evolution of higher eukaryotes. Adaptive immunity developed within an existing innate immune system to more effectively eradicate foreign antigens, whether from pathogens, malignant cells, or microbial toxins, such that repeated stimulations with foreign antigens are more efficiently excluded. Investigation of the immune system requires both in vivo and in vitro experimentation, not only because of the inherent complexity of immunity and the required pertinence of using higher mammals to not falsely disrupt the immune system, but also to use isolates of the specific cellular and humoral components to determine function, signal transduction, and a possible role of these constituents without the complexity and redundancy of immunity in intact animals. The hypotheses of well-designed in vitro experiments must also be tested in intact in vivo models to determine relevance and to discard artifactual findings secondary to the in vitro environment. The following review outlines the basic constituents and functions of both adaptive and innate immunity to demonstrate the importance of both in vivo and in vitro investigation of immunity in our attempt to define host defense and to decrease morbidity and mortality in humans.

OX40 and Bcl-xL promote the persistence of CD8 T cells to recall tumor-associated antigen

The molecular signals that allow primed CD8 T cells to persist and be effective are particularly important during cancer growth. With response to tumor-expressed Ag following adoptive T cell transfer, we show that CD8 effector cells deficient in OX40, a TNFR family member, could not mediate short-term tumor suppression. OX40 was required at two critical stages. The first was during CD8 priming in vitro, in which APC-transmitted OX40 signals endowed the ability to survive when adoptively transferred in vivo before tumor Ag encounter. The second was during the in vivo recall response of primed CD8 T cells, the stage in which OX40 contributed to the further survival and accumulation of T cells at the tumor site. The lack of OX40 costimulation was associated with reduced levels of Bcl-x(L), and retroviral expression of Bcl-x(L) in tumor-reactive CD8 T cells conferred greatly enhanced tumor protection following adoptive transfer. These data demonstrate that OX40 and Bcl-x(L) can control survival of primed CD8 T cells and provide new insights into both regulation of CD8 immunity and control of tumors.

Complete protection against melanoma in absence of autoimmune depigmentation after rejection of melanoma cells expressing alpha(1,3)galactosyl epitopes

The major barrier for xenotransplantation in humans is the presence of alpha(1-3) Galactosyl epitopes (alphaGal) in xenogeneic tissue and the vast quantities of natural antibodies (Ab) produced by humans against this epitope. The binding of anti-alphaGal Ab to cells expressing alphaGal triggers a complement-mediated hyperacute rejection of target cells. The hyperacute rejection of whole cancer cells, modified to express alphaGal epitopes, could be exploited as a new cancer vaccine to treat human cancers. We tested this hypothesis in alphaGalactosyltransferase knockout (alphaGT KO) mice which, like humans, do not express alphaGal on their cell surfaces and can produce anti-alphaGal Ab. Forty-five percent of mice with preexisting anti-alphaGal Ab rejected alphaGal positive melanoma cells (B16alphaGal). These mice remained tumor-free for more than 90 days. The majority of control mice injected with B16Null, alphaGal negative cells succumbed to melanoma. The rejection of B16alphaGal induced strong long-lasting antitumor immunity against B16Null measured by the expansion of cytotoxic T lymphocytes. In addition, mice rejecting B16alphaGal were protected against melanoma since they survived a second rechallenge with B16Null. Protected mice developed antitumor immunity in the absence of autoimmune depigmentation (vitiligo). These results show that rejection of alphaGal positive melanoma cells can efficiently boost the immune response to other tumor associated antigens present in alphaGal negative melanoma cells. This study supports the concept of a novel anticancer vaccine to treat human malignancies.

Adoptive transfer of tumor-reactive transforming growth factor-beta-insensitive CD8+ T cells: eradication of autologous mouse prostate cancer

Transforming growth factor (TGF)-beta is a potent immunosuppressant. Overproduction of TGF-beta by tumor cells may lead to tumor evasion from the host immune surveillance and tumor progression. The present study was conducted to develop a treatment strategy through adoptive transfer of tumor-reactive TGF-beta-insensitive CD8+ T cells. The mouse TRAMP-C2 prostate cancer cells produced large amounts of TGF-beta1 and were used as an experimental model. C57BL/6 mice were primed with irradiated TRAMP-C2 cells. CD8+ T cells were isolated from the spleen of primed animals, were expanded ex vivo, and were rendered TGF-beta insensitive by infecting with a retrovirus containing dominant-negative TGF-beta type II receptor. Results of in vitro cytotoxic assay revealed that these CD8+ T cells showed a specific and robust tumor-killing activity against TRAMP-C2 cells but were ineffective against an irrelevant tumor line, B16-F10. To determine the in vivo antitumor activity, recipient mice were challenged with a single injection of TRAMP-C2 cells for a period up to 21 days before adoptive transfer of CD8+ T cells was done. Pulmonary metastasis was either eliminated or significantly reduced in the group receiving adoptive transfer of tumor-reactive TGF-beta-insensitive CD8+ T cells. Results of immunofluorescent studies showed that only tumor-reactive TGF-beta-insensitive CD8+ T cells were able to infiltrate into the tumor and mediate apoptosis in tumor cells. Furthermore, transferred tumor-reactive TGF-beta-insensitive CD8+ T cells were able to persist in tumor-bearing hosts but declined in tumor-free animals. These results suggest that adoptive transfer of tumor-reactive TGF-beta-insensitive CD8+ T cells may warrant consideration for cancer therapy.

Synergy of IL-21 and IL-15 in regulating CD8+ T cell expansion and function

Interleukin (IL)-21 is the most recently recognized of the cytokines that share the common cytokine receptor γ chain (γ_c), which is mutated in humans with X-linked severe combined immunodeficiency. We now report that IL-21 synergistically acts with IL-15 to potently promote the proliferation of both memory (CD44^high) and naive (CD44^low) phenotype CD8⁺ T cells and augment interferon-γ production in vitro. IL-21 also cooperated, albeit more weakly, with IL-7, but not with IL-2. Correspondingly, the expansion and cytotoxicity of CD8⁺ T cells were impaired in IL-21R^−/− mice. Moreover, in vivo administration of IL-21 in combination with IL-15 boosted antigen-specific CD8⁺ T cell numbers and resulted in a cooperative effect on tumor regression, with apparent cures of large, established B16 melanomas. Thus, our studies reveal that IL-21 potently regulates CD8⁺ T cell expansion and effector function, primarily in a synergistic context with IL-15.

Tumour-infiltrating gamma/delta T-lymphocytes are correlated with a brief disease-free interval in advanced ovarian serous carcinoma

BACKGROUND

Significant progress has been made in understanding the molecular biology of ovarian carcinoma. Along with the molecular characteristics of cancer, the patient's response to the tumour may also contribute to survival; in particular, the effect of the immune system may play an important role on survival of cancer patients.

PATIENTS AND METHODS

We analysed the CD3 positive tumour-infiltrating T cells and direct molecular assessment of T cell receptors (TCRs) gamma and beta in 95 advanced ovarian carcinomas.

RESULTS

Gamma/delta T cells are statistically correlated with a brief disease-free interval (P=0.036). CD3 positive tumour-infiltrating T cells are correlated with a brief disease-free interval and with survival (P=0.004 and P=0.0001, respectively). CD3 positive tumour-infiltrating T cells are associated with clinical responsiveness to chemotherapy (P=0.003).

CONCLUSIONS

Further studies are required to better understand the role of gamma/delta T cells in ovarian carcinoma, yet these data underline the importance of host immune response to cancer and the need to better study immune mechanisms to modulate the therapeutic treatment of cancer.