p38 Kinase: A Key Target for Driving Potent T Cells for Adoptive Immunotherapy
Authors: Jack D. Chan, Paul A. Beavis, Phillip K. Darcy
Journal: Cancer Cell (2020)

In this issue of Cancer Cell, Gurusamy et al. use a CRISPR-Cas9 screening approach to demonstrate that deletion of p38 increases multiple phenotypic qualities of effective anti-tumor T cells. Preconditioning T cells with a p38 inhibitor enhances anti-tumor efficacy of adoptive immunotherapy. In this issue of Cancer Cell, Gurusamy et al. use a CRISPR-Cas9 screening approach to demonstrate that deletion of p38 increases multiple phenotypic qualities of effective anti-tumor T cells. Preconditioning T cells with a p38 inhibitor enhances anti-tumor efficacy of adoptive immunotherapy. Adoptive immunotherapy involving the transfer of tumor-infiltrating lymphocytes or gene-modified T cells expressing T cell receptors (TCRs) or chimeric antigen receptors (CARs) has shown some remarkable effects in patients with advanced melanoma and in a subset of patients with B cell malignancies. Presently, there are two CAR T cell products targeting the CD19 antigen that have recently been approved by the FDA for refractory non-Hodgkin lymphoma and for patients with relapsed or refractory acute lymphoblastic leukemia. However, the majority of common epithelial cancers including breast, prostate, and colon remain refractory to this form of immunotherapy. Reasons underlying these poor responses in the context of solid cancers include inadequate trafficking and persistence of adoptively transferred T cells at the tumor site and the presence of a hostile immunosuppressive tumor microenvironment. To address this, Gurusamy et al. use an innovative gene-editing screening approach involving CRISPR-Cas9 targeting of 25 TCR-driven kinases and evaluate the impact of deleting these kinases on four specific T cell phenotypes that were selected based on their close association with positive outcomes in adoptive immunotherapy, including T cell expansion, memory, oxidative stress (ROS), and genomic stress (γH2AX) (Gurusamy et al., 2020Gurusamy D. Henning A.N. Yamamoto T.N. Yu Z. Zacharakis N. Krishna S. Kishton R.J. Vodnala S.K. Eidizadeh A. Jia L. et al.Multi-phenotype CRISPR-Cas9 screen identifies p38 kinase as a target for adoptive immunotherapies.Cancer Cell. 2020; 37 (this issue): 818-833Abstract Full Text Full Text PDF Scopus (21) Google Scholar). Interestingly, only knockout of Mapk14 (p38) results in an improvement in all four phenotypes in T cells supporting a central regulatory role for this kinase. In further evaluation, the authors find that expansion of human T cells in the presence of the pharmacological p38 inhibitor (p38i) BIRB796 results in enhanced CD62L and CD27 expression in T cells, decreased levels of ROS, and increased both T cell cytokine and cytoloytic activity without effects on expansion or TCR clonality (Figure 1). Strikingly, in the context of adoptive immunotherapy, the transfer of p38i preconditioned TCR (pMel T cells) or gene-engineered anti-CD19 CAR T cells results in more effective anti-tumor responses and long-term survival in mouse models. The increase in therapeutic effects are shown to couple with increased T cell expansion, effector differentiation, and T cell infiltration into the tumor. Several studies involving adoptive immunotherapy have used pharmacological intervention to limit differentiation of T cells in adoptive immunotherapy. Similar to p38i, the use of TWS119, a GSK-3β inhibitor, enhanced the proportion of stem-cell-like memory T cells (Gattinoni et al., 2009Gattinoni L. Zhong X.-S. Palmer D.C. Ji Y. Hinrichs C.S. Yu Z. Wrzesinski C. Boni A. Cassard L. Garvin L.M. et al.Wnt signaling arrests effector T cell differentiation and generates CD8+ memory stem cells.Nat. Med. 2009; 15: 808-813Crossref PubMed Scopus (598) Google Scholar). However, TWS119 was found to limit T cell expansion and cellular metabolism that reduced the overall therapeutic impact. Other studies have used a specific Akt inhibitor during the expansion phase to generate memory-type T cells that have shown increased therapeutic effects in both TCR and CAR adoptive immunotherapy mouse models (Klebanoff et al., 2017Klebanoff C.A. Crompton J.G. Leonardi A.J. Yamamoto T.N. Chandran S.S. Eil R.L. Sukumar M. Vodnala S.K. Hu J. Ji Y. et al.Inhibition of AKT signaling uncouples T cell differentiation from expansion for receptor-engineered adoptive immunotherapy.JCI Insight. 