Grammatiki Fotaki

Safe engineering of CAR T cells for adoptive cell therapy of cancer using long‐term episomal gene transfer

Chimeric antigen receptor (CAR) T‐cell therapy is a new successful treatment for refractory B‐cell leukemia. Successful therapeutic outcome depends on long‐term expression of CAR transgene in T cells, which is achieved by delivering transgene using integrating gamma retrovirus (RV) or lentivirus (LV). However, uncontrolled RV/LV integration in host cell genomes has the potential risk of causing insertional mutagenesis. Herein, we describe a novel episomal long‐term cell engineering method using non‐integrating lentiviral (NILV) vector containing a scaffold/matrix attachment region (S/MAR) element, for either expression of transgenes or silencing of target genes. The insertional events of this vector into the genome of host cells are below detection level. CD19 CAR T cells engineered with a NILV‐S/MAR vector have similar levels of CAR expression as T cells engineered with an integrating LV vector, even after numerous rounds of cell division. NILV‐S/MAR‐engineered CD19 CAR T cells exhibited similar cytotoxic capacity upon CD19+ target cell recognition as LV‐engineered T cells and are as effective in controlling tumor growth in vivo. We propose that NILV‐S/MAR vectors are superior to current options as they enable long‐term transgene expression without the risk of insertional mutagenesis and genotoxicity.

Cancer vaccine based on a combination of an infection-enhanced adenoviral vector and pro-inflammatory allogeneic DCs leads to sustained antigen-specific immune responses in three melanoma models

ABSTRACT Autologous patient-derived dendritic cells (DCs) modified ex vivo to present tumor-associated antigens (TAAs) are frequently used as cancer vaccines. However, apart from the stringent logistics in producing DCs on a patient basis, accumulating evidence indicate that ex vivo engineered DCs are poor in migration and in fact do not directly present TAA epitopes to naïve T cells in vivo. Instead, it is proposed that bystander host DCs take up material from vaccine-DCs, migrate and subsequently initiate antitumor T-cell responses. We used mouse models to examine the possibility of using pro-inflammatory allogeneic DCs (alloDCs) to activate host DCs and enable them to promote antigen-specific T-cell immunity. We found that alloDCs were able to initiate host DC activation and migration to draining lymph node leading to T-cell activation. The pro-inflammatory milieu created by alloDCs also led to recruitment of NK cells and neutrophils at the site of injection. Vaccination with alloDCs combined with Ad5M(gp100), an infection-enhanced adenovirus encoding the human melanoma-associated antigen gp100 resulted in generation of CD8+ T cells with a T-cell receptor (TCR) specific for the gp10025-33 epitope (gp100-TCR+). Ad5M(gp100)-alloDC vaccination in combination with transfer of gp100-specific pmel-1 T cells resulted in prolonged survival of B16-F10 melanoma-bearing mice and altered the composition of the tumor microenvironment (TME). We hereby propose that alloDCs together with TAA- or neoepitope-encoding Ad5M can become an “off-the-shelf” cancer vaccine, which can reverse the TME-induced immunosuppression and induce host cellular anti-tumor immune responses in patients without the need of a time-consuming preparation step of autologous DCs.

Pro-inflammatory allogeneic DCs promote activation of bystander immune cells and thereby license antigen-specific T-cell responses

ABSTRACT Accumulating evidence support an important role for endogenous bystander dendritic cells (DCs) in the efficiency of autologous patient-derived DC-vaccines, as bystander DCs take up material from vaccine-DCs, migrate to draining lymph node and initiate antitumor T-cell responses. We examined the possibility of using allogeneic DCs as vaccine-DCs to activate bystander immune cells and promote antigen-specific T-cell responses. We demonstrate that human DCs matured with polyI:C, R848 and IFN-γ (denoted COMBIG) in combination with an infection-enhanced adenovirus vector (denoted Ad5M) exhibit a pro-inflammatory state. COMBIG/Ad5M-matured allogeneic DCs (alloDCs) efficiently activated T-cells and NK-cells in allogeneic co-culture experiments. The secretion of immunostimulatory factors during the co-culture promoted the maturation of bystander-DCs, which efficiently cross-presented a model-antigen to activate antigen-specific CD8+ T-cells in vitro. We propose that alloDCs, in combination with Ad5M as loading vehicle, may be a cost-effective and logistically simplified DC vaccination strategy to induce anti-tumor immune responses in cancer patients.

