Mouse Melanoma Cell Line B16F10 Research Articles

Tyrosinase regulates the motility of human melanoma cell line A375 through its hydroxylase enzymatic activity

Melanoma, originating from melanocytes, is a highly aggressive tumor. Tyrosinase is involved in melanin production in melanocytes, and its overexpression is noted in malignant melanomas. However, the role of tyrosinase in melanomas remains unclear. Therefore, this study aimed to evaluate the potential functions of tyrosinase in the human melanoma cell line A375. The expression level of tyrosinase in A375 cells was undetectable. However, markedly increased expression level was observed in the mouse melanoma cell line B16F10 and the human melanoma cell line WM266-4. Subsequently, we investigated the effect of ectopic tyrosinase expression on A375 cell motility using wound-healing assay. The overexpression of tyrosinase resulted in enhanced cell migration in both stable and transient tyrosinase expression cells. The levels of filamentous actin were decreased in tyrosinase-expressing A375 cells, suggesting that tyrosinase regulates cell motility by modulating actin polymerization. Histidine residues in tyrosinase are important for its enzymatic activity for synthesizing melanin. Substitution of these histidine residues to alanine residues mitigated the promotion of tyrosinase-induced A375 cell metastasis. Furthermore, melanin treatment enhanced A375 cell metastasis and phosphorylation of Cofilin. Thus, our findings suggest that tyrosinase increases the migration of A375 cells by regulating actin polymerization through its enzymatic activity.

Low-dose imiquimod induces melanogenesis in melanoma cells through an ROS-mediated pathway

BackgroundMelanogenesis is the process of melanin maturation which not only protects skin from UV radiation but also plays an important role in antigenicity of melanomas. Imiquimod (IMQ) is a toll-like receptor 7 (TLR7) agonist that exhibits antiviral and anticancer activity. ObjectiveTo explore whether IMQ could induce melanogenesis in melanoma cells. MethodsThe mouse melanoma cell line B16F10, the mouse immortalized melanocyte Melan-A, and human melanoma cell lines MNT-1, C32 and A375 were utilized in this study. The pigmented level was observed by the centrifuged cell pellet. The intracellular and extracellular melanin levels were examined in the absorbance in NaOH-extracted cell lysate and cell-cultured medium, respectively. The expression of melanogenesis related proteins was examined by immunoblotting. The intracellular cyclic AMP amount was evaluated by the cAMP Glo assay kit. The activity of phosphodiesterase 4B (PDE4B) was investigated by CREB reporter assay with overexpressed PDE4B or not. ResultsWe demonstrated that a low dose of IMQ could trigger melanogenesis in B16F10 cells. IMQ induced microphthalmia-associated transcription factor (MITF) nuclear translocation, upregulated the expression of melanogenesis-related proteins, increased tyrosinase (TYR) activity, and led to pigmentation in B16F10 cells. Next, we found that IMQ-induced melanogenesis was activated by excessive intracellular cAMP accumulation, which was regulated through IMQ-mediated PDE4B inhibition. Finally, IMQ-induced ROS production was found to be involved in melanogenesis by its control of PDE4B activity. ConclusionsLow dose of IMQ could activate melanogenesis through the ROS/PDE4B/PKA pathway in melanoma cells.

Anticancer Potential of Novel Nanoemulgel Formulations in Melanoma

Melanoma is classified as one of the most common cancers with an increasing incidence rate and the conventional treatment options that come with undesirable effects decrease the life quality of patients. Herein, as an alternative therapy option for systemic administration, Carbopol-based nanoemulgel formulations for local delivery were designed. Topical drug delivery systems containing Oxaliplatin, a cisplatin derivative anticancer drug used in the treatment of colorectal cancers, were evaluated for their potential for melanoma treatment. Nanoemulgel formulations with particle size under 300 nm were prepared and characterized in terms of droplet size, zeta potential and liquid crystal formation. The viscosity, as a critical attribute for topical drug delivery systems, was also evaluated, and pseudoplastic behavior of these novel drug delivery systems were confirmed. The controlled drug release pattern was shown with in vitro drug release studies with a significant difference from oxaliplatin when applied in solution. In vitro cell viability evaluation with L929 mouse fibroblast cell line confirmed the biocompatibility of prepared formulations, and the anticancer effect of novel nanoemulgel formulations were presented in B16-F10 mouse melanoma cell line. In conclusion, the anticancer potential of Oxaliplatin nanoemulgels were shown in vitro as a therapy option for melanoma, and the advantages of emulsion and gel-based drug delivery systems were combined in a nanotechnology platform for effective and patient-friendly application of an anticancer therapy for melanoma.

