Methionine enkephalin activates autophagy and stimulates tumour cell immunogenicity in human cutaneous squamous cell carcinoma

In vitro and in vivo killing effects of methionine enkephalin on osteosarcoma

OBJECTIVE

This study aimed to investigate the underlying regulatory effects of methionine enkephalin (MENK) on osteosarcoma.

METHODS

The Cell Counting Kit-8 assay, clone formation, wound healing, transwell assay, and flow cytometry were performed to measure the effects of MENK on the proliferation, migration, invasion, and apoptosis of MG-63 and Saos-2 cells. Opiate growth factor receptor expression (OGFr) in cells was stably knocked down using siRNA. A tumor model was established by inoculating MG-63 cells into mice. Flow cytometry was performed to identify alterations in mice bone marrow, spleen, and tumor tissue immune cells. The phenotype of tumor-associated macrophages was determined using immunohistochemistry. After OGFr knockdown or/and treatment with MENK, Bax, Bcl-2, caspase 3, caspase 9, and PARP expression levels were characterized using qRT-PCR, western blot, and WES, respectively.

RESULTS

MENK could significantly inhibit the proliferation, invasion, and migration of MG-63 and Saos-2, arrest the cell cycle in the G0/G1 phase, upregulate Bax, caspase 3, caspase 9, and PARP expression, and downregulate Bcl-2 expression. Tumor size and weight were lower in the MENK group than those in the control group. MENK-treated mice exhibited a reduced ratio of CD11b + Gr-1 + myeloid-derived suppressor cells. MENK increased the ratio of M1-type macrophages and decreased the proportion of M2-type macrophages in tumor tissue. Furthermore, the level of TNF-α significantly increased while that of IL-10 decreased in MENK-treated mice. The effect of MENK could be partly reversed by OGFr knockdown.

CONCLUSION

MENK reduces the abundance of myeloid-derived suppressor cells, induces M1 polarization of macrophages, and exhibits an inhibitory effect on osteosarcoma.

Methionine enkephalin inhibited cervical cancer migration as well as invasion and activated CD11b+ NCR1+ NKs of tumor microenvironment

This study was to study the role of methionine enkephalin (menk) in cell invasion and migration as well as NK cells activation of tumor microenvironment in cervical cancer. The results showed that menk inhibited cervical cancer migration and invasion. In addition, we found menk affected epithelial to mesenchymal transition (EMT) related indicators, with increasing E-cadherin level, decreasing N-cadherin and vimentin level. Through in vivo mouse model, we found that menk IFNγ and NKP46 expression was upregulated in tumor tissues by menk compared with controls, while LAG3 expression was inhibited by menk, besides, there was an upregulation of CD11b+ NCR1+ NKs of tumor microenvironment in cervical cancer. Therefore, we concluded that menk inhibited cancer migration and invasion via affecting EMT related indicators and activated CD11b+ NCR1+ NKs of tumor microenvironment in cervical cancer, laying a theoretical foundation for the further clinical treatment of menk.

Involvement of the Opioid Peptide Family in Cancer Progression

Peptides mediate cancer progression favoring the mitogenesis, migration, and invasion of tumor cells, promoting metastasis and anti-apoptotic mechanisms, and facilitating angiogenesis/lymphangiogenesis. Tumor cells overexpress peptide receptors, crucial targets for developing specific treatments against cancer cells using peptide receptor antagonists and promoting apoptosis in tumor cells. Opioids exert an antitumoral effect, whereas others promote tumor growth and metastasis. This review updates the findings regarding the involvement of opioid peptides (enkephalins, endorphins, and dynorphins) in cancer development. Anticancer therapeutic strategies targeting the opioid peptidergic system and the main research lines to be developed regarding the topic reviewed are suggested. There is much to investigate about opioid peptides and cancer: basic information is scarce, incomplete, or absent in many tumors. This knowledge is crucial since promising anticancer strategies could be developed alone or in combination therapies with chemotherapy/radiotherapy.

