According to the latest data from GLOBOCAN, cervical cancer, as the fourth most common malignant tumor in women worldwide, was the first tumor to develop in women in 23 countries and the first cause of death in women in 36 countries in 2020[23]. It is a serious threat to women's health. The main treatment modalities for cervical cancer include surgery, radiotherapy and chemotherapy, but patients with advanced, recurrent and metastatic cervical cancer lack effective treatment, with a 5-year survival rate of 16.8%. With the application of anti-angiogenesis inhibitors, the efficacy of advanced cervical cancer has improved, for example, bevacizumab combined with chemotherapy can significantly improve the overall survival of patients with advanced cervical cancer, but the overall treatment effect is still unsatisfactory, and the median survival of advanced cervical cancer is only 16.8 months[24, 25]. The development of immunotherapy recently has made immune checkpoint inhibitors (ICI) unsurprisingly a highly anticipated potential treatment for cervical cancer by researchers[26]. The well-known KEYNOTE-158 and CheckMate 358 studies have demonstrated the efficacy of pembrolizumab and nivolumab in advanced cervical cancer, increasing ORR and improving overall survival to some extent[27]. Notably, with pembrolizumab, PD-L1 was shown to be a potential marker for predicting response, but positive PD-L1 expression does not necessarily mean that pembrolizumab is effective, and for nivolumab, positive PD-L1 expression did not serve as a predictor of efficacy (10–11). This finding reflects the heterogeneity of tumors and the complexity of the immune system-tumor interaction and suggests that how to effectively characterize the immune microenvironment of cervical cancer patients and identify new molecular markers to screen the population for the benefit of immunotherapy becomes the first issue to be addressed.
Cancer can be considered a metabolic disorder[28]. In order to obtain nutrients for malignant cell growth and proliferation, metabolic reprogramming, which interferes with normal metabolic activities through various pathways mediated by oncogenes and oncogenes, has become one of the important hallmarks of cancer, in which disorders of lipid metabolism lead to abnormal gene expression and dysregulation of signaling pathways, and play an important role in the development of cancer, as an important component of lipid metabolism[9]. Fatty acid metabolic reprogramming plays an important role in the malignant transformation of many cancers and is involved in several pathophysiological processes of cancer progression, including biofilm synthesis, signal transduction, neovascularization, and invasion and metastasis[29]. Several studies have shown that the upregulation of fatty acid synthase and increased fatty acid synthesis in various cancers are associated with poor prognosis[30]. In addition, fatty acid metabolism has an important role in the development, differentiation, function, and distribution of different T cell subsets, and can also alter tumor immunity by recruiting immune cells to the tumor microenvironment[31]. However, the mechanism of fatty acid metabolism reprogramming in CESC is not yet understood. This study aims to develop a prognostic model related to fatty acid metabolism genes and to investigate the relationship between fatty acid metabolism genes and immunotherapy in cervical cancer.
With the development of high-throughput sequencing technology and bioinformatics analysis, attempts have been made to molecularly type tumors based on key features, which have been used to achieve optimal patient stratification and precise treatment. In view of the close relationship between fatty acid metabolism and tumor development, this study utilized fatty acid metabolism-related genes for molecular typing of CESC and explored the potential clinical applications. We classified CESC into 3 subtypes by NMF non-negative matrix clustering based on 174 fatty acid metabolism genes, and survival analysis showed that the C3 type had the best prognosis and the C1 type had the worst prognosis. To understand the potential reasons for this prognostic difference, we performed the analysis of immune cell infiltration in the tumor microenvironment for each of the 3 subtypes and performed gene set variation analysis for C1 and C3 types (GSVA) and gene-set enrichment analysis (KEGG). The results showed a higher abundance of infiltrating B lymphocytes and myeloid dendritic cells in the C3 subtype with a better prognosis. Dendritic cells are the most powerful specialized antigen-presenting cells in the body, which can efficiently uptake, process, and present antigens, and are closely related to tumorigenesis and progression, and the number of infiltrating DCs in most solid tumors is positively correlated with prognosis. cells to regulate the immune response to promote cellular immunity[32]. A growing number of studies suggest that B cells play a role in antitumor immunity and may benefit patient prognosis. Therefore, the higher abundance of immune cell infiltration may be the main reason for the good prognosis of type C3(33). In contrast, type C1 becomes enriched in fibroblasts. And fibroblasts, as the main mesenchymal cells in the tumor microenvironment, can increase the invasive and metastatic ability of tumor cells, which is closely related to tumor malignancy, progression, and poor prognosis[34]. C1 type is mainly enriched in ECM RECEPTOR INTERACTION, adhesion junctions, and adhesion spot pathways, which are closely related to cancer invasion and metastasis[35]. Adherent spots are composite structures at the cell-ECM junction, directing multiple changes in gene expression and cytoskeletal reorganization, and also recruiting multiple functional proteins to participate in the regulation of different signaling pathways, affecting cell migration, invasion and metastasis. We, therefore, hypothesized that the poorer prognosis of type C1 is associated with high infiltration of fibroblasts and enrichment of adhesion-linkage-related pathways.
