Pain is the most common symptom in cancer patients referred to palliative care[27]. The total number of cancer patients/survivors is forecast to exceed 20 million by 2026[28]. The number of people suffering from cancer pain will also keep on increasing. Pain can affect social relationships with family and caregivers, and concerns about pain are the second most common problem reported by relatives caring for someone with advanced cancer at home[29]. Pain is a major problem for people with colon adenocarcinoma and does not improve with time. Stoma procedures are typical for these sufferers and may cause a unique experience of pain, worry, and disconnect from ordinary activities[30]. Patients with colon adenocarcinoma who have chronic pain are more likely to report psychological distress in the years following therapy[31, 32]. Furthermore, many studies have shown that people with painful colon adenocarcinoma are more likely to suffer from negative emotions such as anxiety and depression than those without pain[33, 34]. Adverse symptoms such as pain can be very burdensome for patients with colon adenocarcinoma and can have a very negative impact on the overall health-related quality of life (QoL) of patients with colon cancer[35]. Pain-related genes play an important role in the prognosis and pain-related effects of cancer patients, and low-expression of pain-related genes improves the survival of cancer patients[23]. This study is a correlation analysis of pain subtypes in COAD to suggest some solutions for COAD treatment.
We obtained and validated four pain subtypes (CS1, CS2, CS3, CS4) and four stable subtypes (CMS1, CMS2, CMS3, CMS4) by pathway analysis of pain gene enrichment associated with colon adenocarcinoma. By comparing the pain subtypes with the classical subtypes, we found that CS1 was more associated with CMS4, and CS3 was more associated with CMS2. The marker genes for these subtypes, which we subsequently selected by the PAM algorithm, were also validated in the TCGA and GEO datasets; however, the analysis of survival differences performed between the four pain subtypes was not statistically significant. Yet, CS1 had a poorer prognosis compared to the performance of several other subtypes.
We then analyzed the enrichment pathways of marker genes for each subtype. The marker genes of CS1 were mainly enriched in pathways such as Focal adhesion, Focal adhesion affects almost all aspects of cellular life[36], of which the integrin family is a central part[37]. Integrin heterodimers can trigger signalling in cancer, and the behaviour of cancer cells is determined by integrin expression patterns[38]. Once integrins are activated, downstream cascades, including the PI3K/AKT and MAPK pathways, are initiated to promote tumour survival and progression. Integrins are present in tumour cells and tumour-associated host cells and profoundly affect the tumour cells and the tumour microenvironment[39]. Integrin α3 and β3 transcription and focal adhesion signalling are required for colorectal cancer growth and migration[40]. The marker genes of CS2 were mainly enriched in pathways such as Human T cell leukemia virus1(HTLV-1)infection, HTLV-1-infected cells contribute to the freedom of infected cells from host immunosurveillance, inducing T cells to develop anergy and immunosuppressive functions[41]. And the marker genes of CS3 were mainly enriched in pathways such as the Metabolic pathway. The marker genes of CS4 were mainly enriched in pathways such as Pertussis. The study of these enrichment pathways has led to a better understanding of the different subtypes of marker genes.
Over time, it has been recognized that cancer is an evolutionary and ecological process associated with continuous, dynamic, and interactive interaction between cancer cells and the tumour microenvironment (TME)[42]. The TME includes all noncancerous host cells in the tumour, such as the fibroblasts, endothelium, neurons, adipocytes, adaptive and innate immune cells, as well as their noncellular components, including the extracellular matrix (ECM), and soluble products such as chemokines, cytokines, growth factors, and extracellular vesicles[43]. Targeting TME offers significant therapeutic advantages over direct targeting of cancer cells, which are susceptible to drug resistance due to their genomic instability. In contrast, non-tumour cells in TME are genetically more stable and vulnerable[43]. Next, we analyzed the differences in the TME between the different subtypes. We showed that CS1 and CS4 had higher expression of immune checkpoints and immune cell infiltration, as well as higher ImmuneScore and StromalScore, indicating that there were more immune or matrix components in the TME, so CS1 and CS4 were more immunogenic. This provides new ideas for us to treat different subtypes of colon adenocarcinoma.
Recently, immune checkpoint molecules such as PD-1 have been identified as targets for immunotherapy in colon adenocarcinoma[44]. Human colon cancer cells express functional PD-1, and it also blocks the growth of human colon cancer cells[45]. CTLA-4 has been correlated with persistent clinical responses against a diverse range of cancer types has excellent potential as a novel cancer treatment [46–48], and is the first to be approved for cancer treatment[49]. Finally, the sensitivity of different subtypes to immunotherapy and chemotherapy was analyzed, with CS4 being more sensitive to PD-1 inhibitors and CS1 being more sensitive to CTLA-4 inhibitors, and the four subtypes differing in their sensitivity to common chemotherapeutic agents such as Bexarotene, Bortezomib, Camptothecin, Cytarabine, Cisplatin, Cytarabine, Docetaxel, Gefitinib, Methotrexate, and Temsirolimus. Cisplatin, Cytarabine, Docetaxel, Gefitinib, Methotrexate, Temsirolimus, and other common chemotherapeutic agents, with CS4 showing lower IC50 values for these chemotherapeutic agents, indicating that CS4 is more sensitive to these chemotherapies. These results provide new findings for the immunotherapy of COAD as well as chemotherapy.
This article relies on publicly available databases for data collection, and while these databases are widely used and provide a valuable resource, they have inherent limitations, including potentially inconsistent, biased, and incomplete data. Clinical validation and further experimental evidence to support these findings would be beneficial. Also, gene sets and datasets are not large enough to draw broad conclusions or generalize findings to the entire population. The limited sample size may limit the statistical efficacy and significance of the results.