Favorable Tumor Microenvironment Research Articles

Abstract CT099: A phase I study of intralesional Bacillus Calmette-Guerin (BCG) followed by ipilimumab therapy in patients with advanced metastatic melanoma

Abstract Background: Immunotherapies with checkpoint inhibitors have revolutionized the treatment of advanced melanomas. Nonetheless, a subset of patients fail to benefit clinically from these immunotherapeutics, and thus strategies aimed at inducing a favorable inflammatory tumor microenvironment prior to immunotherapy are currently being investigated by means of combination therapies. Bacillus Calmette-Guerin (BCG) is a living attenuated strain of Mycobacterium bovis that stimulates cell-mediated immunity by producing a localized and self-limiting infection. This immunostimulatory agent has shown evidence of anti-tumor activity in several clinical studies with suggested induction of non-specific immune responses, thereby warranting further investigation in a combination therapy setting. Methods: This phase I study aimed to determine the safety, clinical efficacy and immunogenicity of the administration of intralesional BCG followed by up to four intravenous infusions of ipilimumab (anti-CTLA4) (NCT01838200). Patients with histologically confirmed stage III/IV metastatic melanoma with at least one injectable lesion, and no prior immunotherapy or autoimmune disease were recruited for this study. Patients received up to four 3 mg/kg ipilimumab infusions every 3 weeks from 36 days after intralesion BCG injection containing 0.16 - 0.64 x 106 colony-forming units. Serum samples were collected prior to each therapeutic intervention as a means of investigating immunogenicity. Humoral immune responses were investigated using the Immunome protein array, a high-content array with 1627 full-length, correctly folded, and fully functional immobilized proteins that enables the interrogation of the depth and breadth of the immune response. Results: 5 patients were enrolled in this study, with 2 displaying high grade immune-related adverse events (irAEs) (grade 3 hepatitis and grade 4 colitis), which led to the early discontinuation of this trial. These irAEs were in accordance with ipilimumab-related reported toxicities. Furthermore, all patients displayed evidence of clinically progressive disease, with no evident therapeutic benefit. Patients displaying irAEs were characterized by drastic increases in their antibody repertoire towards tumor and self-antigens, when compared to those with no reported irAEs (42% vs. 3% of array content, respectively). This high order of de novo and induced antibodies was detected in time points preceding clinical detection of these high-grade toxicities. However, these antibody profiles did not overlap between patients, with unique antigen targets detected in each patient, suggesting evidence of a systemic B-cell deregulation, rather than an induced specific anti-tumor response. Conclusions: Intralesional BCG followed by ipilimumab therapy was not well tolerated in advanced melanoma patients, and showed no evidence of clinical benefit. Investigating humoral immunity may offer a means to detect the early onset of irAEs in an immunotherapeutic clinical trial setting. Citation Format: Jessica Duarte, Katherine Woods, Andreas Behren, Jonathan Cebon. A phase I study of intralesional Bacillus Calmette-Guerin (BCG) followed by ipilimumab therapy in patients with advanced metastatic melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT099. doi:10.1158/1538-7445.AM2017-CT099

Neoadjuvant chemoradiotherapy of pancreatic cancer induces a favorable immunogenic tumor microenvironment associated with increased major histocompatibility complex class I-related chain A/B expression.

Damage-associated molecular patterns (DAMPs) are related to immune responses in malignant tumors including tumor-infiltrating lymphocytes (TILs). The aim of the present study was to determine the relationship between expression of components of DAMPs and TILs in pancreatic cancer patients who underwent neoadjuvant chemoradiotherapy (NACRT) versus those who did not. NACRT was administered to 51 patients with borderline-resectable pancreatic cancer and not to 33 patients with resectable pancreatic cancer. Resected specimens were analyzed for the presence of DAMPs, major histocompatibility complex class I-related chain A/B (MICA/B), and CD8+ TILs, CD4+ TILs, and forkhead box P3 positive (Foxp3+ ) TILs. The Treg/TIL ratio was obtained by dividing the number of Foxp3+ TILs, a surrogate for regulatory T cells, by the sum of CD8+ and CD4+ TILs. Overexpression of calreticulin, Hsp70, and MICA/B were all significantly correlated with NACRT administration. In the NACRT group, high MICA/B expression was associated with a low Treg/TIL ratio, indicating a favorable immunogenic tumor microenvironment. Patients with a lower Treg/TIL ratio had longer survival. Overexpression of MICA/B, a component of DAMPs induced by NACRT, may play an important role in acquiring a favorable immune response for pancreatic cancer which contributes to longer survival, suggesting the potential of immunotherapy of this recalcitrant disease, especially for patients with overexpression of DAMPs.

