Quantification of B16 melanoma cells in lungs using triplex Q-PCR--a new approach to evaluate melanoma cell metastasis and tumor control

Nasal administration of recombinant Neospora caninum secreting IL-15/IL-15Rα inhibits metastatic melanoma development in lung

BACKGROUND

Metastases are the leading cause of mortality in many cancer types and lungs are one of the most common sites of metastasis alongside the liver, brain, and bones. In melanoma, 85% of late-stage patients harbor lung metastases. A local administration could enhance the targeting of metastases while limiting the systemic cytotoxicity. Therefore, intranasal administration of immunotherapeutic agents seems to be a promising approach to preferentially target lung metastases and decrease their burden on cancer mortality. From observations that certain microorganisms induce an acute infection of the tumor microenvironment leading to a local reactivating immune response, microbial-mediated immunotherapy is a next-generation field of investigation in which immunotherapies are engineered to overcome immune surveillance and escape from microenvironmental cancer defenses.

METHODS

The goal of our study is to evaluate the potential of the intranasal administration of Neospora caninum in a syngeneic C57BL6 mouse model of B16F10 melanoma lung metastases. It also compares the antitumoral properties of a wild-type N. caninum versus N. caninum secreting human interleukin (IL)-15 fused to the sushi domain of the IL-15 receptor α chain, a potent activator of cellular immune responses.

RESULTS

The treatment of murine lung metastases by intranasal administration of an N. caninum engineered to secrete human IL-15 impairs lung metastases from further progression with only 0,08% of lung surface harboring metastases versus 4,4% in wild-type N. caninum treated mice and 36% in untreated mice. The control of tumor development is associated with a strong increase in numbers, within the lung, of natural killer cells, CD8⁺ T cells and macrophages, up to twofold, fivefold and sixfold, respectively. Analysis of expression levels of CD86 and CD206 on macrophages surface revealed a polarization of these macrophages towards an antitumoral M1 phenotype.

CONCLUSION

Administration of IL-15/IL-15Rα-secreting N. caninum through intranasal administration, a non-invasive route, lend further support to N. caninum-demonstrated clear potential as an effective and safe immunotherapeutic approach for the treatment of metastatic solid cancers, whose existing therapeutic options are scarce. Combination of this armed protozoa with an intranasal route could reinforce the existing therapeutic arsenal against cancer and narrow the spectrum of incurable cancers.

β-Catenin signaling in alveolar macrophages enhances lung metastasis through a TNF-dependent mechanism

The main cause of malignancy-related mortality is metastasis. Although metastatic progression is driven by diverse tumor-intrinsic mechanisms, there is a growing appreciation for the contribution of tumor-extrinsic elements of the tumor microenvironment, especially macrophages, which correlate with poor clinical outcomes. Macrophages consist of bone marrow-derived and tissue-resident populations. In contrast to bone marrow-derived macrophages, the transcriptional pathways that govern the pro-metastatic activities of tissue-resident macrophages (TRMs) remain less clear. Alveolar macrophages (AMs) are a TRM population with critical roles in tissue homeostasis and metastasis. Wnt/β-catenin signaling is a hallmark of cancer and has been identified as a pathologic regulator of AMs in infection. We tested the hypothesis that β-catenin expression in AMs enhances metastasis in solid tumor models. Using a genetic β-catenin gain-of-function approach, we demonstrated that (a) enhanced β-catenin in AMs heightened lung metastasis; (b) β-catenin activity in AMs drove a dysregulated inflammatory program strongly associated with Tnf expression; and (c) localized TNF-α blockade abrogated this metastatic outcome. Last, β-catenin gene CTNNB1 and TNF expression levels were positively correlated in AMs of patients with lung cancer. Overall, our findings revealed a Wnt/β-catenin/TNF-α pro-metastatic axis in AMs with potential therapeutic implications against tumors refractory to the antineoplastic actions of TNF-α.

