Translational mini-review series on vaccines: Dendritic cell-based vaccines in renal cancer

Dendritic cells loaded with exosomes derived from cancer stem cell-enriched spheroids as a potential immunotherapeutic option

Cancer stem cells (CSCs) are responsible for therapeutic resistance and recurrence in colorectal cancer. Despite advances in immunotherapy, the inability to specifically eradicate CSCs has led to treatment failure. Hence, identification of appropriate antigen sources is a major challenge in designing dendritic cell (DC)‐based therapeutic strategies against CSCs. Here, in an in vitro model using the HT‐29 colon cancer cell line, we explored the efficacy of DCs loaded with exosomes derived from CSC‐enriched colonospheres (CSC_enr‐EXOs) as an antigen source in activating CSC‐specific T‐cell responses. HT‐29 lysate, HT‐29‐EXOs and CSC_enr lysate were independently assessed as separate antigen sources. Having confirmed CSCs enrichment in spheroids, CSC_enr‐EXOs were purified and characterized, and their impact on DC maturation was investigated. Finally, the impact of the antigen‐pulsed DCs on the proliferation rate and also spheroid destructive capacity of autologous T cells was assessed. CSC_enr‐EXOs similar to other antigen groups had no suppressive/negative impacts on phenotypic maturation of DCs as judged by the expression level of costimulatory molecules. Notably, similar to CSC_enr lysate, CSC_enr‐EXOs significantly increased the IL‐12/IL‐10 ratio in supernatants of mature DCs. CSC_enr‐EXO‐loaded DCs effectively promoted T‐cell proliferation. Importantly, T cells stimulated with CSC_enr‐EXOs disrupted spheroids' structure. Thus, CSC_enr‐EXOs present a novel and promising antigen source that in combination with conventional tumour bulk‐derived antigens should be further explored in pre‐clinical immunotherapeutic settings for the efficacy in hampering recurrence and metastatic spread.

TGFβ in T cell biology and tumor immunity: Angel or devil?

The evolutionally conserved transforming growth factor β (TGFβ) affects multiple cell types in the immune system by either stimulating or inhibiting their differentiation and function. Studies using transgenic mice with ablation of TGFβ or its receptor have revealed the biological significance of TGFβ signaling in the control of T cells. However, it is now clear that TGFβ is more than an immunosuppressive cytokine. Disruption of TGFβ signaling pathway also leads to impaired generation of certain T cell populations. Therefore, in the normal physiological state, TGFβ actively maintains T cell homeostasis and regulates T cell function. However, in the tumor microenvironment, TGFβ creates an immunosuppressive milieu that inhibits antitumor immunity. Here, we review recent advances in our understanding of the roles of TGFβ in the regulation of T cells and tumor immunity.

Adoptive cellular immunotherapy in metastatic renal cell carcinoma: a systematic review and meta-analysis

Purpose

Metastatic renal cell carcinoma (mRCC), as one of the most immunogenic tumors has been the focus of adoptive cellular immunotherapy (ACI), but the effects of ACI on objective response and survival in patients with mRCC are still controversial. Therefore, a systematic review and meta-analysis was performed to address this issue.

Methods

A search was conducted in the PubMed database for randomized clinical trials (RCTs) with ACI in mRCC. All included articles in this study were assessed according to the selection criteria and were divided into two groups: ACI versus no ACI. Outcomes were toxicity, objective response, 1-, 3- and 5-year survival. Risk ratio (RR) and 95% confidence intervals (CI) were calculated using a fixed-effects meta-analysis. Heterogeneity was measured by value of I² or P.

Results

4 studies (469 patients) were included. Most of ACI-related adverse reactions were grade 1 or 2 and reversible. ACI provided significant benefit in terms of objective response (RR = 1.65; 95% CI, 1.15 to 2.38; P = 0.007, I² = 49%), 1-year survival (RR = 1.30; 95% CI, 1.12 to 1.52; P = 0.0008, I² = 0%), 3-year survival (RR = 2.76; 95% CI, 1.85 to 4.14; P<0.00001, I² = 46%) and 5-year survival (RR = 2.42; 95% CI, 1.21 to 4.83; P = 0.01, I² = 28%).

Conclusions

ACI may be a safe and effective treatment for improving objective response, 1-, 3- and 5-year survival in patients with mRCC. Besides, five obstacles for ACI, including high degree of personalization, unsuitable WHO/RECIST response criteria, inadequate identification of tumor-associated antigens (TAAs), lack of effective combination treatments and less attention paid to the quality of ACI products, should be overcome during the successful development of more potent ACI for cancer in the future.