Inhibition of Bone Marrow-Derived Mesenchymal Stem Cells Homing Towards Triple-Negative Breast Cancer Microenvironment Using an Anti-PDGFRβ Aptamer.

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are shown to participate in tumor progression by establishing a favorable tumor microenvironment (TME) that promote metastasis through a cytokine networks. However, the mechanism of homing and recruitment of BM-MSCs into tumors and their potential role in malignant tissue progression is poorly understood and controversial. Here we show that BM-MSCs increase aggressiveness of triple-negative breast cancer (TNBC) cell lines evaluated as capability to migrate, invade and acquire stemness markers. Importantly, we demonstrate that the treatment of BM-MSCs with a nuclease-resistant RNA aptamer against platelet-derived growth factor receptor β (PDGFRβ) causes the inhibition of receptor-dependent signaling pathways thus drastically hampering BM-MSC recruitment towards TNBC cell lines and BM-MSCs trans-differentiation into carcinoma-associated fibroblast (CAF)-like cells. Moreover, in vivo molecular imaging analysis demonstrated the aptamer ability to prevent BM-MSCs homing to TNBC xenografts. Collectively, our results indicate the anti-PDGFRβ aptamer as a novel therapeutic tool to interfere with BM-MSCs attraction to TNBC providing the rationale to further explore the aptamer in more complex pre-clinical settings.

Normalization of Tumor Vessels by Tie2 Activation and Ang2 Inhibition Enhances Drug Delivery and Produces a Favorable Tumor Microenvironment

A destabilized tumor vasculature leads to limited drug delivery, hypoxia, detrimental tumor microenvironment, and even metastasis. We performed a side-by-side comparison of ABTAA (Ang2-Binding and Tie2-Activating Antibody) and ABA (Ang2-Blocking Antibody) in mice with orthotopically implanted glioma, with subcutaneously implanted Lewis lung carcinoma, and with spontaneous mammary cancer. We found that Tie2 activation induced tumor vascular normalization, leading to enhanced blood perfusion and chemotherapeutic drug delivery, markedly lessened lactate acidosis, and reduced tumor growth and metastasis. Moreover, ABTAA favorably altered the immune cell profile within tumors. Together, our findings establish that simultaneous Tie2 activation and Ang2 inhibition form a powerful therapeutic strategy to elicit a favorable tumor microenvironment and enhanced delivery of a chemotherapeutic agent into tumors.

Abstract IA13: The interplay between tumor cells, cancer associated fibroblasts, and immature myeloid cells in the esophageal tumor microenvironment

Abstract Esophageal cancer has two major subtypes: esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). ESCC is more common worldwide and illustrative of other SCCs (e.g. head/neck, lung) from a molecular pathogenesis viewpoint. EAC is rising in incidence in the United States and Western Europe. Unfortunately, 5-year survival remains dismal for both types, at about 15%. Interrogation of the esophageal tumor microenvironment, replete with desmoplasia, CAFs and diverse immune cells, may afford opportunities to reveal new therapeutic targets, especially in a combinatorial fashion. We have generated previously a conditional knockout model of p120-catenin whereby mice develop preneoplastic and neoplastic lesions in the esophagus. Tumor-derived cells secrete granulocyte macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor-α (TNFα). The tumors contain significant desmoplasia and immune cell infiltration. Immature myeloid cells (myeloid deriver suppressor cells or MDSCs) comprise a significant percentage of the immune cells present and likely participate in fostering a favorable tumor microenvironment, including the activation of fibroblasts. We have identified CD38 as playing a vital role in MDSC biology. CD38 belongs to the ADP-ribosyl cyclase family and possesses both ectoenzyme and receptor functions. It has been described to function in lymphoid and early myeloid cell differentiation, cell activation, and neutrophil chemotaxis. CD38high MDSCs are more immature than MDSCs lacking CD38 expression, suggesting a potential role for CD38 in the maturation halt found in MDSC populations. CD38high MDSCs also possess a greater capacity to suppress activated T cells, and promote tumor growth to a greater degree than CD38low MDSCs, likely as a result of increased iNOS production. In addition, we have identified novel tumor–derived factors, specifically IL-6, IGFBP3, and CXCL16, which induce CD38 expression by MDSCs ex vivo. Finally, we have detected an expansion of CD38+ MDSCs in peripheral blood of advanced-stage cancer patients. Additional work reveals cross-talk between CAFs and tumor cells through the induction of IL-6 and RANTES, suggesting there is interaction between tumor cells, CAFs and MDSCs. In aggregate, we find that CD38 (on MDSCs), IL-6 and RANTES (secreted by tumor cells and CAFs) serve to provide novel approaches in therapy. Citation Format: Tatiana Karakasheva, Eric Lin, Phil Hicks, Todd Waldron, Anil K. Rustgi. The interplay between tumor cells, cancer associated fibroblasts, and immature myeloid cells in the esophageal tumor microenvironment. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr IA13.

