Science sub-journal: Developed a CAR combined screening method to determine the most effective CAR-T cells for cancer treatment

In recent years, genetically modified immune cells --- equipped with molecular weapons to recognize and destroy tumor cells--- have changed the face of cancer treatment
.
Now, in a new study, researchers from the University of California, San Francisco, have developed a new way to compare large numbers of CAR-T cells, each with slightly different molecular characteristics, to determine which CAR-T cells are most effective and durable
against cancer 。 The results were published in the Nov.
9, 2022 issue of Science Translational Medicine as "Pooled screening of CAR T cells identifies diverse immune signaling domains for next-generation immunotherapies.
"

In the new study, the authors developed this method, called CAR Pooling, to study CAR-T cells
with 40 different chimeric antigen receptors (CARs).
This screening, which can be scaled up in the future to test hundreds or thousands of receptor combinations, has uncovered new and surprising CAR, making these therapeutic CAR-T cells even more powerful
.

Dr.
Kole Roybal, corresponding author and associate professor of microbiology and immunology at the University of California, San Francisco, said, "CAR-T cells are absolutely transformative
for many blood cancer patients.
The new study lays the groundwork
for smarter ways to engineer these cells so that they can function better and longer-lasting and be used to treat more types of cancer.
”

A transformative treatment

As a type of white blood cell, receptors expressed on the surface of T cells recognize foreign substances
in the body.
When a matching molecule or particle binds to a T cell receptor, the T cell initiates an immune response to fend off the invader
.
This type of immune response destroys not only viruses and bacteria, but also cancer cells
.

Before cancer patients receive CAR-T cell therapy, clinicians collect T cells
from the patient's blood or from a healthy donor.
They then genetically engineered the cells in the lab to express a special, cancer-aware CAR
on the cell's surface.
These genetically modified T cells proliferate outside the body and are injected back into the patient
.
The CAR expressed helps these T cells specifically attack cancer cells
.
A variety of CAR-T cells have been approved for the treatment of blood cancers, including lymphoma, leukemia, and multiple myeloma
.

Dr.
Daniel Goodman, a co-first author and a postdoctoral scholar at UCSF, said, "Our ability to extract T cells from the body, add new genetic programs to them, and put them back into patients as a living programmable therapy has had a huge impact
on the treatment of blood diseases and cancers.
" However, if we better understand how to manipulate their signaling and functional properties, this is just the beginning
of what genetically modified cells can do.
”

Scientists have been working to get CAR-T cells to work
against solid tumors.
Even for many blood cancer patients, CAR-T cells work only temporarily or not at
all.

One of the limiting factors in developing new CAR-T cell therapies is the high-throughput technology required to modify and test new CAR; There are hundreds of CARS throughout the immune system, and they can be combined like Lego bricks into thousands of possible combinations
.

Simplify T cell testing

Roybal, Goodman and co-first author Camillia Azimi, a graduate student at the University of California, San Francisco, developed the CAR joint screening to quickly test the effectiveness
of different CARs in one pass.
This screening method generates a DNA library containing many genetic codes encoding CAR, while introducing them into millions of T cells, which are then competed in test tubes for their skills
to survive, grow, recognize and destroy cancer.

Azimi said, "Our approach makes the process of testing new CAR-based therapies much faster
.
Not only does this allow scientists to save time, but also to explore designs
they otherwise wouldn't be able to test alone.
”

Generate and screen CAR pooled libraries
with different signaling domains.
Image from Science Translational Medicine, 2022, doi:10.
1126/scitranslmed.
abm1463
.

For example, among the 40 CARs tested in the new study, there were not only classical T cell receptors (TCRs), but also receptors borrowed from other types of related immune cells
.
For example, a B-cell receptor called BAFF-R is a prime candidate to make T cells particularly effective against cancer
.
"If we didn't take advantage of CAR joint screening, we would never have chosen to test BAFF-R
," Azimi said.
”

When BAFF-R containing CAR-T cells were tested in mice with multiple myeloma, they survived longer and developed cancer rates lower
than mice that received standard CAR-T cells.

A platform that can be used for future research

The authors are planning to expand the use of CAR combined screening to test more receptors
in redesigned T cells.
Eventually, Roybal said, this approach may be able to be used to develop different types of CAR-T cells to treat different types of cancer; When it comes to different cancer types, there may not be a one-size-fits-all answer
.

"We can certainly use CAR combined screening to quickly find the best CAR
for a particular clinical setting," he said.
One set of CAR may be more beneficial for glioblastoma, but the other group of CAR is most beneficial
for myeloma.
”

As the authors screen more and more CARs, they hope to reveal the underlying pattern
of how CAR dominates immune cell activity.
Ultimately, this could lead to more synthetic receptors that could treat not only cancer, but also other diseases
.

"We want to understand how to make up the fundamental parts of these signaling domains and build the next generation of engineered cell therapies
," Goodman said.
The Goodman lab is also working to understand and improve other aspects of CAR-T cells to improve the effectiveness of
this cell therapy.
Roybal said, "There are many ways to genetically modify
these cells.
The progress made so far is only the first step
in a long march.
(Biovalley Bioon.
com)

Resources:

Daniel B.
Goodman et al.
Pooled screening of CAR T cells identifies diverse immune signaling domains for next-generation immunotherapies, Science Translational Medicine, 2022, doi:10.
1126/scitranslmed.
abm1463.