According to NCCN diagnosis and treatment guidelines, GC patients with pII/III stage should propose 5-Fu based chemotherapy[12].However, due to personal homogeneity, especially the difference in the metabolic microenvironment of somatic cells, some patients generally develop resistance to chemotherapy[13]. Recent studies have found that reprogramming of somatic metabolism plays a major role in the development trend of malignant tumors[14, 15]. Although most scientific research focuses on the role of single regulatory factors of FAM in GC[10], the overall efficacy of several FAM-related genes is unclear. Tumor cells show different metabolic characteristics from normal somatic cells[16]. This kind of connection may be related to the drug resistance of tumors to 5-FU treatment, but it has not been evaluated.
The results of the JCOG1104 trial[17] showed that for pII GC, the use of S-1 single-agent postoperative chemotherapy has better clinical benefit, which is consistent with the ACTS-GC trial results[18, 19]. According to the results of the JACCRO GC-07 trial[20, 21], multi-drug combination chemotherapy is recommended for pIII GC. Conventional regimens such as S-1 plus docetaxel or oxaliplatin combination regimen can be used[22]. However, due to individual heterogeneity, not everyone can benefit from this kind of chemotherapy regimen[23]. The choice of postoperative adjuvant chemotherapy should not only refer to pathological diagnosis, but also evaluate the patient's metabolism and drug resistance, so as to formulate the best individualized countermeasures.
In our research, 55 genetic genes related to FAM were selected and the number of hereditary genes was reduced. Totally, ten genetic genes were utilized to build a risk scoring model. Compared with the low-risk set, the survival time in the high-risk set was lower (all p < 0.001). The ROC of time-dependent subjects was carried out within 5 years to determine the accuracy of the risk scoring model (5 years, AUC = 0.793). Univariate and multivariate analysis verified the effectiveness of the model (all p < 0.001). Therefore, we have basically confirmed that this kind of FAM model can effectively distinguish the prognosis of patients. However, the ability of this model to individually assess 5-Fu treatment resistance is still unknown. To continue to explore the resistance to 5-Fu treatment, we first clustered patients into two distinct sub-types by NMF method. Subsequently, we further evaluated the chemo-sensitivity to 5-Fu, and it was found that the high-risk set was lower sensitive to 5-Fu chemotherapy. This may also partly explain this higher proportion of 5-Fu chemotherapy resistance in the high-risk group.
The relationship between FAM and immune microenvironment has been reported in the literature. It was found that the TIDE index of high-risk groups is higher, which indicates that high-risk groups may be more prone to immune escape. GSVA enrichment was conducted and it was found that most metabolism pathways, including FAM, got rich in the low-risk score. It was also found that in the high-risk group, the proportion of T cells follicular helper level was high, but the level of mast cells resting was low. According to the literature reports, the immune status of different subtypes may also lead to distinct sensitivity of immunotherapy. Frustratingly, we did not find any difference in immune binding sites (PD-L1 and CTLA4) and TMB. This may indicate that pII-III GC does not benefits from immunotherapy. However, these results need to be verified by future large sample, multi center clinical studies.
In order to evaluate the effectiveness of the FAM model independently, we integrated the metabolic model and clinical characteristics into the analysis. Firstly, a sankey diagram integrating age, gender, pathological TNM staging and post-treatment risk score was proposed, and a nomograph model was built. We can confirm that the low-risk score of FAM model is close to 10 points, but the score of the high-risk group is increased to about 55 points. Therefore, the prognosis of patients can be independently evaluated by this model.
The limitations of our research include : firstly, this study is based on publicly available data, some important clinicopathological features cannot be analyzed, which may lead to potential errors or bias. Secondly, the GPL6947 platform includes only a small portion of all possible mRNA, which may not represent a complete mRNA population of GC biological behavior.
In conclusion, the fatty acid prognostic risk score model can comprehensively evaluate the clinical characteristics of stage II-III GC. In addition, The model believes that owners of low-risk groups have better 5-Fu drug sensitivity, lower probability of immune escape, and better prognosis.