Regulation of prostate cancer progression by the tumor microenvironment

Prostate cancer remains the most frequently diagnosed cancer in men in North America, and despite recent advances in treatment patients with metastatic disease continue to have poor five-year survival rates. Recent studies in prostate cancer have revealed the critical role of the tumor microenvironment in the initiation and progression to advanced disease. Experimental data have uncovered a reciprocal relationship between the cells in the microenvironment and malignant tumor cells in which early changes in normal tissue microenvironment can promote tumorigenesis and in turn tumor cells can promote further pro-tumor changes in the microenvironment. In the tumor microenvironment, the presence of persistent immune infiltrates contributes to the recruitment and reprogramming of other non-immune stromal cells including cancer-associated fibroblasts and a unique recently identified population of metastasis-initiating cells (MICs). These MICs, which can also be found as part of the circulating tumor cell (CTC) population in PC patients, promote cancer cell transformation, enhance metastatic potential and confer therapeutic resistance. MICs act can on other cells within the tumor microenvironment in part by secreting exosomes that reprogram adjacent stromal cells to create a more favorable tumor microenvironment to support continued cancer growth and progression. We review here the current data on the intricate relationship between inflammation, reactive stroma, tumor cells and disease progression in prostate cancer.

Oncogenic CARMA1 couples NF-κB and β-catenin signaling in diffuse large B-cell lymphomas.

Constitutive activation of the antiapoptotic nuclear factor-κB (NF-κB) signaling pathway is a hallmark of the activated B-cell-like (ABC) subtype of diffuse large B-cell lymphomas (DLBCL). Recurrent oncogenic mutations are found in the scaffold protein CARMA1 (CARD11) that connects B-cell receptor (BCR) signaling to the canonical NF-κB pathway. We asked how far additional downstream processes are activated and contribute to the oncogenic potential of DLBCL-derived CARMA1 mutants. To this end, we expressed oncogenic CARMA1 in the NF-κB negative DLBCL lymphoma cell line BJAB. By a proteomic approach we identified recruitment of β-catenin and its destruction complex consisting of APC, AXIN1, CK1α and GSK3β to oncogenic CARMA1. Recruitment of the β-catenin destruction complex was independent of CARMA1-BCL10-MALT1 complex formation or constitutive NF-κB activation and promoted the stabilization of β-catenin. The β-catenin destruction complex was also recruited to CARMA1 in ABC DLBCL cell lines, which coincided with elevated β-catenin expression. In line, β-catenin was frequently detected in non-GCB DLBCL biopsies that rely on chronic BCR signaling. Increased β-catenin amounts alone were not sufficient to induce classical WNT target gene signatures, but could augment TCF/LEF-dependent transcriptional activation in response to WNT signaling. In conjunction with NF-κB, β-catenin enhanced expression of immunosuppressive interleukin-10 and suppressed antitumoral CCL3, indicating that β-catenin can induce a favorable tumor microenvironment. Thus, parallel activation of NF-κB and β-catenin signaling by gain-of-function mutations in CARMA1 augments WNT stimulation and is required for regulating the expression of distinct NF-κB target genes to trigger cell-intrinsic and extrinsic processes that promote DLBCL lymphomagenesis.

H3K27 Demethylase JMJD3 Employs the NF-κB and BMP Signaling Pathways to Modulate the Tumor Microenvironment and Promote Melanoma Progression and Metastasis.