Phenolic from apple blossom "Hongro" inhibits the expression of proteins related to melanogenesis in B16F10 melanoma cells.

This study aimed to assess apple blossom extracts as potential natural whitening agents due to their ability to inhibit melanogenesis. Ethanol extracts of apple blossom (ABE) were assessed for biological activity in the B16F10 mouse melanoma cell line. ABE toxicity was assessed by thiazolyl blue tetrazolium bromide (MTT) assay. Levels of melanogenic enzyme expression in response to ABE supplementation were assessed by western blotting. Also assessed purified kaempferol, one of the phenolic compounds extracted from apple blossom, was evaluated using western blot analysis. The expression levels of cellular tyrosinase, microphthalmia-associated transcription factor (MITF), tyrosinase-related protein (TRP)-1, and TRP-2 proteins related to melanogenesis decreased in a dose-dependent manner with ABE treatment of cells. Using nuclear magnetic resonance, we identified kaempferol in the ABE. Treatment of cells with purified kaempferol decreased the expression levels of tyrosinase and the MITF protein to a similar degree as that observed with ABE treatment. This suggests that the efficacy of melanogenesis-related inhibition demonstrated by ABE was due to kaempferol. ABE has an inhibitive effect on melanogenic enzymes and potentially can be applied to functional foods and cosmetics having a whitening effect as a natural material.

Imiquimod-induced ROS production causes lysosomal membrane permeabilization and activates caspase-8-mediated apoptosis in skin cancer cells

BackgroundLysosomal cell death is induced by lysosomal membrane permeabilization (LMP) and the subsequent release of lysosomal proteolytic enzymes, including cathepsins (CTSs), which results in mitochondrial dysfunction and apoptosis. Imiquimod (IMQ), a synthetic TLR7 ligand, has both antiviral and antitumor activity against various skin malignancies in clinical treatment. Previously, we demonstrated IMQ not only caused lysosomal dysfunction but also triggered lysosome biogenesis to achieve lysosomal adaptation in cancer cells. ObjectiveTo determine whether lysosomes are involved in IMQ-induced apoptosis. MethodsThe human skin cancer cell lines BCC, A375 and mouse melanoma cell line B16F10 were used in all experiments. Cell death was determined by the Cell Counting Kit-8 (CCK-8) assay and DNA content assay. Protein expression was determined by immunoblotting. Caspase-8 activity was assessed using a fluorescence caspase-8 kit and determined by flow cytometry and confocal microscopy. ResultsIMQ not only induced lysosome damage but also abrogated lysosome function in skin cancer cells. IMQ-induced caspase-8 activation contributed to the processes of lysosomal cell death. Moreover, the use of ROS scavengers significantly abolished caspase-8 activation and inhibited IMQ-induced LMP. Additionally, pharmacological inhibition of CTSD not only abrogated caspase-8 activation but also rescued IMQ-induced cell death. Finally, lysosome-alkalizing agents enhanced the cytotoxicity of IMQ in vitro and in vivo. ConclusionsIMQ-induced ROS accumulation promotes LMP, releases CTSs into the cytosol, stimulates caspase-8 activation and finally causes lysosomal cell death. Lysosomal cell death and the CTSD/caspase-8 axis may play a crucial role in IMQ-induced cell death.