2017; 2: e95103Crossref PubMed Google Scholar). It would be of particular interest in future studies to compare the relative effect of blockade of either the p38 MAPK or PI3K/Akt pathways on anti-tumor effects of adoptively transferred T cells in vivo and whether inhibition of both of these major TCR signaling pathways results in synergistic effects (Figure 1). It is important to note that another advantage of inhibiting these major TCR pathways during the activation and expansion phase, rather than administration of drug after adoptive transfer, is the prevention of potential toxicity. Gurusamy et al. demonstrate that adoptive transfer of p38i-preconditioned pMel T cells or CAR T cells is very effective in early tumor models, leading to long term survival of mice. In future experiments, it will be important to test how effective this approach is in more established tumor models and particularly in the context of solid cancer metastases where immunosuppressive mechanisms within the tumor microenvironment are more likely to have a profound effect on the anti-tumor activity of adoptively transferred T cells. A number of studies have shown increased anti-tumor effects of tumor-reactive T cells following adoptive transfer in preclinical models following combination with checkpoint blockade such as anti-PD-1, and these combinations are now being tested in a number of clinical trials. An important area of investigation would be to determine whether the effects of p38i-preconditioned T cells show greater efficacy in the presence of PD-1 blockade (Figure 1) or other therapies blocking immunosuppressive pathways, such as adenosine through the use of an adenosine A2A receptor antagonist or transforming growth factor (TGF-β) through expression of a TGFβ dominant negative receptor (DNR). Another potential pathway of interest in the context of p38i preconditioning includes blockade of the protein tyrosine phosphatase non-receptor type 2 (PTPN2) that has recently been shown to overcome T cell exhaustion and immunosuppression, resulting in significantly enhanced CAR T cell responses in mouse models (Wiede et al., 2020Wiede F. Lu K.-H. Du X. Liang S. Hochheiser K. Dodd G.T. Goh P.K. Kearney C. Meyran D. Beavis P.A. et al.PTPN2 phosphatase deletion in T cells promotes anti-tumour immunity and CAR T-cell efficacy in solid tumours.EMBO J. 2020; 39: e103637Crossref PubMed Scopus (17) Google Scholar). Gurusamy et al. examine p38i preconditioning on the generation of CAR T cells containing the CD28 co-stimulatory domain. Previous studies have shown that incorporation of other co-stimulatory signaling domains into the CAR resulted in increased persistence of the transferred T cells and improved therapeutic effects, but it remains to be tested whether incorporation of other signaling domains may further increase the effect of p38i-preconditioned T cells (Figure 1). Furthermore, seminal studies have shown that overexpression of transcription factors such as c-Jun in T cells resulted in significantly enhancing the anti-tumor effects and persistence of CAR T cells (Lynn et al., 2019Lynn R.C. Weber E.W. Sotillo E. Gennert D. Xu P. Good Z. Anbunathan H. Lattin J. Jones R. Tieu V. et al.c-Jun overexpression in CAR T cells induces exhaustion resistance.Nature. 2019; 576: 293-300Crossref PubMed Scopus (126) Google Scholar). Studies that have knocked down methyl transferases such as TET methylcytosine dioxygenase 2 (TET2) (Fraietta et al., 2018Fraietta J.A. Nobles C.L. Sammons M.A. Lundh S. Carty S.A. Reich T.J. Cogdill A.P. Morrissette J.J.D. DeNizio J.E. Reddy S. et al.Disruption of TET2 promotes the therapeutic efficacy of CD19-targeted T cells.Nature. 