Histone methylation is a key epigenetic mark that regulates gene expression. Recently, aberrant histone methylation patterns caused by deregulated histone demethylases have been associated with carcinogenesis. However, the role of histone demethylases, particularly the histone H3 lysine 27 (H3K27) demethylase JMJD3, remains largely uncharacterized in melanoma. Here, we used human melanoma cell lines and a mouse xenograft model to demonstrate a requirement for JMJD3 in melanoma growth and metastasis. Notably, in contrast with previous reports examining T-cell acute lymphoblastic leukemia and hepatoma cells, JMJD3 did not alter the general proliferation rate of melanoma cells in vitro. However, JMJD3 conferred melanoma cells with several malignant features such as enhanced clonogenicity, self-renewal, and transendothelial migration. In addition, JMJD3 enabled melanoma cells not only to create a favorable tumor microenvironment by promoting angiogenesis and macrophage recruitment, but also to activate protumorigenic PI3K signaling upon interaction with stromal components. Mechanistic investigations demonstrated that JMJD3 transcriptionally upregulated several targets of NF-κB and BMP signaling, including stanniocalcin 1 (STC1) and chemokine (C-C motif) ligand 2 (CCL2), which functioned as downstream effectors of JMJD3 in self-renewal and macrophage recruitment, respectively. Furthermore, JMJD3 expression was elevated and positively correlated with that of STC1 and CCL2 in human malignant melanoma. Moreover, we found that BMP4, another JMJD3 target gene, regulated JMJD3 expression via a positive feedback mechanism. Our findings reveal a novel epigenetic mechanism by which JMJD3 promotes melanoma progression and metastasis, and suggest JMJD3 as a potential target for melanoma treatment.

Improving immunological tumor microenvironment using electro-hyperthermia followed by dendritic cell immunotherapy

BackgroundThe treatment of intratumoral dentritic cells (DCs) commonly fails because it cannot evoke immunity in a poor tumor microenvironment (TME). Modulated electro-hyperthermia (mEHT, trade-name: oncothermia) represents a significant technological advancement in the hyperthermia field, allowing the autofocusing of electromagnetic power on a cell membrane to generate massive apoptosis. This approach turns local immunogenic cancer cell death (apoptosis) into a systemic anti-tumor immune response and may be implemented by treatment with intratumoral DCs.MethodsThe CT26 murine colorectal cancer model was used in this investigation. The inhibition of growth of the tumor and the systemic anti-tumor immune response were measured. The tumor was heated to a core temperature of 42 °C for 30 min. The matured synergetic DCs were intratumorally injected 24 h following mEHT was applied.ResultsmEHT induced significant apoptosis and enhanced the release of heat shock protein70 (Hsp70) in CT26 tumors. Treatment with mEHT-DCs significantly inhibited CT26 tumor growth, relative to DCs alone or mEHT alone. The secondary tumor protection effect upon rechallenging was observed in mice that were treated with mEHT-DCs. Immunohistochemical staining of CD45 and F4/80 revealed that mEHT-DC treatment increased the number of leukocytes and macrophages. Most interestingly, mEHT also induced infiltrations of eosinophil, which has recently been reported to be an orchestrator of a specific T cell response. Cytotoxic T cell assay and ELISpot assay revealed a tumor-specific T cell activity.ConclusionsThis study demonstrated that mEHT induces tumor cell apoptosis and enhances the release of Hsp70 from heated tumor cells, unlike conventional hyperthermia. mEHT can create a favorable tumor microenvironment for an immunological chain reaction that improves the success rate of intratumoral DC immunotherapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1690-2) contains supplementary material, which is available to authorized users.

Critical Role of Tumor Microenvironment in Shaping NK Cell Functions: Implication of Hypoxic Stress.

Blurring the boundary between innate and adaptive immune system, natural killer (NK) cells, a key component of the innate immunity, are recognized as potent anticancer mediators. Extensive studies have been detailed on how NK cells get activated and recognize cancer cells. In contrast, few studies have been focused on how tumor microenvironment-mediated immunosubversion and immunoselection of tumor-resistant variants may impair NK cell function. Accumulating evidences indicate that several cell subsets (macrophages, myeloid-derived suppressive cells, T regulatory cells, dendritic cells, cancer-associated fibroblasts, and tumor cells), their secreted factors, as well as metabolic components (i.e., hypoxia) have immunosuppressive roles in the tumor microenvironment and are able to condition NK cells to become anergic. In this review, we will describe how NK cells react with different stromal cells in the tumor microenvironment. This will be followed by a discussion on the role of hypoxic stress in the regulation of NK cell functions. The aim of this review is to provide a better understanding of how the tumor microenvironment impairs NK cell functions, thereby limiting the use of NK cell-based therapy, and we will attempt to suggest more efficient tools to establish a more favorable tumor microenvironment to boost NK cell cytotoxicity and control tumor progression.

