Chimeric antigen receptor T cells (CAR-T) and T cell antigen receptor chimeric T cells (TCR-T) are currently the "top stream" in adoptive T cell tumor immunotherapy. In particular, CAR-T therapy, which has been approved by the FDA, is rewriting the treatment paradigm of some hematological tumors.
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CAR-T Cell Anti-Cancer Therapy Ushered in A Revolutionary Breakthrough!
1. CAR-T Cell Anti-Cancer Therapy Ushered in A Revolutionary Breakthrough!
Chimeric antigen receptor T cells (CAR-T) and T cell antigen receptor chimeric T cells (TCR-
T) are currently the "top stream" in adoptive T cell tumor immunotherapy. In particular, CAR-
T therapy, which has been approved by the FDA, is rewriting the treatment paradigm of some
hematological tumors.
However, adoptive T cell therapy remains of little success in solid tumors. The main reason is
that these T cells, which are reinfused into the patient, need to reach the tumor parenchyma
with the peripheral blood circulation "wading" before they can exert a killing effect. In the
road of "killing enemies", the immunosuppressive microenvironment of the body gradually
depletes reinfused T cells and cannot proliferate and survive for a long time.
In order to improve the outcome of adoptive T cell therapy, patients often require prior
radiotherapy or chemotherapy-induced myeloablative therapy. This conditioning regimen
may improve the proliferation and durable viability of adoptive T cells in vivo by balancing
cytokine production in vivo and removing some immunosuppressive cells (such as regulatory
T cells and myeloid-derived suppressor cells) in vivo. However, high-dose chemoradiotherapy
also brings serious side effects to the body, making many patients unable to tolerate
myeloablative regimens and lose the chance of benefit.
Recently, the research team led by K. Christopher Garcia of Stanford University, Carl H. June
of the University of Pennsylvania, and Antoni Ribas and Anusha Kalbasi of the University of
California, Los Angeles, published important research results in Nature.
They designed for the first time a chimeric receptor fused with orthogonal IL-2 receptor (oIL-
2R) and IL-9 receptor (IL-9R) that activates adoptive T cells without the need for prior
chemoradiotherapy for myeloablative treatment and confers a dual phenotype of their stem-
like memory T cells and effector T cells to effectively exert anti-tumor function.
More importantly, this new therapy has been validated in mouse solid tumor models of
melanoma and pancreatic cancer, providing new strategies for the study and application of
adoptive T cells in the treatment of solid tumors.
IL-2 is a cytokine required for proliferation, survival, and functional maintenance of effector T
cells and is an important therapeutic adjunct to adoptive T cells. However, the pleiotropic
effects of IL-2 and the widespread expression of IL-2R also amplify the inhibitory immune
response and systemic toxic side effects, limiting its therapeutic use.
Christopher Garcia's research team has published some pioneering work in Science in 2018.
By genetically modifying IL-2 as well as the extracellular domain (ECD) of the IL-2Rβ chain,
they designed a mouse IL-2/IL-2Rβ orthogonal pair. This T cell expressing orthogonal IL-2Rβ
(o2R) can only be activated by orthogonal IL-2 (oIL-2), thus avoiding the toxicity of activating
other immunosuppressive cells.
2. In this latest study, the investigators hope to investigate the therapeutic potential of other
members of the γc cytokine receptor family (6) using the oIL-2 system. They replaced the
intracellular domain (ICD) of o2R with ICD of the γc cytokines IL-4, IL-7, IL-9, and IL-21
receptors to construct chimeric orthogonal receptors, respectively.
After analysis and screening, it was found that o9R was similar to the known signaling
characteristics of wild-type IL-9 receptor and was able to lead to STAT1, STAT3 and STAT5
phosphorylation.
According to previous studies, IL-9R is mainly expressed in mast cells, memory B cells, innate
lymphocytes and hematopoietic progenitor cells. There are also Th9 isoforms characterized
by IL-9 secretion in T cells. But mouse T cells do not express IL-9R, so IL-9 naturally fails to
activate mouse T cells. When the researchers artificially transduced T cells from mice with IL-
9R, treatment of T cells with IL-9 also caused phosphorylation of STAT1, STAT3, and STAT5.
At the same time, they found that when o9R was activated with MSA-oIL-2, cells expressed
CD62L, Sca-1, and Fas (CD95) more highly, trending toward a stem-like memory T cell
phenotype (Tscm), an important cell type that can survive continuously and exert antitumor
activity in adoptive cell therapy.
Given the unique signal transduction of o9R and the phenotypic characteristics conferring
importance to cells, researchers want to use this newly designed adoptive T cell to treat solid
tumors.
First, they used a B16-F10 mouse melanoma model expressing gp100 antigen using pmel
mouse T cells as a source of modification (the TCR of pmel T cells itself recognizes gp100)
and found that o9R pmel T cells were able to exert significant antitumor effects in combination
with systemic delivery of oIL-2 without prior lymphodepleting radiotherapy.
At the same time, o9R pmel T cells not only infiltrated more in tumors, but also had higher in
vitro cytolytic ability and IFNγ production. Using transcriptome sequencing, the researchers
identified and validated genes involved in determining o9R pmel T cell infiltration, effector
function, and in vivo activity.
They found that o9R, in addition to being able to induce the Tscm phenotype, observed
enrichment of genes associated with T cell activation (Pdcd1, Icos, Entpd1, Lag3, and Havcr2)
and effector function (Ifng, Gzma, and Prf1). In addition, Jun/Fos expression ratio was
increased, suggesting resistance to tumor-induced failure. In the meantime, o9R signaling
downregulates genes associated with T-cell dysfunction (Nr4a1 and Tox). This suggests that
o9R or native IL-9R signaling pathways may induce heterogeneous mixed subsets.
Next, to investigate the role of o9R signaling in CAR-T, the researchers used a model of
immunotherapy resistance, mesothelin-expressing pancreatic cancer mice, and constructed
CARs. Meanwhile, in order to investigate the effect of o9R signaling pathway on CAR-T cell
3. dysfunction in the tumor microenvironment, they designed to deliver oIL-2 (Ad-oIL-2) with
adenoviral vectors only intratumorally.
The results showed that the combination of Ad-oIL-2 plus CAR-o9R achieved a higher
proportion of complete responses (5/12) and longer survival without prior lymphodepleting
chemotherapy. Although CAR-o9R infiltrated fewer tumors than CAR-o2R T cells compared
to the pmel model, the transcriptome changes of CAR-o9R T cells remained similar to o9R
pmel T cells.
So, does this new method have potential for clinical application? The authors designed
human-derived orthogonal IL-2Rβ (ho2R) and chimeric IL-2Rβ-IL-9R (ho9R) and constructed
TCR T cells and CAR-T cells that recognize tumor antigens NY-ESO-1 and mesothelin,
respectively, on this basis. The results showed that, similar to mice, ho9R activated consistent
phosphorylation signaling, stem cell-like functional phenotypes, and stronger multifunctional
effector molecule expression and killing ability.
Overall, this study designed a novel chimeric receptor o9R to engineer T cells, allowing them
to acquire a unique dual identity of stem cell memory T cells and effector T cells that can
survive and proliferate and kill tumors for a long time in vivo.
Whether the cytokine oIL-2 was administered systemically or locally to tumor-bearing mice,
this modified T cell was able to exert a significant antitumor effect in vivo without
chemoradiotherapy myeloablative treatment.
This new approach is undoubtedly important for adoptive T cells in the treatment of solid
tumors. At the same time, this study constructs and validates human-derived o9R T cells in
vitro and also provides attractive data for subsequent clinical translation.