Quantitative Detection of Disseminated Melanoma Cells by Trp-1 Transcript Analysis Reveals Stochastic Distribution of Pulmonary Metastases

A better understanding of the process of melanoma metastasis is required to underpin the development of novel therapies that will improve patient outcomes. The use of appropriate animal models is indispensable for investigating the mechanisms of melanoma metastasis. However, reliable and practicable quantification of metastases in experimental mice remains a challenge, particularly if the metastatic burden is low. Here, we describe a qRT-PCR-based protocol that employs the melanocytic marker Trp-1 for the sensitive quantification of melanoma metastases in the murine lung. Using this protocol, we were able to detect the presence of as few as 100 disseminated melanoma cells in lung tissue. This allowed us to quantify metastatic burden in a spontaneous syngeneic B16-F10 metastasis model, even in the absence of visible metastases, as well as in the autochthonous Tg(Grm1)/Cyld^−/− melanoma model. Importantly, we also observed an uneven distribution of disseminated melanoma cells amongst the five lobes of the murine lung, which varied considerably from animal to animal. Together, our findings demonstrate that the qRT-PCR-based detection of Trp-1 allows the quantification of low pulmonary metastatic burden in both transplantable and autochthonous murine melanoma models, and show that the analysis of lung metastasis in such models needs to take into account the stochastic distribution of metastatic lesions amongst the lung lobes.

Efficacy of Targeted Radionuclide Therapy Using [131I]ICF01012 in 3D Pigmented BRAF- and NRAS-Mutant Melanoma Models and In Vivo NRAS-Mutant Melanoma

Simple Summary

Targeted radionuclide therapy (TRT) aims to selectively deliver radioactive molecules to tumor cells. For this purpose, we deliver iodine-131 ([¹³¹I]) to melanoma cells by using our laboratory-developed melanin specific radiotracer, the ICF01012. Approximately 50% and 20%–30% of human melanomas have activating mutation in BRAF or NRAS genes, respectively. These mutations lead to a constitutive activation of the MAPK/ERK pathway, which is known to be involved in tumor cells’ radioresistance. In this work, we showed using 3D in vitro tumor models, an additive efficiency of combining [¹³¹I]ICF01012-TRT and MAPK/ERK inhibitors in BRAF- and NRAS-mutant melanoma cells. In mice bearing NRAS^Q61K-mutated melanoma, TRT induced an impressive decrease in tumor growth, as well as a highly extended survival. Additionally, we showed that TRT reduces the metastatic capacity of melanoma, especially through lymph-node dissemination. These results are therefore of great interest, especially for patients with NRAS-mutant metastatic melanoma who currently lack specific efficient therapies.

Abstract

Purpose: To assess the efficiency of targeted radionuclide therapy (TRT), alone or in combination with MEK inhibitors (MEKi), in melanomas harboring constitutive MAPK/ERK activation responsible for tumor radioresistance. Methods: For TRT, we used a melanin radiotracer ([¹³¹I]ICF01012) currently in phase 1 clinical trial (NCT03784625). TRT alone or combined with MEKi was evaluated in three-dimensional melanoma spheroid models of human BRAF^V600E SK-MEL-3, murine NRAS^Q61K 1007, and WT B16F10 melanomas. TRT in vivo biodistribution, dosimetry, efficiency, and molecular mechanisms were studied using the C57BL/6J-NRAS^Q61K 1007 syngeneic model. Results: TRT cooperated with MEKi to increase apoptosis in both BRAF- and NRAS-mutant spheroids. NRAS^Q61K spheroids were highly radiosensitive towards [¹³¹I]ICF01012-TRT. In mice bearing NRAS^Q61K 1007 melanoma, [¹³¹I]ICF01012 induced a significant extended survival (92 vs. 44 days, p < 0.0001), associated with a 93-Gy tumor deposit, and reduced lymph-node metastases. Comparative transcriptomic analyses confirmed a decrease in mitosis, proliferation, and metastasis signatures in TRT-treated vs. control tumors and suggest that TRT acts through an increase in oxidation and inflammation and P53 activation. Conclusion: Our data suggest that [¹³¹I]ICF01012-TRT and MEKi combination could be of benefit for advanced pigmented BRAF-mutant melanoma care and that [¹³¹I]ICF01012 alone could constitute a new potential NRAS-mutant melanoma treatment.

