Oral Nano-Delivery of a Gut Microbial Metabolite Enhances T Cell Stemness for Cancer Immunotherapy
August 2026, Nature Nanotechnology. Authors included Kai Han, Young Seok Cho, and two dozen other researchers.
Table of Contents:
The Overview
A joint research team has developed the world’s first oral, microbiome-based nanomedicine. They tested several metabolites produced by gut microbes and identified DHB, dihydroxybenzoic acid, as being capable of improving PD-1 cancer immunotherapy by reducing T cell exhaustion and promoting the formation of memory T cells. However, oral ingestion was ineffective in augmenting treatment, so they enclosed it in a protective shell that allowed it to reach the cancer targets, reduce T cell exhaustion, and enhance activity.
The Study
Researchers at the University of Michigan have found a compound produced in the intestine to potentially offer a way to improve cancer immunotherapy.
In a study using mice, the compound, called 3,4-dihydroxybenzoic acid (DHB), was produced when dietary fiber is broken down by bacteria. The researchers were able to turn this metabolite into an oral drug that allowed T cells to multiply rapidly and develop into memory T cells that improve anti-tumor responses and attack tumors more effectively.
How PD-1 Normally Works
In the body, active immune T cells (CD4 and CD8 T cells, regulatory T cells, and some NK, or natural killer, cells and B cells) are designed to identify foreign antigens and then become strongly activated when recognized. This occurs when the antigen-presenting cells (APCs), which carry the PD-L1 and PD-L2 proteins, transport antigens for binding to the T cell’s PD-1, or programmed cell death protein 1, receptor for activation. This combination of PD-1 and PD-L1 interconnection activates T cells but also acts to balance the intensity of the T cell response, modulating the level of immune activation to prevent an overactive, aggressive response.
In cancer, tumors can create an environment with PD-L1 proteins, either on their cell surface directly or in the surrounding tumor microenvironment (TME). Under normal circumstances when the T cell is activated, in cancer, it readily attacks the tumor. But these tumor-related PD-L1 receptors bind to the T cell PD-1 receptors and act to restrict or dampen immune response, providing the tumor with a way to turn on the T cell braking system.
Why Immunotherapy Often Falls Short
In cancer treatment, the relatively new immunotherapy, the PD-1 inhibitors, are designed to take the brakes off the immune system and allow it to attack the tumor cells more aggressively. They are not universally effective in all cancers, and many people do not respond. Even in people that do respond, a common mechanism of failure, according to the researchers, is that the T cells slowly lose the ability to kill cancer cells, because cancer produces high lactate levels in their production of energy, called glycolysis, which exhausts T cell function and diminishes activity. The researchers were therefore looking for compounds to reduce this decline and discovered DHB.
They found that DHB blocks this metabolic exhaustion and promotes T cell survival and activity, which allows their ability to continue attacking cancer cells.
Making DHB Work as an Oral Drug
One impediment to using DHB was that it was poorly absorbed and eliminated quickly from the body. So they created an inactive form of DHB, covered it in a protective nanoemulsion shell which upon reaching its target then became activated, and boosted its bioavailability by 14.3 times.
What the Researchers Found
In their study, using a mouse model of melanoma, colorectal cancer, and breast cancer, when an immune checkpoint drug and the DHB prodrug were combined, they eliminated the tumors, as well as enhancing T cell immune memory, which could potentially prevent cancer’s return.
They also showed that DHB improved the effectiveness of CAR-T (Chimeric Antigen Receptor T-Cell) therapies, in which a person’s own immune cells, T cells, are reengineered to recognize specific proteins on the surface of cancer cells and target them for elimination.