Anti-tumor activity of staurosporine in the tumor microenvironment of cervical cancer: An in vitro study.

The fundamental events for cancer progression and metastases include loss of cell adhesion, cell proliferation, anchorage-independent cell growth (evading anoikis), cell migration and cell invasion. All these events leading to cancer progression happen in a favorable nurturing tumor microenvironment. This study was designed to explore the anti-tumor activity of staurosporine (a nonspecific protein kinase inhibitor) in the tumor microenvironment of cervical cancer. The anti-tumor activity of staurosporine was investigated by cell adhesion assay, colony formation assay, apoptosis assay and quantitative real-time polymerase chain reaction (PCR) in cervical cancer cell lines. The cell adhesion assay showed that staurosporine induces adhesion of cervical cancer cells to the extracellular matrix (ECM) protein fibronectin. The soft agar colony formation assay showed that staurosporine inhibits both the number and size of colony formation in a dose dependent manner and also induces adherent tendency in the cancer cells. Staurosporine also induces prominent apoptosis in single cell suspensions compared to adherent cells. Stroma cell induced transcription of matrix metalloprotease 1 (MMP1) and matrix metalloprotease 2 (MMP2) in cervical cancer cells was inhibited by staurosporine. Our results indicate that staurosporine induces anti-tumor response in the cervical tumor microenvironment by inhibiting the fundamental events for cancer progression and metastases. The present study represents an attractive area for further research and opens up new avenues towards the understanding of cervical cancer therapeutics.

Cancer Associated Fibroblasts in Multiple Myeloma: The Urokinase Receptor System in Tumor Growth Regulation

BACKGROUND:The multiple myeloma (MM) represents a process in which an asymptomatic stage of monoclonal gammopathy of undetermined significance (MGUS) precedes virtually all cases of MM. It is known that tumor progression are determined by a favorable tumor microenvironment (TME) and in this scenario fibroblasts represent the principal cellular component in the TME.A particular subpopulation of fibroblasts, cancer associated fibroblasts (CAFs), has recently raised the interest of many researchers due to their active participation in tumor growth and invasion and their association with higher malignancy grade, and poor prognosis. Recent findings indicate that the urokinase plasminogen activator (u-PA), and the urokinase receptor (u-PAR) are critical in cell invasion and degradation processes. Degradation and remodeling of the surrounding tissues are crucial in the early steps of tumor progression by facilitating expansion of the tumor mass, tumor cell proliferation, migration, and invasion. uPAR is expressed by multiple tumor associated cell types found in tumors. Targeting uPAR expressed on tumor-associated cells may be as important as targeting uPAR expressed on tumor cells and may lead to enhanced antitumor activity especially in those tumor types expressing uPAR on both types of cells.METHODS:Cell purification and cultures: BM mononuclear cells (BMMCs) were isolated by Ficoll-Hypaque gradient from heparinized bone marrow (BM) aspirates from 10 patients with relapse/refractory MM, 7 patients with asymptomatic MM, 7 with remission MM, 10 with MGUS. Fibroblasts were purified from BM stromal cells BMSCs through anti-fibroblasts-microbeads, and culture in DMEM medium with 10% FBS.Cell phenotype analysis: CAFs were analyzed on heparinized bone marrow aspirates and they were identified by FSP1 and α-smooth muscle actin (α-SMA) expression on gated CD45-population. Expression of alpha-SMA in BM purified fibroblasts was also demonstrated by immunofluorescence staining.Immunofluorescence: CAFs were cultured in DMEM medium, fixed in paraformaldehyde, and permeabilized according to routine methods. The primary antibodies were anti–uPAR, and anti–α-SMA. Fibroblast nuclei were stained with DAPI.Quantitative PCR analysis: Complementary DNA was prepared from 1 ug total RNA using a GoScript reverse transcription system. The relative quantity of uPA, uPAR, MMP-2, α-SMA and vimentin messenger RNA were measured using the Applied Biosystems 7500 Fast Real-Time PCR System and determined by the comparative Ct method using 18S ribosomal RNA as the normalization gene.The study was approved by the local Ethics Committee and all patients provided their informed consent in accordance with the Declaration of Helsinki.RESULTS:Cell phenotype analysis:Flow cytometry analysis showed that CAFs were increased in patients with relapse-MM compared to patients with asymptomatic, remission MM and MGUS suggesting that CAFs expansion is involved in MM progression.CAFs activation: The increased frequency of alpha-SMA in CAFs of relapsed MM patients was demonstrated by the immunofluorescence analysis. Overall, these results suggest that MM activation is associated with the overexpression of uPAR. (Fig.1)CAFs activation was also demonstrated by Real Time PCR and the figure 2 shows the overexpression of activation molecules as well as proinvasive systems in CAF of relapsed MM in comparison of MGUS and asymptomatic MM.CONCLUSIONS:In MM developement and progression the BM niche appears to play an important role in differentiation, migration, proliferation, and drug resistance of the malignant PCs.The main goal of this proposal was to globally approach the expression of CAFs’ activation and proinvasive systems in the initiation and progression of MM.Our results highlight an important mile stone on the phisiopatology of MM progression demonstrating that the CAF-activated phenotype is associated with an over-expression of the most important pro-invasive systems, and in particular the relapsed-MM CAFs seem to overexpress the fibrinolytic pattern of invasive tumor-like cells. On the basis of these results we aim to develop a biological model which can become a potential therapeutic target. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Loss of Nm23 is associated with a more favorable tumor microenvironment in patients with breast cancer.