The progression of metastatic melanoma augments a pro-oxidative milieu locally but not systemically

Malignant melanoma is the most dangerous form of skin cancer. Despite new therapies for melanoma treatment, effective therapy is mainly limited by excessive metastasis. Currently, the factors determining metastasis development are not elucidated, but oxidative stress was suggested to be involved. To this end, we analyzed oxidative stress parameters during the metastatic development using the syngeneic B16F10 melanoma model. An increase in blood plasma lipid peroxidation occurred at the earliest stage of the disease, with a progressive decrease in oxidative damage and an increase in antioxidant defense. Vice versa, increased lipid peroxidation and 3-nitrotyrosine, and decreased antioxidant parameters were observed in the metastatic nodules throughout the disease. This was concomitant with a progressive increase in vascular endothelial growth factor and proliferating cell nuclear antigen. We conclude that the oxidative stress in the bloodstream decreases during the metastatic process and that nitrosative stress increases during the proliferation and growth of metastatic nodules in the tumor microenvironment. These results will help to better understand the role of oxidative stress during melanoma metastasis.

Enhanced immunotherapeutic profile of oncolytic virus-based cancer vaccination using cyclophosphamide preconditioning

Despite a sizeable body of research, the efficacy of therapeutic cancer vaccines remains limited when applied as sole agents. By using a prime:boost approach involving two viral cancer vaccines, we were able to generate large tumor-specific CD8⁺ T-cell responses in a murine model of disseminated pulmonary melanoma. Significant increases in the number and quality of circulating effector T-cells were documented when low-dose cyclophosphamide (CTX) was administered pre-vaccination to tumor-bearing but not tumor-free hosts. Interestingly, tumor-bearing mice receiving CTX and co-primed with a melanoma differentiation antigen together with an irrelevant control antigen exhibited significantly enhanced immunity against the tumor, but not the control antigen, in secondary lymphoid organs. This result highlighted an increased cancer-specific reactivity of vaccine-induced T-cell responses following CTX preconditioning. Additionally, an acute reduction of the frequency of peripheral regulatory T-cells (Tregs) was noticeable, particularly in the proliferating, presumably tumour-reactive, subset. Enhanced infiltration of lungs with multifunctional T-cells resulted in overt reduction in metastatic burden in mice pretreated with CTX. Despite doubling the median survival in comparison to untreated controls, most vaccinated mice ultimately succumbed to cancer progression. However, preconditioning of the virus-based vaccination with CTX resulted in a remarkable improvement of the therapeutic activity leading to complete remission in the majority of the animals. Collectively, these data reveal how CTX can potentiate specific cellular immunity in an antigen-restricted manner that is only observed in vaccinated tumor-bearing hosts while depleting replicating Tregs. A single low dose of CTX enhances antitumor immunity and the efficacy of this potent prime:boost platform by modulating the kinetics of the vaccine-specific responses. Clinical assessment of CTX combined with next-generation cancer vaccines is indicated.

Vaccine-induced CD8 T cells are redirected with peptide-MHC class I-IgG antibody fusion proteins to eliminate tumor cells in vivo

Simulating a viral infection in tumor cells is an attractive concept to eliminate tumor cells. We previously reported the molecular design and the in vitro potency of recombinant monoclonal antibodies fused to a virus-derived peptide MHC class I complex that bypass the peptide processing and MHC loading pathway and directly displays a viral peptide in an MHC class I complex on the tumor cell surface. Here, we show that a vaccination-induced single peptide-specific CD8 T cell response was sufficient to eliminate B16 melanoma tumor cells in vivo in a fully immunocompetent, syngeneic mouse tumor model when mice were treated with mouse pMHCI-IgGs fusion proteins targeting the mouse fibroblast activation protein. Tumor growth of small, established B16 lung metastases could be controlled. The pMHCI-IgG had similar potency as an analogous pan-CD3 T-cell bispecific antibody. In contrast to growth control of small tumors, none of the compounds controlled larger solid tumors of MC38 cancer cells, despite penetration of pMHCI-IgGs into the tumor tissue and clear attraction and activation of antigen-specific CD8 T cells inside the tumor. pMHCI-IgG can have a similar potency as classical pan-T-cell recruiting molecules. The results also highlight the need to better understand immune suppression in advanced solid tumors.

