Dana-Farber study reveals how half of cancers hide from immune cells

Cancers carrying mutations in the p53 tumor-suppressor protein — found in roughly half of all human malignancies — can effectively conceal those mutations from the immune cells meant to destroy them, according to new research from Dana-Farber Cancer Institute published this week in the journal Immunity.newswise+1

The study, led by scientists including first author Koji Haratani and co-supervising authors Ellis L. Reinherz and David A. Barbie, proposes a counterstrategy the researchers call an "immunopeptidome shift": using drugs to alter what a cancer cell displays on its surface, potentially converting immunologically "cold" tumors into ones the immune system can attack.sciencedirect+1

The Visibility Problem

T cells do not read a tumor's DNA directly. Instead, they scan tiny protein fragments, or peptides, held on the cell surface by HLA molecules. The full collection of these fragments — the immunopeptidome — functions as a molecular window display. If a cancer-specific fragment never reaches that window, even a capable T cell has nothing to target.sciencedirect+1

Using ultrasensitive mass spectrometry, the investigators found that p53 is far less visible to T cells than genomic sequencing or computational predictions would suggest. Of 175 predicted wild-type p53 peptide candidates examined, only five were robustly detected on tumor cell surfaces. Many common cancer-causing p53 "hotspot" mutations fell in regions that were poorly processed and failed to generate any detectable surface targets.newswise+1

The team identified several additional escape routes. In one case, an enzyme called ERAP1 destroyed an otherwise immunogenic p53 fragment before it could be displayed. Deleting or inhibiting ERAP1 restored T-cell recognition in laboratory experiments. In another, the common p53 R175H mutation produced a peptide that bound its HLA molecule so weakly the complex was unstable and short-lived, undermining T-cell killing despite the presence of highly sensitive T-cell receptors.dana-farber+1

From Stronger T Cells to Better Targets

Most current immunotherapies focus on strengthening the immune response — checkpoint inhibitors release molecular brakes on T cells, while engineered therapies supply large numbers of active immune cells. This study argues the other side of the equation may be equally important: making the cancer display better targets in the first place.newswise+1

The proposed immunopeptidome shift strategy includes ERAP1 inhibitors, small molecules that alter which peptides fit into HLA molecules, and drugs that change RNA splicing. If delivered selectively to tumors, such agents could expose multiple new targets simultaneously, making immune escape harder than it is against single-target therapies.sciencedirect+1

Implications for Cold Tumors

The approach is particularly relevant to pancreatic, prostate, ovarian, and brain cancers, as well as immunologically cold forms of breast cancer — tumor types that have largely resisted checkpoint immunotherapy. The researchers envision combining immunopeptidome-shifting drugs with checkpoint inhibitors, therapeutic vaccines, or engineered T-cell therapies rather than replacing them.oncodaily+1

"Immunotherapy cannot attack what the immune system cannot see," Reinherz said. "If we can pharmacologically change the peptides a cancer displays, we may be able to create the targets that endogenous T cells, checkpoint therapies and engineered T cells need to work."newswise