Nm23 is a metastasis suppressor gene whose downregulation triggers metastatic progression. The aim of this study was to investigate the expression of Nm23 in breast carcinomas and its relationship with tumor microenvironment markers. A retrospective study was done (128 breast cancer patients from 2007 to 2010). Nm23, LPA1, SMA, CD34, CD8, and CD68 protein expressions were evaluated using immunohistochemistry. Image analysis was used to determine the immunostaining percentage area of Nm23, LPA1, and SMA; the number of the total vessel fraction CD34 positive; and the number of CD8+ and CD68+ cells. The mean ± SE was calculated. The differences among groups were evaluated using Student t-test for parametric data and Mann Whitney U test for nonparametric data. Cases were divided into two groups: Nm23+ and Nm23-. LPA1 immunostaining was significantly increased in Nm23- group. Immunostaining percentage area of SMA was not significantly higher when Nm23 was negative. CD34 immunopositive blood vessels, number of T CD8+ cells, and the number of macrophage CD68+ cells were increased when Nm23 was absent. Our results suggest that the absence of Nm23 causes an increase in LPA1, CD8+ and CD68+ inflammatory cells, and angiogenesis marker. Therefore, Nm23 loss could be associated with a more favorable environment for the development and dissemination of breast cancer. However, more studies are needed to determine this association.

Response to BRAF inhibition in melanoma is enhanced when combined with immune checkpoint blockade.

BRAF-targeted therapy results in objective responses in the majority of patients; however, the responses are short lived (∼6 months). In contrast, treatment with immune checkpoint inhibitors results in a lower response rate, but the responses tend to be more durable. BRAF inhibition results in a more favorable tumor microenvironment in patients, with an increase in CD8(+) T-cell infiltrate and a decrease in immunosuppressive cytokines. There is also increased expression of the immunomodulatory molecule PDL1, which may contribute to the resistance. On the basis of these findings, we hypothesized that BRAF-targeted therapy may synergize with the PD1 pathway blockade to enhance antitumor immunity. To test this hypothesis, we developed a BRAF(V600E)/Pten(-/-) syngeneic tumor graft immunocompetent mouse model in which BRAF inhibition leads to a significant increase in the intratumoral CD8(+) T-cell density and cytokine production, similar to the effects of BRAF inhibition in patients. In this model, CD8(+) T cells were found to play a critical role in the therapeutic effect of BRAF inhibition. Administration of anti-PD1 or anti-PDL1 together with a BRAF inhibitor led to an enhanced response, significantly prolonging survival and slowing tumor growth, as well as significantly increasing the number and activity of tumor-infiltrating lymphocytes. These results demonstrate synergy between combined BRAF-targeted therapy and immune checkpoint blockade. Although clinical trials combining these two strategies are ongoing, important questions still remain unanswered. Further studies using this new melanoma mouse model may provide therapeutic insights, including optimal timing and sequence of therapy.

