In 2016, the American Society of Clinical Oncology (ASCO) named immunotherapy the “Advance of the Year”. Within a few years, it has revolutionized cancer therapy. Therefore, there is an increasing need to identify novel potential biomarkers for the complex responses of immune checkpoint inhibitors, which would further increase the treatment responses and prolong the survival of cancer patients. Biomarkers are biological/pathological molecules present in or produced by patients, which could be found in blood, tumor cells, or tissue at the genomic, cellular, and soluble levels. Such biomarkers come in different forms, for example, host genomic factors, serum proteins, and nucleic acids (DNA or RNA molecules) within tumor cells and their microenvironments. Ideal biomarkers could aid healthcare professionals to achieve optimal treatment goals and bring clinical benefits to patients.

In the past decade, multiple tumor biomarkers have been validated and are widely used in clinics with proven effectiveness. However, there is still a need to develop new strategies to improve the efficiency and accuracy of cancer treatments by identifying more reliable biomarkers. With the development of high-throughput sequencing technologies in proteomics and genomics, both single and multifactorial synergistic markers have been gradually explored for clinical purposes using a variety of biomarker strategies. For instance, mass spectrometry improved the diagnosis of hybrid tumors and bulk, as well as single-cell sequencing which improved our current understanding of tumor cell-specific markers used for early diagnosis. Identification of multiple immune-checkpoint markers that are critical for developing therapeutic targets for precise immune-oncology, would have a profound impact in the field of personalized medicine.

The aim of this Special Issue is to bring together original research and review articles focusing on exploring novel predictive biomarkers for cancer diagnosis and prognosis, with an emphasis on immunotherapy techniques.

Potential topics include but are not limited to the following:

• Tumor genome and neoantigen-related biomarkers
• Tumor immune microenvironment phenotype-associated biomarkers
• Liquid biopsy biomarkers such as circulating tumor DNA or peripheral blood cell biomarkers
• Biomarkers for tumor diagnosis and immunotherapy targets
• Use of biomarkers for the assessment of prognosis of tumors
• Biomarkers for predicting tumor recurrence and metastasis
• Biomarkers for identification of tumor-associated cell types
• The spatial-temporal changes and regulatory mechanisms involved with biomarkers
• New methodologies including algorithms used for characterization of tumor biomarkers