With an estimated prevalence exceeding 1 million cases by the year 2025, LIHC presents a significant threat to human well-being owing to its elevated occurrence and fatality rate. The primary risk factors associated with the development of liver cancer, namely LIHC, encompass infections caused by the hepatitis B and C viruses23. The management of LIHC continues to provide significant challenges, mostly relying on the timely identification of the disease. AFP is presently the prevailing biomarker employed for the early detection of liver cancer24. The expression of AFP is elevated in certain individuals diagnosed with hepatitis, germ cell tumors, and gastric cancer 25–27. Hence, it is of utmost significance to ascertain biomarkers that can monitor LIHC.
The CRLF3 gene encodes the protein known as cytokine receptor-like factor 3 in humans. Phylogenetic investigations have provided evidence indicating that the emergence of CRLF3 can be traced back to a shared ancestor of Cnidaria and Bilateria, coinciding with the genesis of the nervous system28,29. The protein CRLF3 is highly conserved throughout metazoans and possesses a characteristic cytokine receptor homology domain (CHD). CRLF3 is known to have significant involvement in numerous developmental and homeostatic mechanisms, with a particular emphasis on blood and immune cell functions. Moreover, prior research has provided evidence indicating that CRLF3 plays a crucial role in the start of hematopoiesis in the early embryonic phases of zebrafish18. The dysregulation of CRLF3 expression has been observed in cutaneous squamous cell carcinoma, thereby enhancing our comprehension of the etiology and advancement of this condition, as well as diagnostic approaches30. The prognostic importance of CRLF3 in LIHC has not yet been thoroughly investigated in the current literature. Therefore, the main aim of this work is to examine the prognostic importance of CRLF3 expression in liver hepatocellular carcinoma (LIHC) and understand the underlying regulatory mechanisms involved.
Initially, an examination was conducted on the expression levels of the CRLF3 family. It was observed that the members of the CRLF3 family had a significantly elevated expression level in comparison to that of normal tissues. Univariate and multivariate Cox regression studies were conducted on members of the CRLF family with OS. CRLF3 was included in the study based on the obtained results. Following this, a study was undertaken to analyze the mRNA and protein expression levels of CRLF3 in both liver hepatocellular carcinoma (LIHC) tissues and normal tissues. The results of a Kaplan-Meier analysis revealed that individuals with liver LIHC who exhibited elevated expression levels of CRLF3 experienced a poorer prognosis. In addition, the findings of a multivariate Cox regression analysis revealed that elevated expression of CRLF3 was identified as an autonomous risk factor linked to reduced OS among patients diagnosed with LIHC. The receiver operating characteristic (ROC) analysis demonstrated that CRLF3 exhibits a substantial diagnostic utility.
To further our comprehension of the molecular process underlying CRLF3, we conducted an analysis aimed at identifying the genes that interact with CRLF3 and exhibit differential expression (referred to as DEG genes). Based on our research, it can be inferred that there exists a close association between CRLF3 and ATAD5. ATAD5, the human counterpart of the yeast protein Elg1, is involved in the process of PCNA deubiquitination31. Genetic and functional defects in ATAD5 contribute to cancer susceptibility in mammals32, and ATAD5 plays a very important role in different DNA repairs33. ATAD5, the human counterpart of the yeast protein Elg1, is involved in the process of PCNA deubiquitination34. Therefore, it is plausible that ATAD5 could potentially exert a pivotal regulatory function in the progression of LIHC.
The GSEA analysis revealed that CRLF3 has a role in various cellular processes, including PI3K Akt, Wnt, FcεRI-mediated NF-κB activation, activation of the intestinal immune network for IgA synthesis, interactions between immune cells and microRNAs in the tumor microenvironment, and JAK/STAT signaling pathways. The dysregulation of the PI3K/AKT/mTOR signaling pathway is a prevalent occurrence in LIHC. The protein in question assumes a regulatory function in the metabolic processes of glucose, lipids, amino acids, pyrimidines, and oxidative reactions in the liver 35,36. The Wnt signaling pathway is of significant importance in the processes of cell fate determination, proliferation, and the formation of cell polarity37. The disruption of the WNT/β-catenin signaling pathway has been observed in the development of LIHC, suggesting its substantial regulatory involvement in the pathogenesis of this specific malignancy38. The signaling system responsible for NF-κB activation through FcεRI can effectively regulate the immune-inflammatory response, hence exerting a significant influence on the advancement of cancer39. Interactions between immune cells and microRNAs in the tumor microenvironment signaling pathway have a role in various biological processes of tumor development, such as proliferation, invasion, and evasion. These interactions can either promote or suppress tumor progression40. Research has demonstrated that the initiation and advancement of certain diseases, such as inflammatory disorders, lymphomas, leukemias, and solid tumors, are facilitated by the activation of the JAK/STAT pathway41,42. The findings of this research suggest that CRLF3 possesses the capacity to regulate the progression of cancer through its influence on many signaling pathways.
The tumor microenvironment (TME) encompasses the milieu encompassing the tumor, comprising adjacent blood vessels, immune system components, and immune cells. 43. According to a recent mechanistic study, it has been proposed that immune cells can exert either anti-tumor or pro-tumor effects through the secretion of various cytokines, chemokines, and other substances. These factors play a crucial role in determining the initiation and progression of tumors44. In recent years, several studies have provided insights into the substantial role played by immune cell infiltration in the progression of liver carcinogenesis, and its potential implications for the prognostication and treatment of LIHC45,46. Following that, the ssGSEA technique was employed to measure the amounts of infiltration of 24 specific immune cell types within the tumor microenvironment of LIHC. Our research revealed a strong correlation between CRLF3 and T helper and Th2 cells. Moreover, increased circulating Th2 cells are associated with a more advanced tumor stage and poorer treatment response47,48. The aforementioned research indicates that CRLF3 is involved in the advancement of LIHC through its regulation of immune cell infiltration inside the tumor microenvironment.
In conclusion, our research indicates that CRLF3 potentially serves as a mediator in the diagnosis, prognosis, and survival of LIHC. The progression of LIHC is influenced by CRLF3 through many signaling pathways, including PI3K Akt, Wnt, FcεRI-mediated NF-κB activation, activation of the intestinal immunity network for IgA synthesis, interactions between immune cells and microRNAs, and JAK/STAT signaling pathways within the tumor microenvironment. Moreover, it is plausible that CRLF3 may have a significant impact on the modulation of T helper cells. Undoubtedly, this paper exhibits numerous shortcomings. We have only validated the expression levels of CRLF3 in tumour tissues and paracancerous normal tissues, and the lack of experimental validation limits our understanding of the underlying molecular mechanisms. Therefore, further data collection and in-depth investigations are required to address this matter. In summary, our findings offer a solid foundation for further investigations into the mechanistic cascade of CRLF3 in the progression of LIHC.