BRAF Inhibition Is Associated with Enhanced Melanoma Antigen Expression and a More Favorable Tumor Microenvironment in Patients with Metastatic Melanoma

To evaluate the effects of BRAF inhibition on the tumor microenvironment in patients with metastatic melanoma. Thirty-five biopsies were collected from 16 patients with metastatic melanoma pretreatment (day 0) and at 10 to 14 days after initiation of treatment with either BRAF inhibitor alone (vemurafenib) or BRAF + MEK inhibition (dabrafenib + trametinib) and were also taken at time of progression. Biopsies were analyzed for melanoma antigens, T-cell markers, and immunomodulatory cytokines. Treatment with either BRAF inhibitor alone or BRAF + MEK inhibitor was associated with an increased expression of melanoma antigens and an increase in CD8+ T-cell infiltrate. This was also associated with a decrease in immunosuppressive cytokines [interleukin (IL)-6 and IL-8] and an increase in markers of T-cell cytotoxicity. Interestingly, expression of exhaustion markers TIM-3 and PD1 and the immunosuppressive ligand PDL1 was increased on treatment. A decrease in melanoma antigen expression and CD8 T-cell infiltrate was noted at time of progression on BRAF inhibitor alone and was reversed with combined BRAF and MEK inhibition. Together, these data suggest that treatment with BRAF inhibition enhances melanoma antigen expression and facilitates T-cell cytotoxicity and a more favorable tumor microenvironment, providing support for potential synergy of BRAF-targeted therapy and immunotherapy. Interestingly, markers of T-cell exhaustion and the immunosuppressive ligand PDL1 are also increased with BRAF inhibition, further implying that immune checkpoint blockade may be critical in augmenting responses to BRAF-targeted therapy in patients with melanoma.

Anaphylatoxin C5a Creates a Favorable Microenvironment for Lung Cancer Progression

The complement system contributes to various immune and inflammatory diseases, including cancer. In this study, we investigated the capacity of lung cancer cells to activate complement and characterized the consequences of complement activation on tumor progression. We focused our study on the production and role of the anaphylatoxin C5a, a potent immune mediator generated after complement activation. We first measured the capacity of lung cancer cell lines to deposit C5 and release C5a. C5 deposition, after incubation with normal human serum, was higher in lung cancer cell lines than in nonmalignant bronchial epithelial cells. Notably, lung malignant cells produced complement C5a even in the absence of serum. We also found a significant increase of C5a in plasma from patients with non-small cell lung cancer, suggesting that the local production of C5a is followed by its systemic diffusion. The contribution of C5a to lung cancer growth in vivo was evaluated in the Lewis lung cancer model. Syngeneic tumors of 3LL cells grew slower in mice treated with an antagonist of the C5a receptor. C5a did not modify 3LL cell proliferation in vitro but induced endothelial cell chemotaxis and blood-vessels formation. C5a also contributed to the immunosuppressive microenvironment required for tumor growth. In particular, blockade of C5a receptor significantly reduced myeloid-derived suppressor cells and immunomodulators ARG1, CTLA-4, IL-6, IL-10, LAG3, and PDL1 (B7H1). In conclusion, lung cancer cells have the capacity to generate C5a, a molecule that creates a favorable tumor microenvironment for lung cancer progression.

Pre‐existing fas ligand (FasL) in cancer cells elicits tumor‐specific protective immunity, but delayed induction of FasL expression after inoculation facilitates tumor formation

Overexpression of Fas ligand (FasL) in cancer cells elicits potential antitumor effects via recruitment of neutrophils. Conversely, FasL-expressing tumors may counterattack tumor-infiltrating lymphocytes by delivering apoptotic death signals via Fas/FasL interactions, which may lead to tumor escape. In order to distinguish the role of FasL in antitumor activity and tumor progression, Lewis lung carcinoma cells (LLC-1) were used to establish the cell line LLC-FasL, in which FasL expression was repressed by doxycycline (Dox) treatment and induced in the absence of Dox. LLC-FasL cells promote tumor regression when expressing FasL, whereas tumor outgrowth is observed by depletion of FasL expression. To investigate whether initial expression of FasL during tumor formation is critical for FasL-mediated tumor regression, Dox-treated LLC-FasL cells were inoculated into Dox-treated mice, but Dox treatment was stopped 5 days after inoculation. When low cell numbers were inoculated, we observed 80% survival and no tumor formation, whereas no mice survived inoculation with high cell numbers, despite the delayed induction of FasL by Dox withdrawal. The inoculation of a high density of cells may establish a favorable tumor microenvironment before the expression of FasL. Our findings demonstrate that FasL may elicit antitumor activity when it is initially present on injected cancer cells and thus can act prior to tumor microenvironment formation. Furthermore, a well-established tumor microenvironment abrogates FasL-mediated antitumor activity.

