BACKGROUND: Until 2021, colon cancer was a leading cancer globally. Early detection improves outcomes; however, advanced cases still having poor prognosis. Therefore, an understanding of associated molecular mechanisms is crucial for developing new preventive and therapeutic strategies for colon cancer.
METHODS: The TCGA database was analyzed to assess melanocortin 1receptor (MC1R) expression in colon cancer and its link with patient prognosis. Further, models and diverse experimental techniques were employed to investigate the impact of MC1R on colon cancer progression and its underlying mechanism was elucidated.
RESULTS: In a follow-up study of clinical patients, the important role of MC1R was identified in the development of colon cancer. First, MC1R was expressed more highly in colon tumor tissues than in adjacent tissues. In addition, MC1R was associated with colon cancer prognosis, and higher expression of MC1R tended to predict a worse prognosis. This conclusion was verified in MC1R-/- mice, which showed a greater resistance to tumor growth than wild-type mice, as expected. Further investigation revealed a significant change in the portion of Tregs in MC1R-/- mice, while the portion of CD4 + and CD8 + T cells remained unchanged. The in vitro experiments revealed a weaker ability of the MC1R-/- T cells to differentiate into Tregs. Previous studies report that the functional integrity of Tregs is interwoven with cellular metabolism. Therefore, MC1R was deduced to regulate the differentiation of Tregs by reprogramming the metabolism. As expected, MC1R-/- T cells exhibited weaker mitochondrial function and a lower aerobic oxidation capacity. Concurrently, the MC1R-/- T cells had stronger limiting effects on colon cancer cells. According to these results, the MC1R inhibitor was hypothesized as a potential therapeutic agent to suppress colon cancer. The results showed that upon MC1R suppression, the tumors in the mice developed more slowly, and the mice survived longer, potentially providing a novel strategy to treat clinical colon cancer.
CONCLUSIONS: By regulating Tregs differentiation, MC1R overexpression in colon cancer correlates with poor prognosis, while MC1R inhibition shows potential as a therapeutic approach to slow tumor growth and enhance survival.

Abnormal melanogenesis can lead to hyperpigmentation. Tyrosinase (TYR), a key rate-limiting enzyme in melanin production, is an important therapeutic target for these disorders. We investigated the TYR inhibitory activity of hydrolysates extracted from the muscle tissue of Takifugu flavidus (TFMH). We used computer-aided virtual screening to identify a novel peptide that potently inhibited melanin synthesis, simulated its binding mode to TYR, and evaluated functional efficacy in vitro and in vivo. TFMH inhibited the diphenolase activities of mTYR, reducing TYR substrate binding activity and effectively inhibiting melanin synthesis. TFMH indirectly reduced cAMP response element-binding protein phosphorylation in vitro by downregulating melanocortin 1 receptor expression, thereby inhibiting expression of the microphthalmia-associated transcription factor, further decreasing TYR, tyrosinase related protein 1, and dopachrome tautomerase expression and ultimately impeding melanin synthesis. In zebrafish, TFMH significantly reduced black spot formation. TFMH (200 μg/mL) decreased zebrafish TYR activity by 43% and melanin content by 52%. Molecular dynamics simulations over 100 ns revealed that the FGFRSP (T-6) peptide stably binds mushroom TYR via hydrogen bonds and ionic interactions. T-6 (400 μmol/L) reduced melanin content in B16F10 melanoma cells by 71% and TYR activity by 79%. In zebrafish, T-6 (200 μmol/L) inhibited melanin production by 64%. TFMH and T-6 exhibit good potential for the development of natural skin-whitening cosmetic products.

The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system has been widely used to create animal models for biomedical and agricultural use owing to its low cost and easy handling. However, the occurrence of erroneous cleavage (off-targeting) may raise certain concerns for the practical application of the CRISPR-Cas9 system. In this study, we created a melanocortin 1 receptor (MC1R)-edited pig model through somatic cell nuclear transfer (SCNT) by using porcine kidney cells modified by the CRISPR-Cas9 system. We then carried out whole-genome sequencing of two MC1R-edited pigs and two cloned wild-type siblings, together with the donor cells, to assess the genome-wide presence of single-nucleotide variants and small insertions and deletions (indels) and found only one candidate off-target indel in both MC1R-edited pigs. In summary, our study indicates that the minimal off-targeting effect induced by CRISPR-Cas9 may not be a major concern in gene-edited pigs created by SCNT.

Hair heterochromia may be caused by different mechanisms. At clinical work, we found a Chinese boy whose hair colour gradually turned to red. We record the diagnosis and treatment process and follow-up situation, finally find that altered hair colour phenotype is due to MC1R genetic mutations, rather than zinc deficiency. This rarely red hair colour phenotype improve our understanding of hair heterochromia caused by genetic mutations.

Traumatic brain injury (TBI) is a common disease worldwide with high mortality and disability rates. Besides the primary mechanical injury, the secondary injury associated with TBI can also induce numerous pathological changes, such as brain edema, nerve apoptosis, and neuroinflammation, which further aggravates neurological dysfunction and even causes the death due to the primary injury. Among them, neuronal apoptosis is a key link in the injury. Melanocortin-1 receptor (MC1R) is a G protein coupled receptor, belonging to the melanocortin receptor family. Studies have shown that activation of MC1R inhibits oxidative stress and apoptosis, and confers neuroprotective effects against various neurological diseases. Merlin is a protein product of the NF2 gene, which is widely expressed in the central nervous system (CNS) of mice, rats, and humans. Studies have indicated that Merlin is associated with MC1R. In this study, we explored the anti-apoptotic effects and potential mechanisms of MC1R. A rat model of TBI was established through controlled cortical impact. The MC1R-specific agonist Nle4-D-Phe7-α-Melanocyte (NDP-MSH) and the inhibitor MSG-606 were employed to explore the effects of MC1R and Merlin following TBI and investigated the associated mechanisms. The results showed that the expression levels of MC1R and Merlin were upregulated after TBI, and activation of MC1R promoted Merlin expression. Further, we found that MC1R activation significantly improved neurological dysfunction and reduced brain edema and neuronal apoptosis induced by TBI in rats. Mechanistically, its neuroprotective function and anti-apoptotic were partly associated with MC1R activation. In conclusion, we demonstrated that MC1R activation after TBI may inhibit apoptosis and confer neuroprotection by upregulating the expression of Merlin.

