Precision immunotherapy of CRC hinges on in-depth research and application of immunotherapy biomarkers. ICIs are highly effective in MSI-H CRC patients, yet this subgroup accounts for only approximately 5% of CRC cases, making it crucial to expand immunotherapy applicability. Recent studies have uncovered emerging biomarkers, such as TMB,
POLE/POLD1 mutations, epigenetic changes (e.g.,
ARID1A and
KMT2D), and DDR gene mutations, therefore presenting new treatment chances for MSS patients. Notably, MSS patients with a high TMB or
POLE/POLD1 mutations respond well to immunotherapy. Moreover, the CRC pathologic heterogeneity and complex immune microenvironment pose challenges. MeC, for example, has unique immune activation features, such as lymphocytic infiltration, elevated
IFN-γ pathway activity, increased MMR protein deficiency, and a 10%
POLE mutation rate, making MeC highly responsive to immunotherapy. This immune-active phenotype exhibits strong antitumor immunity and immunotherapeutic efficacy independent of MSI status (
Figure 1). Beyond focusing on the biomarkers’ guiding implications, the correlations with other elements in the TME should be studied. Whether biomarkers cooperate with cytokines, such as tumor necrosis factor-α, during the immune response
18 and interfere with the epithelial-mesenchymal transition
19 to affect tumor recurrence and metastasis should be determined. In addition, whether biomarkers can influence efficacy through associations with the gut microbiota and microbial metabolic profile should also be determined
20.