CDK4 and cervical squamous intraepithelial neoplasia: It is conceivable and even probable that only specific sub-types of each primary gastrointestinal cancer would be innately sensitive to CDK4/6 inhibition, while others would be more resistant, as suggested by the example of MSI- and EBV-related gastric cancers versus CIN and genomically stable gastric cancers, discussed in a previous section.