Serotonin (5-HT) 2A Receptor Involvement in Melanin Synthesis and Transfer via Activating the PKA/CREB Signaling Pathway

The 5-HT2A serotonin receptor (HTR2A) has been reported to be involved in the serotonin- or serotonin receptor 2A agonist-induced melanogenesis in human melanoma cells. However, the molecular mechanisms underlying HTR2A in regulating melanogenesis remain poorly understood. In this research, cultured mouse melanoma cell line B16F10, human skin, and zebrafish embryos were used to elucidate the downstream signaling of HTR2A in regulating melanogenesis and to verify the potential application of HTR2A in the treatment of pigment-associated cutaneous diseases. We demonstrated that HTR2A antagonists (AT1015 and ketanserin) attenuated the melanogenesis induction of serotonin in both mouse melanoma cells and zebrafish embryos. The agonists of HTR2A (DOI and TCB-2) increased melanin synthesis and transfer in B16F10 cells, human skin tissue, and zebrafish embryos. Furthermore, the HTR2A agonists increased the expression of proteins related to melanosome organization and melanocyte dendrites to facilitate the melanocyte migration and melanosome transport. HTR2A antagonists and genetic knockout of zebrafish htr2aa (the homologue of mammalian HTR2A gene) were also used to clarify that HTR2A mediates serotonin and DOI in regulating melanogenesis. Finally, through small scale screening of the candidate downstream pathway, we demonstrated that HTR2A mediates the melanogenesis induction of its ligands by activating the PKA/CREB signaling pathway. In this research, we further confirmed that HTR2A is a crucial protein to mediate melanocyte function. Meanwhile, this research supports that HTR2A could be designed as a drug target for the development of chemicals to treat cutaneous diseases with melanocytes or melanogenesis abnormality.

EPITHELIAL-MESENCHYMAL TRANSITION IN MELANOMA PROGRESSION: THE CONTRIBUTION OF ADAPTOR PROTEIN RUK/CIN85

The purpose of this study was to test the hypothesis that Ruk/CIN85 overexpression/knockdown in melanoma cells may be involved in the regulation of EMT. Materials and methods. The mouse melanoma cell line B16-F10 and its sublines with up-/down-regulation of Ruk/CIN85 (generated early using lentiviral technology) were used as a model for research. Melanoma cells were cultured in the complete RPMI 1610 medium under standard conditions. Proliferative activity of the cells was estimated using the MTT-test, and cell migratory potential was studied by the wound-healing assay. The data obtained were analyzed with parametric Student`s t-test. Results were expressed as mean ± SEM and significance was set at P<0.05. Results and Discussion. Cutaneous melanoma genesis is a multi-step process initiated by the transformation of a normal melanocyte following an oncogenic insult. Due to the transcriptome and metabolome reprogramming in the course of EMT, transformed melanoma cells change their phenotype and acquire increased proliferative rate, cell motility, invasiveness, and metastatic potential. According to the data obtained, overexpression of Ruk/CIN85 in B16 mouse melanoma cells (subclones Up7 and Up21) led to an increase in their proliferative activity by 1,6 and 1.8 times, respectively, at 24th hour in comparison with control Mock cells . At the 48th hour, when the cells reached confluence, the cell viability of subclones did not differ from the control ones. No statistically significant changes in the proliferative activity of B16 cells with suppressed expression of the adaptor protein (subclone Down) were found. In accordance with previous data, B16 cells overexpressing Ruk/CIN85 were characterized by strongly increased motility rate (more than twofold for both Up7 and Up21 subclones compared to control Mock cells). At the same time, knockdown of Ruk/CIN85 in B16 cells resulted in a decrease in their migratory activity by about 30%. Conclusions. All findings obtained demonstrated that the malignancy traits of melanoma B16 cells are inversely modulated upon up- and down-changes in adaptor protein Ruk/CIN85 expression levels suggesting its possible role in the control of EMT.

Isolation and Fluorescent Labeling of Extracellular Vesicles from Cultured Tumor Cells.

Extracellular vesicles (EVs), comprising exosomes, ectosomes, and apoptotic bodies, are an important component of molecular cell-to-cell communication, and are critically involved in the pathophysiology of various diseases, including tumors. In order to study the interaction of tumor cell-derived EVs with their target cells and to investigate their biological functions in comparison to other tumor cell-released factors, efficient isolation of EVs from cultured tumor cells, as well as fluorescent labeling of these EVs, is often necessary. In addition, EVs and EV-like particles are emerging as versatile vehicles for the delivery of therapeutic substances. Here, we describe an easy size exclusion chromatography-based method to isolate EVs from the mouse melanoma cell line B16F10 that yields highly enriched EV samples for subsequent applications such as molecular and functional studies. Our protocol also includes an optional labeling step with the lipophilic dye DiD, which allows tracking of EV uptake by recipient cells in vitro and in vivo.