Methionine enkephalin inhibits colorectal cancer by remodeling the immune status of the tumor microenvironment

There is evidence that methionine enkephalin (MENK), an opioid peptide, promotes anti-tumor immune responses. In this study, the effect of MENK on colorectal cancer (CRC) and its mechanisms of action were examined in vivo. The intraperitoneal administration of 20 mg/kg MENK effectively inhibited MC38 subcutaneous colorectal tumor growth in mice. MENK inhibited tumor progression by increasing the immunogenicity and recognition of MC38 cells. MENK down-regulated the oncogene Kras and anti-apoptotic Bclxl and Bcl2, suppressed Il1b, Il6, iNOS, and Arg1 (encoding inflammatory cytokines), and increased Il17a and Il10 levels. MENK promoted a tumor suppressive state by decreasing the immune checkpoints Pd-1, Pd-l1, Lag3, Flgl1, and 2b4 in CRC. MENK also altered the immune status of the tumor immune microenvironment (TIME). It increased the infiltration of M1-type macrophages, CD8⁺T cells, and CD4⁺T cells and decreased the proportions of G-MDSCs, M-MDSCs, and M2-type macrophages. MENK accelerated CD4⁺T_EM and CD8⁺T_EM cell activation in the TIME and up-regulated IFN-γ, TNF-α, and IL-17A in CD4⁺T cells and Granzyme B in CD8⁺T cells. In addition, analyses of PD-1 and PD-L1 expression indicated that MENK promoted the anti-tumor immune response mediated by effector T cells. Finally, OGFr was up-regulated at the protein and mRNA levels by MENK, and the inhibitory effects of MENK on tumor growth were blocked by NTX, a specific blocker of OGFr. These finding indicate that MENK remodels the TIME in CRC to inhibit tumor progression by binding to OGFr. MENK is a potential therapeutic agent for CRC, especially for improving the efficacy of immunotherapy.

Opioidergic Signaling-A Neglected, Yet Potentially Important Player in Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin diseases, the prevalence of which is especially high among children. Although our understanding about its pathogenesis has substantially grown in recent years, and hence, several novel therapeutic targets have been successfully exploited in the management of the disease, we still lack curative treatments for it. Thus, there is an unmet societal demand to identify further details of its pathogenesis to thereby pave the way for novel therapeutic approaches with favorable side effect profiles. It is commonly accepted that dysfunction of the complex cutaneous barrier plays a central role in the development of AD; therefore, the signaling pathways involved in the regulation of this quite complex process are likely to be involved in the pathogenesis of the disease and can provide novel, promising, yet unexplored therapeutic targets. Thus, in the current review, we aim to summarize the available potentially AD-relevant data regarding one such signaling pathway, namely cutaneous opioidergic signaling.

Regulatory role of methionine enkephalin in myeloid-derived suppressor cells and macrophages in human cutaneous squamous cell carcinoma

The antitumor effects of methionine enkephalin (MENK), also known as opioid growth factor (OGF), including its inhibitory effects on cutaneous squamous cell carcinoma (CSCC), have been established. In this study, we determined the precise mechanism by which MENK suppresses CSCC cell growth. In particular, MENK induced G0/G1 cell cycle arrest and promoted apoptosis in CSCC cells via the Bcl-2/Bax/Caspase-3 signaling pathway. Moreover, MENK reduced immunosuppression by downregulating the number of myeloid-derived suppressor cells (MDSCs) and regulating the polarization of tumor-associated macrophages from M2 to M1 in vivo. Furthermore, JAK2/STAT3, an important tumor-promotion and immunosuppression signaling pathway that is involved in MDSC expansion in tumors and macrophage polarization, was inhibited. These findings highlight the potential of the JAK2/STAT3 signaling pathway as a therapeutic target and suggest the clinical application of MENK for CSCC.