C5a receptors C5aR1 and C5aR2 mediate opposing pathologies in a mouse model of melanoma

The canonical complement component 5a (C5a) receptor (C5aR) 1 has well-described roles in tumorigenesis but the contribution of the second receptor, C5aR2, is unclear. The present study demonstrates that B16.F0 melanoma cells express mRNA for both C5aR1 and C5aR2 and signal through ERK and p38 MAPKs in response to C5a. Despite this, C5a had no impact on melanoma cell proliferation or migration in vitro. In vivo studies demonstrated that the growth of B16.F0 melanoma tumors was increased in C5aR2^-/- mice but reduced in C5aR1^-/- mice and wild-type mice treated with a C5aR1 antagonist. Analysis of tumor-infiltrating leukocyte populations showed no significant differences between wild-type and C5aR2^-/- mice. Conversely, percentages of myeloid-derived suppressor cells, macrophages, and regulatory T lymphocytes were lower in tumors from C5aR1^-/- mice, whereas total (CD3⁺) T lymphocytes and CD4⁺ subsets were higher. Analysis of cytokine and chemokine levels also showed plasma IFN-γ was higher and tumor C-C motif chemokine ligand 2 was lower in the absence of C5aR1. The results suggest that C5aR1 signaling supports melanoma growth by promoting infiltration of immunosuppressive leukocyte populations into the tumor microenvironment, whereas C5aR2 has a more restricted but beneficial role in limiting tumor growth. Overall, these data support the potential of C5aR1-inhibitory therapies for melanoma.-Nabizadeh, J. A., Manthey, H. D., Panagides, N., Steyn, F. J., Lee, J. D., Li, X. X., Akhir, F. N. M., Chen, W., Boyle, G. M., Taylor, S. M., Woodruff, T. M., Rolfe, B. E. C5a receptors C5aR1 and C5aR2 mediate opposing pathologies in a mouse model of melanoma.

CD8+ T cells induced by adenovirus-vectored vaccine are capable of preventing establishment of latent murine γ-herpesvirus 68 infection

CD8+ T cells are known to control infections, but their role in preventing latent infection from establishing has not been thoroughly investigated. We hypothesized that a potent CD8+ T cell response patrolling the mucosal viral entry points could kill the first infected cells and thereby abrogate the infection before latency is established. To investigate this, replication deficient adenovirus serotype 5 vectors encoding murine γ-herpesvirus-68 CD8+ T cell epitopes linkedto the T cell adjuvant Invariant chain, were developed. We show that intranasal vaccination of mice reduces the risk of establishment of latent infection from multiple intranasal ID50 challenges with murine γ-herpesvirus-68 by 81% per exposure at 14 days post vaccination. Protection waned over time, but immune responses were extended by heterologous prime-boost vaccination applied simultaneously intramuscularly and intranasally, and animals vaccinated 66 days prior to challenge showed a strong trend of long-term protection. Our data provides evidence that CD8+ T cells are able to protect against establishment of latent infection. Although the protective efficacy is difficult to maintain over time, this proof-of-concept study suggests a role for a CD8+ T cell arm in future vaccine strategies against latent human viral infections caused by pathogens such as HIV and multiple herpes virus.

Quantifying spontaneous metastasis in a syngeneic mouse melanoma model using real time PCR