Targeted Nanotherapeutics Using LACTB Gene Therapy Against Melanoma.

Introductionβ-lactamase (LACTB) is a tumor suppressor gene in various tumors including melanoma. However, it remains challenging to efficiently deliver the LACTB gene into melanoma. Recently, we designed a nonviral nanocarrier iRGD/DOTAP/MPEG-PDLLA (iDPP) that could deliver gene targetedly to melanoma efficiently without obvious adverse effects.MethodsIn this study, the tumor-targeted nanoparticle iDPP was prepared to deliver LACTB gene to treat melanoma in vitro and in vivo. First, the expression level of LACTB in 6 clinical specimens of melanoma patients was evaluated. Subsequently, the characteristics of iDPP/LACTB nanocomplexes were studied. Afterwards, the in vitro and in vivo anti-tumor efficacy of the iDPP/LACTB nanocomplexes were explored utilizing the B16-F10 mouse melanoma cell line and the B16-F10 subcutaneous melanoma model.ResultsCompared with the normal epithelium, the expression level of LACTB in melanoma tissues was significantly downregulated. In vitro B16-F10 cell tests showed iDPP/LACTB nanocomplexes could increase the mRNA levels of P21, Bid, Bax, Pidd1, and Sival genes and up-regulate the p53 signaling pathway of melanoma cells, thus promoting cell apoptosis and blocking the cell cycle. Injected intravenously, iDPP nanoparticles could deliver DNA to the subcutaneous melanoma targetedly. Based on in vivo mouse xenograft model, iDPP/LACTB nanocomplexes could effectively inhibit tumor proliferation and induce tumor apoptosis, thus significantly inhibiting melanoma growth (tumor inhibition rate is about 68%) in the subcutaneous B16-F10 melanoma model.ConclusionThe downregulated LACTB might be a potential target for melanoma therapy. The iDPP/LACTB nanocomplexes could inhibit the growth of the mouse melanoma without obvious side effects, which provide a new option for melanoma gene therapy research.

Therapeutic combination silencing VEGF and SOX10 increases the antiangiogenic effect in the mouse melanoma model B16-F10 - in vitro and in vivo studies.

IntroductionGene therapy is an innovative form of treatment of genetic diseases, in which psiRNA molecules silencing specific genes are applied.AimThe study evaluated the anti-tumour effect of psiRNA silencing preparations of the vascular endothelial growth factor (VEGF) and Sry-related HMG-Box gene 10 (SOX10) on melanoma (B16-F10) by inhibiting angiogenesis.Material and methodsThe preparations based on plasmid vectors psiRNA silencing the gene SOX10 and VEGF that form complexes with cationic lipid (psiRNA/carrier) have been developed. psiRNA preparations were tested on the mouse melanoma cell line B16-F10, both in vitro and in vivo. The silencing activity of transfected melanoma cells with the obtained psiRNA preparations was examined using the qPCR and Western blot methods. The anti-tumour activity of psiRNA preparations on melanoma tumour cells was then evaluated in a mouse in vivo model.Results In vitro studies have shown that the B16-F10 cells efficiently transfect non-viral preparations – psiRNA: Lyovec (74–89%). Worth mentioning is the fact that silencing SOX10 in B16-F10 melanoma cells increases the expression of the COL18A1 gene (compared to the preparation inhibiting only VEGF), which codes the endostatin to stop angiogenesis. In vivo results show that the level of haemoglobin in tumours of mice treated with psiRNA formulations was over 6 times lower than controls and tumour mass was 60-80% lower.ConclusionsThe novel study proves that simultaneous inhibition of SOX10 and VEGF enhances the antiangiogenic action and thus contributes to a significant halt of disease development. In addition, these data expand knowledge about SOX10 regulation and functions.

Therapeutic Efficacy of Carbon Ion Irradiation Enhanced by 11-MUA-Capped Gold Nanoparticles: An in vitro and in vivo Study.