Allogeneic partially HLA-matched dendritic cells pulsed with autologous tumor cell lysate as a vaccine in metastatic renal cell cancer: a clinical phase I/II study

Multi-kinase inhibitors have been established for the treatment of advanced renal cell cancer, but long-term results are still disappointing and immunotherapeutic approaches remain an interesting experimental option particularly in patients with a low tumor burden. DC are crucial for antigen-specific MHC-restricted T cell immunity. Furthermore, allogeneic HLA-molecules pose a strong immunogenic signal and may help to induce tumor-specific T cell responses. In this phase I/II trial, 7 patients with histologically confirmed progressive metastatic RCC were immunized repetitively with 1 × 10 (7) allogeneic partially HLA-matched DC pulsed with autologous tumor lysate following a schedule of 8 vaccinations over 20 weeks. Patients also received 3 Mio IE IL-2 s.c. once daily starting in week 4. Primary endpoints of the study were feasibility and safety. Secondary endpoints were immunological and clinical responses. Vaccination was feasible and safe with no severe toxicity being observed. No objective response could be documented. However, while all patients had documented progress at study entry, 29% of the patients showed SD throughout the study with a mean TTP of 24.6 weeks (range 5 to 96 weeks). In 3/7 patients, TH1-polarized immune responses against RCC-associated antigens were observed. In one patient showing a minimal clinical response and a TTP of 96 weeks, clonally proliferated T cells against yet undefined antigens were induced by the vaccine. Vaccination with tumor antigen loaded DC remains an interesting experimental approach, but should rather be applied in the situation of minimal residual disease after systemic therapy. Additional depletion of regulatory cells might be a promising strategy.

Vaccination therapy in renal cell carcinoma: current position and future options in metastatic and localized disease

As renal cell carcinoma represents one of the most immune-responsive cancers, immunotherapy exhibits a suitable treatment basis. Beside nonspecific stimulation via cytokines, passive specific and active immunotherapy are also appropriate options to recognize and destroy tumor cells. For more than 30 years, research regarding vaccination therapy has been of special interest for the treatment of renal cell carcinoma. However, apart from occasional promising results in Phase I and II trials, vaccination therapy is still considered experimental in this tumor entity, especially owing to missing results from Phase III trials demonstrating clinical efficacy. In the present article, we review data from completed clinical trials of vaccination therapy and also discuss scheduled future trials, in order to assess the current position and possible future fields of application of vaccination therapy in renal cell carcinoma in the era of recently developed targeted therapies.

Chemokine-mediated distribution of dendritic cell subsets in renal cell carcinoma

Background

Renal cell carcinoma (RCC) represents one of the most immunoresponsive cancers. Antigen-specific vaccination with dendritic cells (DCs) in patients with metastatic RCC has been shown to induce cytotoxic T-cell responses associated with objective clinical responses. Thus, clinical trials utilizing DCs for immunotherapy of advanced RCCs appear to be promising; however, detailed analyses concerning the distribution and function of DC subsets in RCCs are lacking.

Methods

We characterized the distribution of the different immature and mature myeloid DC subsets in RCC tumour tissue and the corresponding normal kidney tissues. In further analyses, the expression of various chemokines and chemokine receptors controlling the migration of DC subsets was investigated.

Results

The highest numbers of immature CD1a+ DCs were found within RCC tumour tissue. In contrast, the accumulation of mature CD83+/DC-LAMP+ DCs were restricted to the invasive margin of the RCCs. The mature DCs formed clusters with proliferating T-cells. Furthermore, a close association was observed between MIP-3α-producing tumour cells and immature CCR6+ DC recruitment to the tumour bed. Conversely, MIP-3β and SLC expression was only detected at the tumour border, where CCR7-expressing T-cells and mature DCs formed clusters.

Conclusion

Increased numbers of immature DCs were observed within the tumour tissue of RCCs, whereas mature DCs were found in increased numbers at the tumour margin. Our results strongly implicate that the distribution of DC subsets is controlled by local lymphoid chemokine expression. Thus, increased expression of MIP-3α favours recruitment of immature DCs to the tumour bed, whereas de novo local expression of SLC and MIP-3β induces accumulation of mature DCs at the tumour margin forming clusters with proliferating T-cells reflecting a local anti-tumour immune response.

Indoleamine-2,3-dioxygenase enzyme expression and activity in polarized dendritic cells

BACKGROUND AIMS

Polarized mature dendritic cells (DC) can activate cytolytic T-lymphocyte (CTL) responses and may be a more effective clinical strategy in DC-based cancer vaccines. A subset of mature DC can down-regulate the T-cell immune response through expression of indoleamine-2,3-dioxygenase (IDO). We determined whether polarizing DC ex vivo increased IDO expression and activity.