Modeling metastasis in vivo with animals is a priority for both revealing mechanisms of tumor dissemination and developing therapeutic methods. While conventional intravenous injection of tumor cells provides an efficient and consistent system for studying tumor cell extravasation and colonization, studying spontaneous metastasis derived from orthotopic tumor sites has the advantage of modeling more aspects of the metastatic cascade, but is challenging as it is difficult to detect small numbers of metastatic cells. In this work, we developed an approach for quantifying spontaneous metastasis in the syngeneic mouse B16 system using real time PCR. We first transduced B16 cells with lentivirus expressing firefly luciferase Luc2 gene for bioluminescence imaging. Next, we developed a real time quantitative PCR (qPCR) method for the detection of luciferase-expressing, metastatic tumor cells in mouse lungs and other organs. To illustrate the approach, we quantified lung metastasis in both spontaneous and experimental scenarios using B16F0 and B16F10 cells in C57BL/6Ncrl and NOD-Scid Gamma (NSG) mice. We tracked B16 melanoma metastasis with both bioluminescence imaging and qPCR, which were found to be self-consistent. Using this assay, we can quantitatively detect one Luc2 positive tumor cell out of 10⁴ tissue cells, which corresponds to a metastatic burden of 1.8 × 10⁴ metastatic cells per whole mouse lung. More importantly, the qPCR method was at least a factor of 10 more sensitive in detecting metastatic cell dissemination and should be combined with bioluminescence imaging as a high-resolution, end-point method for final metastatic cell quantitation. Given the rapid growth of primary tumors in many mouse models, assays with improved sensitivity can provide better insight into biological mechanisms that underpin tumor metastasis.

Beta-glucan-induced inflammatory monocytes mediate antitumor efficacy in the murine lung

β-Glucan is a naturally occurring glucose polysaccharide with immunostimulatory activity in both infection and malignancy. β-Glucan's antitumor effects have been attributed to the enhancement of complement receptor 3-dependent cellular cytotoxicity, as well as modulation of suppressive and stimulatory myeloid subsets, which in turn enhances antitumor T cell immunity. In the present study, we demonstrate antitumor efficacy of yeast-derived β-glucan particles (YGP) in a model of metastatic-like melanoma in the lung, through a mechanism that is independent of previously reported β-glucan-mediated antitumor pathways. Notably, efficacy is independent of adaptive immunity, but requires inflammatory monocytes. YGP-activated monocytes mediated direct cytotoxicity against tumor cells in vitro, and systemic YGP treatment upregulated inflammatory mediators, including TNFα, M-CSF, and CCL2, in the lungs. Collectively, these studies identify a novel role for inflammatory monocytes in β-glucan-mediated antitumor efficacy, and expand the understanding of how this immunomodulator can be used to generate beneficial immune responses against metastatic disease.

Contribution of NK cells to immunotherapy mediated by PD-1/PD-L1 blockade

Checkpoint blockade immunotherapy targeting the PD-1/PD-L1 inhibitory axis has produced remarkable results in the treatment of several types of cancer. Whereas cytotoxic T cells are known to provide important antitumor effects during checkpoint blockade, certain cancers with low MHC expression are responsive to therapy, suggesting that other immune cell types may also play a role. Here, we employed several mouse models of cancer to investigate the effect of PD-1/PD-L1 blockade on NK cells, a population of cytotoxic innate lymphocytes that also mediate antitumor immunity. We discovered that PD-1 and PD-L1 blockade elicited a strong NK cell response that was indispensable for the full therapeutic effect of immunotherapy. PD-1 was expressed on NK cells within transplantable, spontaneous, and genetically induced mouse tumor models, and PD-L1 expression in cancer cells resulted in reduced NK cell responses and generation of more aggressive tumors in vivo. PD-1 expression was more abundant on NK cells with an activated and more responsive phenotype and did not mark NK cells with an exhausted phenotype. These results demonstrate the importance of the PD-1/PD-L1 axis in inhibiting NK cell responses in vivo and reveal that NK cells, in addition to T cells, mediate the effect of PD-1/PD-L1 blockade immunotherapy.

Personalized Cancer Vaccine Platform for Clinically Relevant Oncolytic Enveloped Viruses

The approval of the first oncolytic virus for the treatment of metastatic melanoma and the compiling evidence that the use of oncolytic viruses can enhance cancer immunotherapies targeted against various immune checkpoint proteins has attracted great interest in the field of cancer virotherapy. We have developed a novel platform for clinically relevant enveloped viruses that can direct the virus-induced immune response against tumor antigens. By physically attaching tumor-specific peptides onto the viral envelope of vaccinia virus and herpes simplex virus 1 (HSV-1), we were able to induce a strong T cell-specific immune response toward these tumor antigens. These therapeutic peptides could be attached onto the viral envelope by using a cell-penetrating peptide sequence derived from human immunodeficiency virus Tat N-terminally fused to the tumor-specific peptides or, alternatively, therapeutic peptides could be conjugated with cholesterol for the attachment of the peptides onto the viral envelope. We used two mouse models of melanoma termed B16.OVA and B16-F10 for testing the efficacy of OVA SIINFEKL-peptide-coated viruses and gp100-Trp2-peptide-coated viruses, respectively, and show that by coating the viral envelope with therapeutic peptides, the anti-tumor immunity and the number of tumor-specific CD8+ T cells in the tumor microenvironment can be significantly enhanced.