PurposeGold nanoparticles (AuNPs) are widely studied as radiosensitizers, but their radiosensitization in carbon ion radiotherapy is unsatisfactory. There is a lack of in vivo data on the radiosensitization of AuNPs under carbon ion irradiation. This study focused on the radiosensitization effect of AuNPs in the mouse melanoma cell line B16-F10 in vitro and in vivo.Materials and Methods11-mercaptoundecanoic acid (11-MUA)-coated gold (Au) nanoparticles (mAuNPs) formulations were prepared and characterized. To verify the radiosensitization effect of mAuNPs, hydroxyl radicals were generated in aqueous solution, and the detection of intracellular reactive oxygen species (ROS) and clone survival were carried out in vitro. The tumor growth rate (TGR) and survival of mice were analyzed to verify the radiosensitization effect of mAuNPs in vivo. The apoptosis of tumor cells was detected, and the expression of key proteins in the apoptosis pathway was verified by immunohistochemistry.ResultsThe intracellular ROS level in B16-F10 cells was enhanced by mAuNPs under carbon ion irradiation. The sensitization rate of mAuNPs was 1.22 with a 10% cell survival rate. Compared with irradiation alone, the inhibitory effect of mAuNPs combined with carbon ion irradiation on tumor growth was 1.94-fold higher, the survival time of mice was prolonged by 1.75-fold, and the number of apoptotic cells was increased by 1.43-fold. The ratio of key proteins Bax and Bcl2 in the apoptosis pathway was up-regulated, and the expression of caspase-3, a key executor of the apoptosis pathway, was up-regulated.ConclusionIn in vivo and in vitro experiments, mAuNPs showed radiosensitivity to carbon ion irradiation. The sensitization effect of mAuNPs on mice tumor may be achieved by activating the mitochondrial apoptosis pathway and increasing tumor tissue apoptosis. To our best knowledge, the present study is the first in vivo evidence for radiosensitization of mAuNPs in tumor-bearing mice exposed to carbon ion irradiation.

In Vitro Effects of Selective COX and LOX Inhibitors and Their Combinations with Antineoplastic Drugs in the Mouse Melanoma Cell Line B16F10.

The constitutive expression or overactivation of cyclooxygenase (COX) and lipoxygenase (LOX) enzymes results in aberrant metabolism of arachidonic acid and poor prognosis in melanoma. Our aim is to compare the in vitro effects of selective COX-1 (acetylsalicylic acid), COX-2 (meloxicam), 5-LOX (MK-886 and AA-861), 12-LOX (baicalein) and 15-LOX (PD-146176) inhibition in terms of proliferation (SRB assay), mitochondrial viability (MTT assay), caspase 3-7 activity (chemiluminescent assay), 2D antimigratory (scratch assay) and synthesis of eicosanoids (EIA) in the B16F10 cell line (single treatments). We also explore their combinatorial pharmacological space with dacarbazine and temozolomide (median effect method). Overall, our results with single treatments show a superior cytotoxic efficacy of selective LOX inhibitors over selective COX inhibitors against B16F10 cells. PD-146176 caused the strongest antiproliferation effect which was accompanied by cell cycle arrest in G1 phase and an >50-fold increase in caspases 3/7 activity. When the selected inhibitors are combined with the antineoplastic drugs, only meloxicam provides clear synergy, with LOX inhibitors mostly antagonizing. These apparent contradictions between single and combination treatments, together with some paradoxical effects observed in the biosynthesis of eicosanoids after FLAP inhibition in short term incubations, warrant further mechanistical in vitro and in vivo scrutiny.

CD133 Antigen as a Potential Marker of Melanoma Stem Cells: In Vitro and In Vivo Studies.

Melanoma is the most dangerous type of skin cancer. Cancer stem cells (CSCs) are suspected to be responsible for the cancer recurrence and in the consequence for cancer therapy failure. CD133 is a potential marker for detection of melanoma CSCs. Experiments were performed on the B16-F10 mouse melanoma cell line. CD133+ cells were isolated using an immunomagnetic cell sorting technique. After isolation proliferative and clonogenic potential of CD133+, CD133- and CD133+/- were evaluated. The potential of CD133+ and CD133- cells for tumor induction was conducted on C57BL/6J mouse model. Three different cell quantities (100, 1000, 10000) were tested. Tumor morphology, number of mitoses, and tumor necrosis area were analyzed. Average 0.12% CD133+ cells were isolated. Compared to CD133- and unsorted CD133+/- cells, CD133+ cells were characterized by the higher proliferative and clonogenic potential. These properties were not confirmed in vivo, as both CD133+ and CD133- cells induced tumor growth in mouse model. No statistical differences in mitosis number and tumor necrosis area were observed. Simultaneous detection of CD133 antigen with other markers is necessary for accurate identification of these melanoma cancer stem cells.