Deletion of p120-Catenin Results in a Tumor Microenvironment with Inflammation and Cancer that Establishes It as a Tumor Suppressor Gene

p120-catenin (p120ctn) interacts with E-cadherin, but to our knowledge, no formal proof that p120ctn functions as a bona fide tumor suppressor gene has emerged to date. We report herein that p120ctn loss leads to tumor development in mice. We have generated a conditional knockout model of p120ctn whereby mice develop preneoplastic and neoplastic lesions in the oral cavity, esophagus, and squamous forestomach. Tumor-derived cells secrete granulocyte macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor-α (TNFα). The tumors contain significant desmoplasia and immune cell infiltration. Immature myeloid cells comprise a significant percentage of the immune cells present and likely participate in fostering a favorable tumor microenvironment, including the activation of fibroblasts.

Ribozyme to TGF-β1 mRNA abrogates immunosuppressive effects of human colorectal adenocarcinoma HRT-18 cells in vitro and in vivo

Transforming growth factor-beta1 (TGF-beta1) is overexpressed in a variety of malignant epithelial tumors and was suggested to be a marker of colorectal cancer. Moreover, there is growing evidence that TGF-beta1 contributes to tumor progression by regulating tumor cell proliferation and differentiation, inducing a favorable tumor microenvironment, promoting migration and invasion, and suppressing macrophage cytotoxicity. Therefore, we stably transfected an anti-TGF-beta1 hammerhead ribozyme into the human colorectal adenocarcinoma cell line HRT-18. Expression of this ribozyme resulted in significant inhibition of TGF-beta1 expression on mRNA and protein level. This was associated with an enhanced tumor cell differentiation and a reduced tumor growth in vivo. The capability of tumor cells to suppress ROI production of co-cultivated human macrophages was abrogated in transfectants. Taken together, inhibition of TGF-beta1 in colorectal carcinoma cells might be an interesting therapeutic tool leading to reduced tumor cell growth and increased macrophage cytotoxicity. Thus, a gene-therapeutic approach using anti-TGF-beta1 ribozyme in combination with established anti-tumor agents is of great promise.

The role of SPARC in the TRAMP model of prostate carcinogenesis and progression

SPARC (Secreted Protein Acidic and Rich in Cysteine), is a matricellular glycoprotein that is produced by tumor and/or neighboring stroma. In human prostate cancer, SPARC immunoreactivity is highest in metastatic lesions but distinct contributions of tumoral and stromal SPARC to tumorigenesis and progression are unclear. To determine the role of SPARC in primary prostate tumorigenesis, we crossed SPARC-null (SP(-/-)) with TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice. TRAMP(+)/SP(-/-) mice exhibited accelerated cancer development and progression. Compared to their TRAMP(+)/SP(-/-) counterparts, TRAMP(+)/SP(+/+) tumors had fewer proliferating cells, and decreased cyclins A and D1 with increased p21(Cip) and p27(Kip). Similar effects on proliferation and cell-cycle regulators were observed in human prostate cancer cell lines, transiently transfected with pSPARC. TRAMP(+)/SP(-/-) tumors exhibited decreased stromal collagen, enhanced matrix metalloproteinase activity and increased vascular endothelial growth factor, proinflammatory cytokines. To determine the contribution of stromal SPARC, we evaluated subcutaneous tumor growth of TRAMP cell lines in syngeneic SP(+/+) and SP(-/-) mice. Enhanced growth, decreased stromal collagen and increased proteolysis were noted in SP(-/-) mice. Our findings demonstrate that both tumor and stromal SPARC are limiting for primary prostate tumorigenesis and progression, through effects on the cell cycle and the creation of a less favorable tumor microenvironment.