Biomaterial scaffolds for non-invasive focal hyperthermia as a potential tool to ablate metastatic cancer cells

Currently, there are very few therapeutic options for treatment of metastatic disease, as it often remains undetected until the burden of disease is too high. Microporous poly(ε-caprolactone) biomaterials have been shown to attract metastasizing breast cancer cells in vivo early in tumor progression. In order to enhance the therapeutic potential of these scaffolds, they were modified such that infiltrating cells could be eliminated with non-invasive focal hyperthermia. Metal disks were incorporated into poly(ε-caprolactone) scaffolds to generate heat through electromagnetic induction by an oscillating magnetic field within a radiofrequency coil. Heat generation was modulated by varying the size of the metal disk, the strength of the magnetic field (at a fixed frequency), or the type of metal. When implanted subcutaneously in mice, the modified scaffolds were biocompatible and became properly integrated with the host tissue. Optimal parameters for in vivo heating were identified through a combination of computational modeling and ex vivo characterization to both predict and verify heat transfer dynamics and cell death kinetics during inductive heating. In vivo inductive heating of implanted, tissue-laden composite scaffolds led to tissue necrosis as seen by histological analysis. The ability to thermally ablate captured cells non-invasively using biomaterial scaffolds has the potential to extend the application of focal thermal therapies to disseminated cancers.

Therapeutic effects of tyroserleutide on lung metastasis of human hepatocellular carcinoma SK-HEP-1 and its mechanism affecting ICAM-1 and MMP-2 and -9

BACKGROUND

Tyroserleutide (YSL) inhibits the growth and metastasis of human hepatocellular carcinoma (HCC). This paper studied the effect of YSL on metastasis of human HCC and investigated its mechanisms.

METHODS

In vivo, experimental lung metastasis models of human HCC SK-HEP-1 cells in nude mice were established, and In vitro, the proliferation, adhesion and invasion of SK-HEP-1 cells were detected.

RESULTS

In vivo, YSL significantly inhibited the metastasis of human HCC. In vitro, YSL significantly inhibited the proliferation, adhesion and invasion of SK-HEP-1 cells. Through analyses with reverse transcription PCR (RT-PCR) and Western blot, we observed that YSL significantly inhibited the expressions of ICAM-1 in SK-HEP-1 cells. Through RT-PCR, Western blot and zymography methods, YSL was discovered to decrease the mRNA level, protein expression and activity of MMP-2 and -9 in SK-HEP-1 cells.

CONCLUSION

We concluded that YSL could inhibit tumor growth and metastasis of human HCC SK-HEP-1 cells.

CXCR3+ monocytes/macrophages are required for establishment of pulmonary metastases

We present a new foundational role for CXCR3⁺ monocytes/macrophages in the process of tumor engraftment in the lung. CXCR3 is associated with monocytic and lymphocytic infiltration of inflamed or tumor-bearing lung. Although the requirement for tumor-expressed CXCR3 in metastatic engraftment has been demonstrated, the role of monocyte-expressed CXCR3 had not been appreciated. In a murine model of metastatic-like melanoma, engraftment was coordinate with CXCR3⁺ monocyte/macrophage accumulation in the lungs and was sensitive to pharmacologic inhibition of CXCR3 signaling. Tumor engraftment to lung was impaired in CXCR3^−/− mice, and transient reconstitution with circulating CXCR3-replete monocytes was sufficient to restore engraftment. These data illustrate the paradoxical pro-tumor role for CXCR3 in lung immunobiology wherein the CXCR3 axis drives both the anti-tumor effector cell chemoattraction and pro-tumor infiltration of the lungs and suggests a potential therapeutic target for lung-tropic metastasizing cancers.