α-MSH-PE38KDEL Kills Melanoma Cells via Modulating Erk1/2/MITF/TYR Signaling in an MC1R-Dependent Manner.

Background/ObjectiveThe immunotoxin α-MSH-PE38KDEL consisting of α-MSH and PE38KDEL showed high cytotoxicity on MSH receptor-positive melanoma cells, suggesting that α-MSH-PE38KDEL might be a potent drug for the treatment of melanoma. Herein, we explored whether the Erk1/2/MITF/TYR signaling, a verified target of α-MSH/MC1R, was involved in α-MSH-PE38KDEL-mediated cytotoxicity.MethodsHuman melanoma cell line A375, mouse melanoma cell line B16-F10, human breast cancer cell line MDA-MB-231 and human primary epidermal melanocytes (HEMa) with different expression levels of MC1R were used in this study. Cell apoptosis and viability were determined by using flow cytometry and MTT assays. Protein expressions were tested by Western blotting.ResultsThe expression levels of MC1R in A375 and B16-F10 cells were significantly higher than that of MDA-MB-231 and HEMa. α-MSH-PE38KDEL treatment induced a significant inhibition in cell viability in A375 and B16-F10 cells, while showed no obvious influence in the viability of MDA-MB-231 and HEMa cells. However, knockdown of MC1R abolished α-MSH-PE38KDEL role in promoting cell apoptosis in A375 and B16-F10 cells, and upregulation of MC1R endowed α-MSH-PE38KDEL function to promote cell apoptosis in MDA-MB-231 and HEMa cells. Additionally, α-MSH-PE38KDEL treatment increased the phosphorylation levels of Erk1/2 and MITF (S73), and decreased MITF and TYR expressions in an MC1R-dependent manner. All of the treatments, including inhibition of Erk1/2 with PD98059, MC1R downregulation and MITF overexpression weakened the anti-tumor role of α-MSH-PE38KDEL in melanoma.ConclusionCollectively, this study indicates that α-MSH-PE38KDEL promotes melanoma cell apoptosis via modulating Erk1/2/MITF/TYR signaling in an MC1R-dependent manner.

Abstract 2746: PET-CT/FACS platform to detect the biodistribution of radioisotope 89Zr PD-1 inhibitor in syngeneic tumor models

Abstract Cancer treatment has been revolutionized by targeting the interaction between tumors and immune system. For instance, PD-1/PD-L1 mono- or combo-therapy has achieved great success in clinics, and patient responsiveness is closed associated with PD-L1 expression in cancer cells, tumor infiltration leukocytes, and drug bio-distribution in the tumor microenvironment. We established a method to label PD-1 inhibitor with radioisotope 89Zr for in-life imaging (PET-CT). Anti-PD-1 sensitive mouse colorectal cell line MC38 and resistant mouse melanoma cell line B16F10 were implanted to C57BL/6 mice, which were then treated with 89Zr PD-1 inhibitor. PET imaging was performed at multiple time points to detect the bio-distribution of anti-PD-1, while the infiltrated immune cells were identified by FCM and PD-L1 expression measured by IHC. Notable tumor uptake of 89Zr PD-1 inhibitor was observed in mouse liver and tumor grafts. The uptake in tumor increased over time and plateaued 24 hours post-injection. MC38 and B16F10 tumor grafts showed difference in uptake levels. Blood and tumor at both flanks were removed for leucocyte phenotyping, and compared with B16F10, MC-38 tumors exhibited higher percentage of total lymphocytes and cytotoxic T lymphocytes, equivalent number of dendritic cells and less myeloid cells. Further phenotyping indicates that compared to MC-38, B16F10 tumors contain higher percentage of MDSC, most of which are monocytic myeloid derived suppressor cells. With our PET-CT/FACS platform, we can evaluate immunotherapy response and microenvironment changes in different tumors in “one-mouse” system. The unique immune microenvironment (high TIL, high CD8+ T and low MDSC) may contribute to the notable and sustainable uptake of PD-1 inhibitor and the corresponding efficacy. This system can act as a good translational platform to monitor the PK-PD readout of immune therapy. Citation Format: Xuzhen Tang, Fuyang Wang, Junyi Chen, Xuanming Zeng, Zhibo Liu, Qunsheng Ji. PET-CT/FACS platform to detect the biodistribution of radioisotope 89Zr PD-1 inhibitor in syngeneic tumor models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2746.

