The origin of tumorigenesis and tumor development lies in the activation of abnormal pathways caused by disordered gene expression. The genes involved in these processes are collectively referred to as tumor-promoting genes or tumor suppressor genes. Abnormal activation of oncogenes or abnormal inactivation of tumor suppressor genes leads to abnormal activation or inhibition of intracellular pathways. These abnormal pathways eventually lead to abnormal cell proliferation, metastasis, and angiogenesis. At the same time, abnormal expression or dysfunctional pathways can also reshape the tumor microenvironment through abnormal behavior of tumor cells, creating a favorable environment for tumor cell proliferation and metastasis allowing the tumor to avoid immune-mediated tumor killing. These abnormally expressed genes, pathway disorders, and microenvironment abnormalities do not exist independently, they have complex interactions between them. This is not only the cause of tumor occurrence and development but also a potential target of treatment.

To fully discover the abnormal genes and pathways involved in cancer, an effective approach may be to detect cancer and adjacent normal tissue, however, this method is very challenging and resource-intensive. In the era of rapid development of statistical analysis, the study and treatment of tumors has also entered the digital age. The rapidly developing computer technology can be used to systematically analyze the existing global molecular map, calculate and extract abnormal gene expression, activated pathways, and changes in the tumor microenvironment, construct the visual process of tumor occurrence and development, and screen treatable targets. In addition, comprehensive analysis and comparison of different data sets may reduce the deviation caused by extracting samples from each data set. This can further increase the accuracy of analysis and provide more favorable treatment directions and treatment targets. The roles that abnormally expressed genes and disordered pathways play in tumorigenesis and development are extremely complex, particularly considering that the same genes may play opposing roles in different cancers or within different microenvironments. Bioinformatics analysis may describe the possible processes involved according to the correlation between genes or pathways, and preliminarily classify these into different groups. However, the specific mechanisms need to be further explored and confirmed by in vitro and in vivo experiments, which will provide more reliable data for precision treatment.

The purpose of this Special Issue is to collate original research and review articles to further understand the initial factors in tumor occurrence and development, construct the complex roles of genes, pathways, and tumor microenvironment, and to further discover new tumor biomarkers and therapeutic targets.

Potential topics include but are not limited to the following:

• Bioinformatics research based on new methods of cancer diagnosis, prognosis, and treatment
• Gene and pathway regulation mechanism of tumorigenesis
• Drug target discovery, targeted drug design, in vivo and in vitro validation of effect and mechanism
• Evaluation of immunotherapy and therapeutic strategies for regulating the immune response
• Epigenetics, metastasis, and immunometabolism