Coat color, as a distinct phenotypic characteristic of pigs, is often subject to preference and selection, such as in the breeding process of new breed. Shanxia long black pig was derived from an intercross between Berkshire boars and Licha black pig sows, and it was bred as a paternal strain with high-quality meat and black coat color. Although the coat color was black in the F1 generation of the intercross, it segregated in the subsequent generations. This study aims to decode the genetic basis of coat color segregation and develop a method to distinct black pigs from the spotted in Shanxia long black pig.
Only a QTL was mapped at the proximal end of chromosome 6, and MC1R gene was picked out as functional candidate gene. A total of 11 polymorphic loci were identified in MC1R gene, and only the c.67_68insCC variant was co-segregating with coat color. This locus isn\'t recognized by any restriction endonuclease, so it can\'t be genotyped by PCR-RFLP. The c.370G > A polymorphic locus was also significantly associated with coat color, and has been in tightly linkage disequilibrium with the c.67_68insCC. Furthermore, it is recognized by BspHI. Therefore, a PCR-RFLP method was set up to genotype this locus. Besides the 175 sequenced individuals, another more 1,391 pigs were genotyped with PCR-RFLP, and all of pigs with GG (one band) were black.
MC1R gene (c.67_68insCC) is the causative gene (mutation) for the coat color segregation, and the PCR-RFLP of c.370G > A could be used in the breeding program of Shanxia long black pig.

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Inhibition of T cell infiltration dampens antitumor immunity and causes resistance to immune checkpoint blockade (ICB) therapy. By in vivo CRISPR screening in B16F10 melanoma in female mice, here we report that loss of melanocortin-1 receptor (MC1R) in melanoma cells activates antitumor T cell response and overcomes resistance to ICB. Depletion of MC1R from another melanocytic melanoma model HCmel1274 also enhances ICB efficacy. By activating the GNAS-PKA axis, MC1R inhibits interferon-gamma induced CXCL9/10/11 transcription, thus impairing T cell infiltration into the tumor microenvironment. In human melanomas, high MC1R expression correlates with reduced CXCL9/10/11 expression, impaired T cell infiltration, and poor patient prognosis. Whereas MC1R activation is restricted to melanoma, GNAS activation by hotspot mutations is observed across diverse cancer types and is associated with reduced CXCL9/10/11 expression. Our study implicates MC1R as a melanoma immunotherapy target and suggests GNAS-PKA signaling as a pan-cancer oncogenic pathway inhibiting antitumor T cell response.

Without affecting cell viability, epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), theaflavine-3,3\'-digallate (TFDG), or theasinensin A (TSA) have been found to effectively reduce intracellular melanin content and tyrosinase (TYR) activity. However, studies on the anti-melanogenic mechanism of the above samples remain weak, and the activities of these samples in regulating melanogenesis at the molecular level lack comparison. Using B16F10 cells with the α-melanocyte-stimulating hormone (α-MSH) stimulation and without the α-MSH stimulation as models, the effects of EGCG, GCG, TFDG, or TSA on cell phenotypes and expression of key targets related to melanogenesis were studied. The results showed that α-MSH always promoted melanogenesis with or without adding the four samples. Meanwhile, the anti-melanogenic activities of the four samples were not affected by whether the α-MSH was added in the medium or not and the added time of the α-MSH. On this basis, the 100 µg/mL EGCG, GCG, TFDG, or TSA did not affect the TYR catalytic activity but inhibited melanin formation partly through downregulating the melanocortin 1 receptor (MC1R), microphthalmia-associated transcription factor (MITF), and the TYR family. The downregulation abilities of catechins on the TYR family and MITF expression were stronger than those of dimers at both the transcription and translation levels, while the ability of dimers to downregulate the MC1R expression was stronger than that of catechins at both the transcription and translation levels to some extent. The results of molecular docking showed that these four samples could stably bind to MC1R protein. Taken together, this study offered molecular mechanisms for the anti-melanogenic activity of the EGCG, GCG, TFDG, and TSA, as potential effective components against the UV-induced tanning reactions, and a key target (MC1R) was identified.

Obesity has emerged as a global issue, but with the complex structures of multiple related important targets and their agonists or antagonists determined, the mechanism of ligand-protein interaction may offer new chances for developing new generation agonists anti-obesity. Based on the molecule surface of the cryo-EM protein structure 7AUE, we tried to replace D-Ala3 with D-Met in setmelanotide as the linker site for fragment-growing with De novo evolution. The simulation results indicate that the derivatives could improve the binding abilities with the melanocortin 4 receptor and the selectivity over the melanocortin 1 receptor. The improved selectivity of the newly designed derivatives is mainly due to the shape difference of the molecular surface at the orthosteric peptide-binding pocket between melanocortin 4 receptor and melanocortin 1 receptor. The new extended fragments could not only enhance the binding affinities but also function as a gripper to seize the pore, making it easier to balance and stabilize the other component of the new derivatives. Although it is challenging to synthesize the compounds designed in silico, this study may perhaps serve as a trigger for additional anti-obesity research.Communicated by Ramaswamy H. Sarma.