Studies on the inhibitory mechanisms of baicalein in B16F10 melanoma cell proliferation

Baicalein induces the formation of superoxide and hydroxyl radicals via 12-lipoxygenase (12-LOX) in the B16F10 mouse melanoma cell line; baicalein also causes a reduction in cellular viability and induces cell apoptosis. In this study, we utilized ROS scavengers to evaluate the role of ROS in baicalein-induced cell death and used the 12-LOX downstream product, 12-hydroxyeicosatetraenoic acid (12-HETE), to counterbalance the 12-LOX-inhibitory action of baicalein. ROS scavengers had no effect on cell differentiation, but in the cellular viability (MTT) assay, ROS scavengers effectively reversed cell viability reduction induced by baicalein. A Western blot analysis revealed that the ROS scavengers had no effect on the cell apoptosis protein, active caspase-3. From the aspect of 12-LOX, 12-HETE had no effect on cell differentiation, but it effectively reversed the reduction in cellular viability caused by baicalein in B16F10 cells. 12-HETE also possessed an inhibitory effect on the increase in expression of active caspase-3 caused by baicalein. Combined pretreatment with ROS scavengers and 12-HETE minimized the damage caused by baicalein. The majority of cell death occurring in response to baicalein-induced ROS formation in B16F10 mouse melanoma was due to cell necrosis. Cell apoptosis due to 12-LOX suppression by baicalein only accounted for a small portion.

Abstract A79: Inhibition of p53-MDM2 protein interaction reduces tumor growth in a mouse melanoma model

Abstract Tumor suppressor protein p53 is mutated in close to 50% of human tumors. Under steady state conditions, the two E3 ligases MDM2 and MDM4 interact with and inhibit the transcriptional activity of p53. Inhibition of p53-MDM2/4 interaction to reactivate p53 has therefore been considered a therapeutic strategy. In this study, we tested p53-MDM2 protein-protein interaction inhibition using the small molecule AMG 232, which is currently being tested in phase 1b/2a clinical trials. In vitro, AMG 232 induced a significant, p53-dependent growth arrest in the mouse melanoma cell line B16-F10. Using mass spectrometry-based proteomics, we identified differential protein expression patterns following AMG 232 treatment of B16-F10 melanoma cells. In vivo, the growth of B16-F10 melanoma cells implanted in WT C57BL/6 mice was significantly reduced by AMG 232 treatment. Our data demonstrate that AMG 232 induces a p53-dependent tumor growth arrest in an immunocompetent mouse model, and we are currently testing whether AMG232 can synergize with checkpoint immunotherapy. Citation Format: Katrine Ingelshed, Danai Lianoudaki, Dilraj Lama, Silke Sohn, Nicolas Fritz, Long Jiang, Fredrik Wermeling, Mikael Karlsson, David P. Lane, Saikiran K. Sedimbi. Inhibition of p53-MDM2 protein interaction reduces tumor growth in a mouse melanoma model [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A79.