Abstract A171: Long-term episomal gene transfer for safe engineering of T cells for adoptive cell therapy of cancer

Long-term episomal gene transfer for safe engineering of T-cells for adoptive cell therapy of cancer

Abstract A172: Allogeneic dendritic cells (AlloDCs) transduced with an infection-enhanced adenovirus as adjuvant for cancer immunotherapy

AlloDC cancer immunotherapy utilizes the allogeneic reaction as an immunostimulatory adjuvant. Intratumoral alloDC vaccination reverses the immune suppressed tumor micro-environment and activates anti-tumor immune responses. Herein, we aim to examine the use of Ad5f35PTD, an infection-enhanced serotype 5 adenovirus containing fibers from serotype 35 and cell-penetrating peptides on the hexons, as a vector to deliver tumor-associated antigens to monocyte-derived immature DCs in combination with an established DC maturation cocktail. Ad5f35PTD-transduced, cocktail-matured DCs expressed co-stimulatory and activation molecules and secreted the Th-1 type cytokine IL-12, in vitro . Natural killer (NK) cells migrated better towards medium from Ad5f35PTD-transduced, cocktail-matured DCs than medium from only cocktail-matured DCs, which was in accordance with a higher CXCL-10 chemokine level. The alloDC effect was examined in vivo using mature murine DCs of BALB/c origin (D2SC/I), transduced with Ad5f35PTD encoding the melanoma-associated antigen gp100, injected subcutaneously into C57BL/6 mice. They induced a higher migration of host DCs in the draining lymph node, in comparison to the D2SC/I cells alone. The migrated host DCs efficiently presented the captured gp100 and activated gp100-specific CD8 + T-cells. Moreover, alloDCs transduced with the gp100-encoding Ad5f35PTD reduced the immunosuppressive environment when injected intratumoraly by reducing the ratio of monocytic to granulocytic myeloid-derived suppressor cell compartment and delay tumor growth in a B16 melanoma model, in comparison with the D2SC/I cells alone. Concluding, the Ad5f35PTD transduced alloDCs expressing gp100 showed potency in eliciting tumor-specific immune responses in comparison to the alloDCs alone. Citation Format: Grammatiki Fotaki, Chuan Jin, Alex Karlsson-Parra, Di Yu, Magnus Essand. Allogeneic dendritic cells (AlloDCs) transduced with an infection-enhanced adenovirus as adjuvant for cancer immunotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A172.

Abstract 2311: Adenovirus-transduced allogeneic dendritic cells for cancer immunotherapy

Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA Immunotherapy is currently being established as standard treatment for cancer. Immune checkpoint blockade antibodies can cure a large proportion of patients with refractory melanoma and lung cancer, and adoptive transfer of patient-derived CD19 chimeric antigen receptor (CAR) T cells results in complete remission in a majority of patient with refractory leukemia. Cancer vaccines based on patient-derived dendritic cells (DC) modified ex vivo to present tumor antigens are promising for cancer treatment especially when combined with immune checkpoint blockade antibodies. Ex vivo-modified DCs are however poor in migrating to secondary lymphoid organs after re-administration. In reality, it is more likely endogenous DC that endocytos the injected DC, mature and then migrate to lymph nodes where they present peptide fragments of tumor antigen to T cells together with required co-stimulation. Herein, we present a new strategy utilizing adenovirus (Ad)-transduced allogeneic DCs (alloDCs) as immunostimulatory adjuvant to induce both innate and adaptive immune response. Ad/alloDC can be prepared, tested and made ready for release in advance and quickly be prepared for injection in cancer patients upon request, thereby minimizing GMP-processing and handling of cells. Besides encoding tumor antigens, adenovirus also provides stimulatory danger signals for DC activation. We show that Ad/alloDCs secret a panel of proinflammatory cytokines and chemokines including IL-12 and CXCL10 at high levels in a sustainable fashion. We also show that Ad/alloDC recruit and activate neutrophils and NKs to the site of injection. Ad/alloDC can also recruit and interact with allo-reactive T cells to create a proinflammatory milieu, which further recruit and activate endogenous DCs. We verified that endogenous DCs activated in situ by an Ad/alloDC injection migrate to draining lymph node, where they present the engulfed tumor antigen to T cells. We show that these migratory endogenous DCs facilitate T cell activation and proliferation. Moreover, when injected intratumorally, Ad/alloDCs modulate the immunosuppressive environment by reducing the ratio of monocytic to granulocytic myeloid-derived suppressor cells (MDSC). To evaluate the therapeutic efficacy, we use B16 melanoma tumor-bearing C57Bl/6 mice injected with adenovirus-transduced DCs from Balb/c origin to obtain an allogeneic reaction. We show that Ad/alloDC treatment could significantly delay tumor growth and prolong survival of tumor-bearing mice. Citation Format: Magnus Essand, Grammatiki Fotaki, Chuan Jin, Mohanraj Ramachandran, Jing Ma, Alex Karlsson-Parra, Di Yu. Adenovirus-transduced allogeneic dendritic cells for cancer immunotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2311.

Abstract 996: Metastasis and tumor recurrence from rare SOX9-positive cells in Group 4 medulloblastoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Tumor recurrence is the main cause of death in children with medulloblastoma (MB). MYCN is a marker for poor prognosis which is amplified in SHH and Group 4 but rarely in WNT and Group 3 subgroups of MB. The exact mechanisms for MB relapse are not known but recent findings (Ramaswamy et al. Lancet Oncol., 2013) suggest temporal differences within the four MB subgroups. For instance, SHH tumors recur locally while SHH-independent Group 4 tumors develop distant metastases. In order to study these processes further, we used a previously described transgenic mouse model of MYCN-driven SHH-independent MB (GTML mouse) to recreate the metastatic recurrence of such brain tumors in vivo. We previously showed that the expression of SOX9 transcription factor correlates well with SHH tumors and that only a few scattered SOX9-positive cells are found in SHH-independent GTML tumors similarly to Group 4 human MB. By using a combination of Tet-ON and Tet-OFF inducible systems we managed to target this rare population of SOX9-positive GTML tumor cells in vivo. These cells were able to form a distant recurrence after the tumor bulk in the mice was removed by using dox-inducible oncogene depletion. These relapses showed similar morphology and immunoreactivity of defined MB markers but presented generally higher levels of SOX9 compared to the primary GTML tumors. Additionally, we overexpressed SOX9 in cerebellar stem cells transfected with a mutationally stabilized MYCNT58A and injected them back into the cerebellum of adult mice. Surprisingly, the MB-like tumors that formed migrated and developed in the forebrain in contrast to the cerebellar tumors induced by the same cells transfected with MYCNT58A only. These findings suggest that increased levels of SOX9 drives migration of MYCN-driven MB cells. A similar correlation was found in Group 4 MB patients where isolated metastases had consistently higher SOX9 levels as compared to the corresponding primary tumor. Significance: We have developed a new mouse model for MB recurrence. We show how a rare population of SOX9-positive cells in SHH-independent MB is capable of initiating recurrence after primary tumor removal. The relapsed MB has similar characteristics to the initial tumor but develops at a distant site in the brain, in line with recent data from human tumors. Further characterization of cells with such properties will help to improve our understanding of the mechanisms behind metastatic MB recurrence and to develop treatments against those migrating cell populations. Citation Format: Vasil Savov, Grammatiki Fotaki, Marc Remke, Adrian M. Dubuc, Vijay Ramaswamy, Matko Cancer, Holger Weishaupt, Michael D. Taylor, Fredrik J. Swartling. Metastasis and tumor recurrence from rare SOX9-positive cells in Group 4 medulloblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 996. doi:10.1158/1538-7445.AM2014-996