We performed weighted gene co-expression network analysis (i.e., WGCNA) by hierarchical clustering to screen out Blue modules with good correlation to C3 type, and took intersections with differential genes to obtain a total of 25 intersecting genes. Based on these 25 intersecting genes, six FARGs (fat acid-related genes), namely PTPN12, PLOD2, ASPH, ACLY, PGM and AMFK, were screened using the least absolute contraction and selection operator LASSO regression. except for PTPN12 as a tumor suppressor, the remaining five FARGs played a tumor-promoting role in most cancer species PTPN12 is a member of the protein tyrosine phosphatase (PTP) family and acts as a tumor suppressor to inhibit tumor cell growth, migration and invasion in a variety of cancers such as liver, bladder and renal cell carcinomas[36]. PLOD2 is a member of the PLOD family (PLOD1, PLOD2, PLOD3) and encodes a specific protein that mediates[37]. ASPH is highly expressed in more than 20 solid tumors such as cervical cancer, liver cancer, bile duct cancer and gastric cancer with a malignant phenotype, and is associated with increased cell proliferation, invasion and metastasis, as well as poor prognosis[38]. ACLY is usually upregulated or activated in cancer cells to accelerate lipid synthesis and promote tumor progression, including non-small cell lung, colorectal, renal, epithelial ovarian, prostate, breast, bladder, hepatocellular and ovarian cancers, and often represents a poor prognosis[39]. PGM1 gene encodes phosphoglucose translocase 1, an important component of metabolic conversion, which is highly expressed to promote cancer progression and is associated with poor prognosis. in breast cancer where MAFK induces EMT to promote invasive tumor formation. Therefore, we hypothesized that these fatty acid metabolism-related genes play a role in promoting tumor progression in CESC and could be used as potential therapeutic targets to provide new ideas and directions for the treatment of CESC[40].
We used six FARGs to construct a risk-prognosis model of CESC with fatty acid metabolism characteristics, and divided patients into high- and low-risk groups for survival analysis based on risk scores, and the results of ROC curves showed the predictive accuracy of the model. The results of ROC curves and DCA curves further confirmed the excellent predictive performance of the model. The results of ROC curves and DCA curves further confirmed the excellent predictive performance of the model, indicating that the model we constructed can guide clinicians to assess patient survival more accurately and effectively compared to TNM staging alone. There was also a close relationship between risk score and tumor immune microenvironment in CESC, with a relatively higher immune score in the low-risk group, and this result was also consistent with the subsequent analysis of immune cell infiltration abundance, where CD8+ T-cells were more abundant in the low-risk group than in the high-risk group[41]. Tumor-infiltrating CD8+ T-cells are the key lymphocytes responsible for tumor killing in tumor immunity, and high infiltration levels of CD8+ T-cells improve response to chemotherapy and immunotherapy in most solid tumors and are considered to be a marker of good prognosis. The IPS-PD1 blocker score, IPS-CTLA4 score and PD1 blocker score were significantly higher in the low-risk group than in the high-risk group, and the Immunophenoscore (IPS) quantifies the determinants of tumor immunogenicity, with higher scores implying better immunotherapy outcomes. Based on the results of the IPS score and immune cell infiltration abundance analysis, we concluded that patients in the low-risk group were more likely to benefit from immunotherapy and also confirmed that the risk score could be a reliable predictor of immunotherapy efficacy in CESC patients.
The results of the GSEA analysis further reveal the potential mechanism of action of a risk score to influence the prognosis of CESC patients. Both in the KEGG dataset and the HALLMARK dataset, the high-risk cohort was enriched in pathways related to tumorigenesis development, thus leading to poorer patient prognosis. For example, Epithelial-mesenchymal transition (EMT) is an important biological process by which tumor cells acquire the ability to migrate and invade. activation of the IL-6/JAK/STAT3 pathway drives malignant transformation and proliferation of tumor cells, inhibits apoptosis, promotes invasive metastasis, and suppresses tumor immune response[42]. In contrast, angiogenesis is a critical and early step in tumorigenesis, a hallmark of solid tumors, and a key promoter of tumor recurrence. The low-risk group is mainly enriched in DNA damage-repair-related pathways, including mismatch repair, homologous recombination, and non-homologous end-joining. Accurate DNA damage response and repair are essential to maintain the integrity of the normal cellular genome, and functional loss of its key genes can promote tumorigenesis and progression[43]. We, therefore, hypothesize that the low-risk group is enriched in DNA damage repair, a critical pathway for maintaining genomic stability, as the main reason for the good prognosis of patients.