2018; 558: 307-312Crossref PubMed Scopus (260) Google Scholar) or used small molecule epigenetic modifiers have reported increased formation and maintenance of stem cell memory T cell and central memory T cell populations. Hence, it would be of potential interest in future studies to compare the relative efficacy of these approaches with p38i-preconditioned T cells in an adoptive transfer setting. Another promising approach for adoptive immunotherapy that is gaining traction is the use of armored T cells to deliver inflammatory cytokines to the tumor site. Armored CAR T cells expressing cytokines such as IL-12, IL-18 (Hu et al., 2017Hu B. Ren J. Luo Y. Keith B. Young R.M. Scholler J. Zhao Y. June C.H. Augmentation of Antitumor Immunity by Human and Mouse CAR T Cells Secreting IL-18.Cell Rep. 2017; 20: 3025-3033Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar), or CD40L (Kuhn et al., 2019Kuhn N.F. Purdon T.J. van Leeuwen D.G. Lopez A.V. Curran K.J. Daniyan A.F. Brentjens R.J. CD40 Ligand-Modified Chimeric Antigen Receptor T Cells Enhance Antitumor Function by Eliciting an Endogenous Antitumor Response.Cancer Cell. 2019; 35: 473-488.e6Abstract Full Text Full Text PDF PubMed Scopus (57) Google Scholar) have been shown to effectively reprogram the tumor microenvironment, resulting in enhanced anti-tumor effects. In a more recent study, adoptive transfer of CAR T cells constitutively expressing Flt3L drove increased anti-tumor responses and epitope spreading that activated endogenous T cells to recognize non-CAR antigens (Lai et al., 2020Lai J. Mardiana S. House I.G. Sek K. Henderson M.A. Giuffrida L. Chen A.X.Y. Todd K.L. Petley E.V. Chan J.D. et al.Adoptive cellular therapy with Flt3L armored T cells enhance endogenous antitumor responses in solid cancers by dendritic cell mediated epitope spreading.Nat. Immunol. 2020; (Published online May 18, 2020)https://doi.org/10.1038/s41590-020-0676-7Crossref PubMed Scopus (33) Google Scholar). The incorporation of p38i preconditioning in the initial expansion and transduction phase may further increase the beneficial effects of armored CAR T cell therapy by enhancing armored CAR T cell persistence. The advent of gene-editing technology such as CRISPR-Cas9 is revolutionizing the development of more effective adoptive immunotherapies. This is highlighted with recent clinical trials testing the insertion of CAR transgenes into the T Cell Receptor Alpha Constant (TRAC) locus or using CAR T cells with CRISPR-Cas9 deletion of PD-1 (Stadtmauer et al., 2020Stadtmauer E.A. Fraietta J.A. Davis M.M. Cohen A.D. Weber K.L. Lancaster E. Mangan P.A. Kulikovskaya I. Gupta M. Chen F. et al.CRISPR-engineered T cells in patients with refractory cancer.Science. 2020; 367: eaba7365Crossref PubMed Scopus (263) Google Scholar). Gurusamy et al. use a CRISPR-Cas9 gene editing screening approach to identify a specific TCR-regulated kinase, p38, that was found to be a druggable target for improving multiple phenotypic properties of T cells (Gurusamy et al., 2020Gurusamy D. Henning A.N. Yamamoto T.N. Yu Z. Zacharakis N. Krishna S. Kishton R.J. Vodnala S.K. Eidizadeh A. Jia L. et al.Multi-phenotype CRISPR-Cas9 screen identifies p38 kinase as a target for adoptive immunotherapies.Cancer Cell. 2020; 37 (this issue): 818-833Abstract Full Text Full Text PDF Scopus (21) Google Scholar). Of note, these genetic tools also offer the opportunity in the future to examine other parameters such as the effect of regulatory genetic elements on T cell function. The use of p38i-preconditioned T cells or potentially CRISPR-Cas9 deletion of p38 kinase in adoptively transferred T cells shows much promise to significantly enhance anti-tumor effects of T cells in patients. The authors wish to acknowledge funding support from the National Health and Medical Research Council of Australia, the National Breast Cancer Foundation , Cancer Council of Victoria , and the CLEARbridge Foundation . J.D.C. is supported by a Robert Kirby Award (2020). P.A.B. is supported by a National Breast Cancer Foundation Fellowship (ID# ECF-17-005 ). P.K.D. is supported by an NHMRC Senior Research Fellowship ( APP1136680 ). Multi-phenotype CRISPR-Cas9 Screen Identifies p38 Kinase as a Target for Adoptive ImmunotherapiesGurusamy et al.Cancer CellJune 08, 2020In BriefGurusamy et al. identify phenotypes of effective anti-tumor T cells and reveal p38 as a central regulator of therapeutically desired T cell characteristics in a multi-phenotype screen. Inhibition of p38 promotes effective T cell phenotypes and enhances the anti-tumor efficacy of adoptive T cell immunotherapies. Full-Text PDF Open Archive