Silencing the Peptide Transporter TAP Forces Tumors to Display New Antigens the Immune System Can Attack | Research

The takeaway

Tumor-targeted TAP silencing via siRNA forced cancer cells to present a new set of peptides that triggered potent anti-tumor immunity across multiple mouse tumor models, enhancing the effectiveness of PD-1 blockade.

Creates new tumor antigens
Silencing TAP forces tumors to present an entirely different peptide repertoire — converting immunotherapy-resistant 'cold' tumors into targetable 'hot' tumors

What the researchers found

Silencing the peptide transporter TAP in tumor cells forced them to present a new set of peptide antigens that the immune system could recognize and attack. Tumor-targeted delivery of TAP siRNA via a nucleolin aptamer inhibited tumor growth across multiple tumor models without measurable toxicity. The approach was comparably effective to vaccination against mutation-generated neoantigens, potentiated the effects of PD-1 antibody and Flt3 ligand, and induced TAP-independent peptide presentation in human tumor cells.

Why it matters

Most cancer immunotherapy works best when tumors have many neoantigens (mutations the immune system can target). But many cancers have few neoantigens, making them resistant to checkpoint inhibitors. This study introduces a creative workaround: instead of finding existing neoantigens, force tumors to create new ones by blocking their peptide processing machinery. By shutting down TAP, the tumor cell surface displays an entirely different set of peptides that the immune system treats as foreign. This could make immunotherapy-resistant 'cold' tumors into targetable 'hot' tumors.

The numbers in context

Multiple tumor models · Nucleolin aptamer-TAP siRNA conjugate · No measurable toxicity · Comparable to neoantigen vaccination · Potentiated PD-1 + Flt3L · Human tumor cell validation · Published in Nature Communications

How the study worked

Chemically synthesized nucleolin aptamer (targeting tumors) was conjugated to TAP-targeting siRNA. The conjugate was administered systemically in mice bearing various tumor types. Tumor growth, immune responses, and toxicity were assessed. Combination experiments tested TAP silencing with PD-1 antibody and Flt3 ligand. Human tumor cells were tested for TAP-independent peptide presentation in vitro.

What this study cannot tell us

Preclinical mouse study — human tumors in vivo may respond differently. TAP silencing is transient (siRNA effect), so repeated dosing would be needed. The nucleolin aptamer targets broadly rather than tumor-specifically, though toxicity was minimal. Whether the TAP-independent peptide repertoire is sufficiently immunogenic in humans with their diverse HLA types needs clinical testing.

How to read the evidence

High-quality preclinical study published in Nature Communications using multiple tumor models, combination therapy experiments, and human tumor cell validation. The breadth of evidence (multiple models, combination effects, no toxicity) is impressive but remains preclinical.

When this study was published

Published in 2019, this study introduced a novel immunotherapy strategy. The concept of modifying tumor antigen presentation to enhance immunotherapy continues to be explored in subsequent research.

The bigger picture

This study tackles one of immunotherapy's biggest unsolved problems: how to treat 'cold' tumors that lack neoantigens. Rather than searching for existing mutations (the neoantigen vaccine approach), this strategy creates new targetable peptides by disrupting the cell's antigen processing machinery. It's an elegant concept — instead of finding the needle in the haystack, change what the haystack is made of. Published in Nature Communications, it represents a paradigm shift in cancer immunotherapy strategy that could expand checkpoint inhibitor therapy to the majority of patients who currently don't respond.

Questions still open

Could TAP silencing be combined with personalized neoantigen vaccines for a dual-antigen attack on tumors?
Will the TAP-independent peptides presented in human tumors be recognized by patients' immune systems across diverse HLA types?
How frequently would TAP siRNA need to be re-administered to maintain the altered peptide display?

Common questions

How does silencing TAP make tumors visible to the immune system?

TAP is a transporter that loads normal peptide fragments onto MHC-I molecules on the cell surface. When TAP is silenced, the cell can't load its normal peptides, so it displays an unusual set of TAP-independent peptides instead. The immune system recognizes these abnormal peptides as foreign — like a criminal wearing someone else's clothes — and attacks the tumor cells.

Could this work for cancers that don't respond to immunotherapy?

That's exactly the point. Many cancers resist immunotherapy because they have too few neoantigens for the immune system to target. This approach doesn't rely on existing mutations — it creates new targetable peptides by disrupting the tumor's peptide processing. In mice, it worked across multiple tumor types and enhanced the effect of PD-1 checkpoint blockade, suggesting it could help expand immunotherapy to currently unresponsive cancers.

Read the original research

Tumor-targeted silencing of the peptide transporter TAP induces potent antitumor immunity.

Nature communications, 10(1), 3773

View on PubMed ↗Publisher’s paper ↗

Citation

Garrido, Greta; Schrand, Brett; Rabasa, Ailem; Levay, Agata; D'Eramo, Francesca; Berezhnoy, Alexey; Modi, Shrey; Gefen, Tal; Marijt, Koen; Doorduijn, Elien; Dudeja, Vikas; van Hall, Thorbald; Gilboa, Eli. (2019). Tumor-targeted silencing of the peptide transporter TAP induces potent antitumor immunity.. Nature communications, 10(1), 3773. https://doi.org/10.1038/s41467-019-11728-2