Abstract 1485: Hepatic cell cycle-related kinase shapes a metastatic-prone liver microenvironment via crosstalk between myeloid-derived suppressor cell and natural killer T cell

Abstract Metastasis is a prominent cause of cancer-related death governed by both cancer cell-intrinsic mechanisms and extrinsic microenvironment. Clinical observations demonstrated liver as a common metastatic site for various cancers, which may be due to its immune tolerant environment. Myeloid-derived suppressor cell (MDSC) is a heterogeneous cell population of immature myeloid cells that contribute to the formation of a favorable metastatic environment partially via suppression of immune effector cells. However, the underlying mechanisms in liver tropism of tumor metastasis remain poorly understood. We have previously discovered that cell cycle-related kinase (CCRK) can promote primary hepatocellular carcinoma (HCC) development via MDSCs (Gut 2018; Nat Commun accepted). Here we hypothesize that the accumulation of hepatic MDSCs induced by CCRK may contribute to the formation of a favorable metastatic liver microenvironment. By the construction of a liver-specific CCRK inducible transgenic (TG) mouse model by a Cre/loxP system, induction of CCRK expression by tamoxifen injection could increase CD11b+Gr-1+Ly6G+Ly6Clow polymorphonuclear (PMN)-MDSCs liver accumulation specifically in male mice with upregulated Cxcl1 and Gcsf expression. Intrahepatic injection of a mouse hepatoma cell line Hep1-6 in male TG mice developed larger tumors compared to control and positively associated with increased PMN-MDSCs levels in liver. Moreover, the tumorigenicity was abolished by PMN-MDSC depletion. Notably, intrasplenic injection of a mouse melanoma cell line B16F10 exhibited increased level of liver-infiltrating PMN-MDSCs and enhanced liver metastasis in male TG mice compared to control mice. Moreover, depletion of PMN-MDSCs suppressed metastasis in liver. Mechanistically, anti-tumor NKT cells, rather than NK cells and CD8+T cells, were negatively correlated with tumor weight and MDSC proportion, indicating the potential crosstalk between MDSC and NKT in liver metastasis. Our findings suggest that hepatic CCRK expression create a tumor growth- and metastasis-supportive liver microenvironment via enhancing immunosuppression. Additional colorectal cancer metastasis models will be evaluated in our established TG mice. Moreover, the roles and underlying mechanisms of CCRK-PMN-MDSC interactions in the establishment of liver metastasis await further investigation. This project is supported by Collaborative Research Fund C4017-14G and the Focused Innovations Scheme 1907309. Citation Format: Xuezhen ZENG, Jingying Zhou, Zhewen Xiong, Hanyong Sun, Weiqin Yang, Wenshu Tang, Yu Feng, Alfred Sze-Lok Cheng. Hepatic cell cycle-related kinase shapes a metastatic-prone liver microenvironment via crosstalk between myeloid-derived suppressor cell and natural killer T cell [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1485.

A New Tetrahydrofuran Lignan from Premna serratifolia Wood

Phytochemical investigation of the CHCl3 extract of Premna serratifolia (syn: P. integrifolia) wood collected in Myanmar led to the isolation of a new tetrahydrofuran type lignan, 7,9-dihydroxydolichanthin B (1), together with two known triterpenoids, oleanonic acid (2) and (2a, 3α)-dihydroxyolean-12-en-28-oic acid (3). The structure of the new compound was determined using various spectroscopic techniques, mainly 1D- and 2D-NMR, HRESIMS, IR, and optical rotation, and by comparisons with the reported literatures. Compounds 1-3 had anti-melanin deposition activities against IBMX and α-MSH induced B16-F10 mouse melanoma cell line with IC50 values of 18.4, 17.7 and 11.2 μM, respectively. However, 2 exhibited cytotoxicity at concentrations above 50 μM.

Lignans with melanogenesis effects from Premna serratifolia wood

Three new lignoids, premnan A (1), premnan B (2), and tauntangyiol C (3), were isolated from Premna serratifolia wood, a traditional cosmetic plant in Myanmar, together with a new lignoid, premnan C (4) assumed to be an artifact, one natural new lignoid (5), and three known lignoids (6–8). The structures of the new compounds 1–4 were elucidated based on 1D and 2D NMR, IR spectroscopy, and HRESIMS. The absolute configurations of 1–4 were also determined by optical rotation, circular dichroism (CD) data analyses, and comparisons with the reported literature. All isolated compounds were tested for their melanogenesis activities against the B16-F10 mouse melanoma cell line. Compounds 1 and 4 showed melanogenesis enhancing activities of 31% and 50%, respectively, at a 50 μM concentration. Compounds 2, 3, and 6 increased melanin production by 67%, 30%, and 45%, respectively, at a 100 μM concentration, without any cytotoxicity.