S-adenosylmethionine blocks tumorigenesis and with immune checkpoint inhibitor enhances anti-cancer efficacy against BRAF mutant and wildtype melanomas

S-Adenosylmethionine: A Multifaceted Regulator in Cancer Pathogenesis and Therapy

S-adenosylmethionine (SAMe) is a key methyl donor that plays a critical role in a variety of cellular processes, such as DNA, RNA and protein methylation, essential for maintaining genomic stability, regulating gene expression and maintaining cellular homeostasis. The involvement of SAMe in cancer pathogenesis is multifaceted, as through its multiple cellular functions, it can influence tumor initiation, progression and therapeutic resistance. In addition, the connection of SAMe with polyamine synthesis and oxidative stress management further underscores its importance in cancer biology. Recent studies have highlighted the potential of SAMe as a biomarker for cancer diagnosis and prognosis. Furthermore, the therapeutic implications of SAMe are promising, with evidence suggesting that SAMe supplementation or modulation could improve the efficacy of existing cancer treatments by restoring proper methylation patterns and mitigating oxidative damage and protect against damage induced by chemotherapeutic drugs. Moreover, targeting methionine cycle enzymes to both regulate SAMe availability and SAMe-independent regulatory effects, particularly in methionine-dependent cancers such as colorectal and lung cancer, presents a promising therapeutic approach. Additionally, exploring epitranscriptomic regulations, such as m6A modifications, and their interaction with non-coding RNAs could enhance our understanding of tumor progression and resistance mechanisms. Precision medicine approaches integrating patient subtyping and combination therapies with chemotherapeutics, such as decitabine or doxorubicin, together with SAMe, can enhance chemosensitivity and modulate epigenomics, showing promising results that may improve treatment outcomes. This review comprehensively examines the various roles of SAMe in cancer pathogenesis, its potential as a diagnostic and prognostic marker, and its emerging therapeutic applications. While SAMe modulation holds significant promise, challenges such as bioavailability, patient stratification and context-dependent effects must be addressed before clinical implementation. In addition, better validation of the obtained results into specific cancer animal models would also help to bridge the gap between research and clinical practice.

Anti-PD-1 amplifies costimulation in melanoma-infiltrating Th1-like Foxp3+ regulatory T cells to alleviate local immunosuppression

BACKGROUND

Immune checkpoint inhibitors targeting programmed cell death protein-1 (PD-1) are the first line of treatment for many solid tumors including melanoma. PD-1 blockade enhances the effector functions of melanoma-infiltrating CD8+ T cells, leading to durable tumor remissions. However, 55% of patients with melanoma do not respond to treatment. As Foxp3+ regulatory T (Treg) cells play an important role in tumor-induced immunosuppression and express PD-1, we hypothesized that anti-PD-1 also increases the functions of melanoma-infiltrating Treg cells, which could be detrimental to treatment efficacy.

METHODS

The cellular and functional dynamics of Treg cells were evaluated in C57Bl/6 Foxp3-reporter mice bearing highly immunogenic and PD-1 blockade-sensitive Yale University Mouse Melanoma Exposed to Radiation 1.7 (YUMMER1.7) tumors. Treg cell responses in tumors and lymphoid compartments were examined throughout tumor growth or therapy and were assessed ex vivo by multiparametric flow cytometry analysis, with in vitro suppression assays using tumor-infiltrating lymphocytes isolated by fluorescence-activated cell sorting (FACS) and in situ through spatial proteomic and transcriptomic profiling.

RESULTS

In this highly immunogenic melanoma model, anti-PD-1 monotherapy yielded high responders (HRs) and low responders (LRs). We show that the potent CD8+ T cell responses characteristic of HR tumors paradoxically coincide with the expansion of highly-activated, Helios-expressing Treg cells. In both HRs and LRs, Treg cells co-localize with CD8+ T cells in immunogenic regions of the tumor and display potent suppressive capacity in vitro. Further characterization revealed that melanoma-infiltrating Treg cells progressively acquire T-bet and interferon gamma expression, exclusively in HRs, and induction of this T helper cell 1 (Th1)-like phenotype in vitro led to CD8+ T cell evasion from Treg cell-mediated suppression. Using spatial proteomic and transcriptomic profiling, we demonstrate that Treg cells display an increased activity of PI3K/Akt signaling in regions of HR tumors with an elevated CD8:Treg cell ratio.

CONCLUSIONS

PD-1 blockade promotes the expansion of a subset of highly-activated Treg cells coexpressing PD-1 and Helios. While these cells are potently suppressive outside tumor environments, costimulatory and inflammatory signals present in the tumor microenvironment lead to their local acquisition of Th1-like characteristics and loss of suppression of effector T cells.

Metabolic insights into tumor lymph node metastasis in melanoma

Although accounting for only a small amount of skin cancers, melanoma contributes prominently to skin cancer-related deaths, which are mostly caused by metastatic diseases, and lymphatic metastasis constitutes the main route. In this review, we concentrate on the metabolic mechanisms of tumor lymph node (LN) metastasis in melanoma. Two hypotheses of melanoma LN metastasis are introduced, which are the premetastatic niche (PMN) and parallel progression model. Dysregulation of oxidative stress, lactic acid concentration, fatty acid synthesis, amino acid metabolism, autophagy, and ferroptosis construct the metabolic mechanisms in LN metastasis of melanoma. Moreover, melanoma cells also promote LN metastasis by interacting with non-tumor cells through metabolic reprogramming in TIME. This review will deepen our understanding of the mechanism of lymph node metastasis in melanoma.