METHODS

Peripheral blood monocytes from healthy volunteers were cultured ex vivo in polarizing and non-polarizing culture conditions. DC IDO expression was detected by Western blot. IDO enzyme activity was determined by high-performance liquid chromatography (HPLC) measurement of kynurenine (K) and tryptophan (T) concentrations in culture supernatants.

RESULTS

IDO protein was markedly increased in DC after polarization (median 1222.4%, range 331.5-2113.3%) versus non-polarized DC (median 28.3%, range 3.7-119.8%; P=0.04). The median K/T ratio was significantly higher in polarized DC versus non-polarized DC (6.34, range 6.02-6.65, versus 0.047, range 0.004-0.541; P=0.04). IDO protein expression correlated with enzyme activity (r=0.80, P=0.002).

CONCLUSIONS

DC polarizing culture conditions increased expression of IDO protein and IDO enzyme activity. DC culture and maturation methodologies may impact the effectiveness of adoptive DC therapy.

Sunitinib reverses type-1 immune suppression and decreases T-regulatory cells in renal cell carcinoma patients

PURPOSE

Immune dysfunction is well documented in renal cell carcinoma (RCC) patients and likely contributes to tumor evasion. This dysfunction includes a shift from a type-1 to a type-2 T-cell cytokine response and enhanced T-regulatory (Treg) cell expression. Given the antitumor activity of select tyrosine kinase inhibitors such as sunitinib in metastatic RCC (mRCC) patients, it is relevant to assess their effect on the immune system.

EXPERIMENTAL DESIGN

Type-1 (IFNgamma) and type-2 (interleukin-4) responses were assessed in T cells at baseline and day 28 of treatment with sunitinib (50 mg/d) by measuring intracellular cytokines after in vitro stimulation with anti-CD3/anti-CD28 antibodies.

RESULTS

After one cycle of treatment, there was a significant increase in the percentage of IFNgamma-producing T cells (CD3(+), P < 0.001; CD3(+)CD4(+), P = 0.001), a reduction in interleukin-4 production (CD3(+) cells, P = 0.05), and a diminished type-2 bias (P = 0.005). The increase in type-1 response may be partly related to modulation of Treg cells. The increased percentage of Treg cells noted in mRCC patients over healthy donors (P = 0.001) was reduced after treatment, although not reaching statistical significance. There was, however, an inverse correlation between the increase in type-1 response after two cycles of treatment and a decrease in the percentage of Treg cells (r = -0.64, P = 0.01). In vitro studies suggest that the effects of sunitinib on Treg cells are indirect.

CONCLUSIONS

The demonstration that sunitinib improved type-1 T-cell cytokine response in mRCC patients while reducing Treg function provides a basis for the rational combination of sunitinib and immunotherapy in mRCC.

Interferon-alpha (IFN-alpha)-conditioned DC preferentially stimulate type-1 and limit Treg-type in vitro T-cell responses from RCC patients

Dendritic cells (DCs) are potent antigen presenting cells and represent attractive candidates for use in novel immunotherapies for patients with renal cell carcinoma (RCC), a disease that has proven refractory to conventional treatment modalities, such as chemotherapy and radiotherapy. Given the perceived need to augment antitumor type-1 immunity (TC1 and Th1) as a therapeutic end point, and the known functional plasticity of DC populations that may display heterogeneous capacity to promote T-cell responses, we sought to identify a preferred DC preparation with this capacity. We compared 2 different preparations of monocyte-derived DC using interferon-alpha (IFN-alpha) (IFN-DC and alphaDC1) with classic DCs "matured" (mDCs) using interleukin-1beta/interleukin-6/tumor necrosis factor-alpha/prostaglandin E2, for their ability to promote autologous TC1 antitumor responses from RCC patients in vitro. IFN-alpha-conditioned DC promoted significantly higher numbers of RCC-specific CD8+ T cells exhibiting a cytotoxic phenotype after in vitro stimulation (IVS) than cytokine cocktail-mDCs. Furthermore, IVS using IFN-DCs was able to diminish regulatory-type T cells among CD4+ T-cell responder populations versus IVS using conventional mDC-based vaccines. These data emphasize an important role for IFN-alpha in modulating the immunologic functions of DCs toward a polarized DC1-type capable of coordinately promoting TH1-type and TC1-type T-cell mediated immunity and supports the translational development of patient-derived IFN-alpha-conditioned DC for use in novel immunotherapies for patients with RCC, and in whom, endogenous tumor-specific TC1 effector cells may be dysfunctional, anergic, or prone to undergo apoptosis.