Core Framework & Diagram How Do Cancer Cells Evade the Immune System? 2

PD-1 inhibitors require T cells to already be present in the tumor to work ('hot tumor'). If the tumor has essentially no T cell infiltration ('cold tumor'), releasing PD-1 blockade has no T cells to liberate. Cold tumor treatment needs to first recruit T cells (via radiation, chemotherapy, or vaccines), then use checkpoint inhibitors. This is why 'hot/cold tumor' classification is so important clinically.

For tumors with low (or absent) MHC-I expression, NK cell therapy theoretically has advantages because NK cells don't need MHC-I to recognize target cells. Blood tumors (leukemia, lymphoma) are the fastest-progressing clinical area for NK cell therapy; solid tumors face greater challenges from tumor microenvironment barriers, but research is advancing rapidly.

Immunotherapy resistance is one of the most important clinical challenges. Resistance mechanisms include: loss of tumor antigens (evolutionary escape), upregulation of new immune checkpoints (TIGIT, TIM-3, LAG-3), and tumor microenvironment remodeling. Countermeasures are combination treatments: simultaneously targeting multiple checkpoints, combining different immunotherapy mechanisms, or combining with radiation/chemotherapy to re-activate the immunity cycle.

In a sense, yes. Chronic inflammatory environments drive immune cells toward M2/Treg polarization — exactly the suppressive microenvironment tumors need. This is why chronic inflammation (like chronic hepatitis, chronic colitis) significantly increases specific cancer risks — not only because inflammation drives cellular mutations but also because inflammation creates immune environments favorable to tumor evasion.

Currently, for ordinary high-risk populations, standard tumor screening (colonoscopy, mammography, low-dose CT, etc.) is recommended, not 'immune testing.' The most evidence-supported preventive measures remain: regular exercise, adequate sleep, not smoking, maintaining healthy body weight — all of which through real immune mechanisms reduce tumor evasion opportunities.