SMG5 Inhibition Restrains Hepatocellular Carcinoma Growth and Enhances Sorafenib Sensitivity

Hepatocellular carcinoma (HCC) has a pathogenesis that remains elusive with restricted therapeutic strategies and efficacy. This study aimed to investigate the role of SMG5, a crucial component in nonsense-mediated mRNA decay (NMD) that degrades mRNA containing a premature termination codon, in HCC pathogenesis and therapeutic resistance. We demonstrated an elevated expression of SMG5 in HCC and scrutinized its potential as a therapeutic target. Our findings revealed that SMG5 knockdown not only inhibited the migration, invasion, and proliferation of HCC cells but also influenced sorafenib resistance. Differential gene expression analysis between the control and SMG5 knockdown groups showed an upregulation of methionine adenosyltransferase 1A in the latter. High expression of methionine adenosyltransferase 1A, a catalyst for S-adenosylmethionine (SAM) production, as suggested by The Cancer Genome Atlas data, was indicative of a better prognosis for HCC. Further, an ELISA showed a higher concentration of SAM in SMG5 knockdown cell supernatants. Furthermore, we found that exogenous SAM supplementation enhanced the sensitivity of HCC cells to sorafenib alongside changes in the expression of Bax and Bcl-2, apoptosis-related proteins. Our findings underscore the important role of SMG5 in HCC development and its involvement in sorafenib resistance, highlighting it as a potential target for HCC treatment.

S-Adenosylmethionine (SAM) diet promotes innate immunity via histone H3K4me3 complex

S-adenosylmethionine (SAM) was a methyl donor for modifying histones, which had crucial roles in lipid accumulation, tissue injury, and immune responses. SAM fluctuation might be linked to variations in histone methylation. However, the underlying molecular mechanisms of whether the SAM diet influenced the immune response via histone modification remained obscure. In this study, we utilized the Caenorhabditis elegans as a model to investigate the role of SAM diet in innate immunity. We found that 50 μM SAM increased resistance to Gram-negative pathogen Pseudomonas aeruginosa PA14 by reducing the bacterial burden in the intestine. Furthermore, through the genetic screening in C. elegans, we found that SAM functioned in germline to enhance innate immunity via an H3K4 methyltransferase complex to upregulate the immune response genes, including irg-1 and T24B8.5. Intriguingly, SAM also protected mice from P. aeruginosa PA14 infection by reducing the bacterial burden in lung. These findings provided insight into the mechanisms of molecular connections among SAM diet, histone modifications and innate immunity.

BRAF Mutations in Melanoma: Biological Aspects, Therapeutic Implications, and Circulating Biomarkers

Melanoma is an aggressive form of skin cancer resulting from the malignant transformation of melanocytes. Recent therapeutic approaches, including targeted therapy and immunotherapy, have improved the prognosis and outcome of melanoma patients. BRAF is one of the most frequently mutated oncogenes recognised in melanoma. The most frequent oncogenic BRAF mutations consist of a single point mutation at codon 600 (mostly V600E) that leads to constitutive activation of the BRAF/MEK/ERK (MAPK) signalling pathway. Therefore, mutated BRAF has become a useful target for molecular therapy and the use of BRAF kinase inhibitors has shown promising results. However, several resistance mechanisms invariably develop leading to therapeutic failure. The aim of this manuscript is to review the role of BRAF mutational status in the pathogenesis of melanoma and its impact on differentiation and inflammation. Moreover, this review focuses on the mechanisms responsible for resistance to targeted therapies in BRAF-mutated melanoma and provides an overview of circulating biomarkers including circulating tumour cells, circulating tumour DNA, and non-coding RNAs.

The abscopal effect of anti-CD95 and radiotherapy in melanoma

BACKGROUND

Radiotherapy (RT) is frequently adopted to control cancer cell proliferation, which is achieved by altering the tumor microenvironment (TME) and immunogenicity. Apoptosis of cancer cells is the major effect of radiation on tumor tissues. Fas/APO-1(CD95) receptors on the cell membrane are death receptors that can be activated by diverse factors, including radiation and integration with CD95L on CD8⁺ T cells. The abscopal effect is defined as tumor regression out of the local RT field, and it is produced through anti-tumor immunity. The immune response against the radiated tumor is characterized by the cross-presentation between antigen-presenting cells (APCs), which includes cytotoxic T cells (CTLs) and dendritic cells (DCs).

METHODS

The effect of activation and radiation of CD95 receptors on melanoma cell lines was examined in vivo and in vitro. In vivo, bilateral lower limbs were given a subcutaneous injection of a dual-tumor. Tumors in the right limb were radiated with a single dose of 10 Gy (primary tumor), while tumors in the left limb (secondary tumor) were spared.

RESULTS

The anti-CD95 treatment plus radiation (combination treatment) reduced growth rates of both primary and secondary tumors relative to the control or radiation groups. In addition, higher degrees of infiltrating CTLs and DCs were detected in the combination treatment compared to the other groups, but the immune response responsible for secondary tumor rejection was not proven to be tumor specific. In vitro, combination treatment combined with radiation resulted in further apoptosis of melanoma cells relative to controls or cells treated with radiation.

CONCLUSIONS

Targeting CD95 on cancer cells will induce tumor control and the abscopal effect.