Identification of an HLA-A*11:01-restricted neoepitope of mutant PIK3CA and its specific T cell receptors for cancer immunotherapy targeting hotspot driver mutations.

Hotspot driver mutations presented by human leukocyte antigens might be recognized by anti-tumor T cells. Based on their advantages of tumor-specificity and immunogenicity, neoantigens derived from hotspot mutations, such as PIK3CAH1047L, may serve as emerging targets for cancer immunotherapies. NetMHCpan V4.1 was utilized for predicting neoepitopes of PIK3CA hotspot mutation. Using in vitro stimulation, antigen-specific T cells targeting the HLA-A*11:01-restricted PIK3CA mutation were isolated from healthy donor-derived peripheral blood mononuclear cells. T cell receptors (TCRs) were cloned using single-cell PCR and sequencing. Their functionality was assessed through T cell activation markers, cytokine production and cytotoxic response to cancer cell lines pulsed with peptides or transduced genes of mutant PIK3CA. Immunogenic mutant antigens from PIK3CA and their corresponding CD8+ T cells were identified. These PIK3CA mutation-specific CD8+ T cells were subsequently enriched, and their TCRs were isolated. The TCR clones exhibited mutation-specific and HLA-restricted reactivity, demonstrating varying degrees of functional avidity. Identified TCR genes were transferred into CD8+ Jurkat cells and primary T cells deficient of endogenous TCRs. TCR-expressing cells demonstrated specific recognition and reactivity against the PIK3CAH1047L peptide presented by HLA-A*11:01-expressing K562 cells. Furthermore, mutation-specific TCR-T cells demonstrated an elevation in cytokine production and profound cytotoxic effects against HLA-A*11:01+ malignant cell lines harboring PIK3CAH1047L. Our data demonstrate the immunogenicity of an HLA-A*11:01-restricted PIK3CA hotspot mutation and its targeting therapeutic potential, together with promising candidates of TCR-T cell therapy.

Activated PI3Kδ Specifically Perturbs Mouse Regulatory T Cell Homeostasis and Function Leading to Immune Dysregulation.

FOXP3+ regulatory T cells (Treg) are required for maintaining immune tolerance and preventing systemic autoimmunity. PI3Kδ is required for normal Treg development and function. However, the impacts of dysregulated PI3Kδ signaling on Treg function remain incompletely understood. In this study, we used a conditional mouse model of activated PI3Kδ syndrome to investigate the role of altered PI3Kδ signaling specifically within the Treg compartment. Activated mice expressing a PIK3CD gain-of-function mutation (aPIK3CD) specifically within the Treg compartment exhibited weight loss and evidence for chronic inflammation, as demonstrated by increased memory/effector CD4+ and CD8+ T cells with enhanced IFN-γ secretion, spontaneous germinal center responses, and production of broad-spectrum autoantibodies. Intriguingly, aPIK3CD facilitated Treg precursor development within the thymus and an increase in peripheral Treg numbers. Peripheral Treg, however, exhibited an altered phenotype, including increased PD-1 expression and reduced competitive fitness. Consistent with these findings, Treg-specific aPIK3CD mice mounted an elevated humoral response following immunization with a T cell-dependent Ag, which correlated with a decrease in follicular Treg. Taken together, these findings demonstrate that an optimal threshold of PI3Kδ activity is critical for Treg homeostasis and function, suggesting that PI3Kδ signaling in Treg might be therapeutically targeted to either augment or inhibit immune responses.

Class I PI3K regulatory subunits control differentiation of dendritic cell subsets and regulate Flt3L mediated signal transduction.

Dendritic cells (DCs) play pivotal roles in initiating and shaping both innate and adaptive immune responses. The spatiotemporal expression of transcription factor networks and activation of specific signal transduction pathways determine the specification, distribution and differentiation of DC subsets. Even though pioneering studies have established indispensable roles for specific catalytic subunits (p110δ and p110γ) in immune cells, functions of the regulatory subunits, particularly of Class I PI3K, within the hematopoietic system remain incompletely understood. In the study presented here, we deleted the key regulatory subunits-p85α and p85ß of the Class IA PI3K in hematopoietic cells and studied its impact on DC differentiation. Our studies identify that a deficiency of p85 causes increased differentiation of conventional DC (cDC) 2 and plasmacytoid DC (pDC) subsets in the spleen. On the other hand, DC numbers in the bone marrow (BM), thymus and lymph nodes were decreased in p85 mutant mice. Analysis of DC-specific progenitors and precursors indicated increased numbers in the BM and spleen of p85 deficient mice. In-vitro differentiation studies demonstrated augmented DC-differentiation capacities of p85 deficient BM cells in the presence of GM-CSF and Flt3L. BM chimera studies established that p85 deficiency affects DC development through cell intrinsic mechanisms. Molecular studies revealed increased proliferation of DCs and common DC progenitors (CDPs) in the absence of p85 and altered signal transduction pathways in p85 mutant DC subsets in response to Flt3L. In essence, data presented here, for the first time, unequivocally establish that the P85α subunit of class IA PI3Ks has an indispensable role in the development and maintenance of DCs.

Activated Phosphoinositide 3-Kinase δ Syndrome: a Large Pediatric Cohort from a Single Center in China.

PURPOSE: Activated phosphoinositide 3-kinase δ syndrome (APDS) is a primary immunodeficiency first described in 2013, which is caused by gain-of-function mutations in PIK3CD or PIK3R1, and characterized by recurrent respiratory tract infections, lymphoproliferation, herpesvirus infection, autoimmunity, and enteropathy. We sought to review the clinical phenotypes, immunological characteristics, treatment, and prognosis of APDS in a large genetically defined Chinese pediatric cohort. METHODS: Clinical records, radiology examinations, and laboratory investigations of 40 APDS patients were reviewed. Patients were contacted via phone call to follow up their current situation. RESULTS: Sinopulmonary infections and lymphoproliferation were the most common complications in this cohort. Three (10.3%) and five (12.5%) patients suffered localized BCG-induced granulomatous inflammation and tuberculosis infection, respectively. Twenty-seven patients (67.5%) were affected by autoimmunity, while malignancy (7.5%) was relatively rare to be seen. Most patients in our cohort took a combined treatment of anti-infection prophylaxis, immunoglobulin replacement, and immunosuppressive therapy such as glucocorticoid or rapamycin administration. Twelve patients underwent hematopoietic stem cell transplantation (HSCT) and had a satisfying prognosis. CONCLUSION: Clinical spectrum of APDS is heterogeneous. This cohort's high incidence of localized BCG-induced granulomatous inflammation and tuberculosis indicates Mycobacterial susceptibility in APDS patients. Rapamycin is effective in improving lymphoproliferation and cytopenia. HSCT is an option for those who have severe complications and poor response to other treatments.

Overcoming resistance to immune checkpoint therapy in PTEN-null prostate cancer by intermittent anti-PI3Kα/ß/δ treatment.

Combining immune checkpoint therapy (ICT) and targeted therapy holds great promises for broad and long-lasting anti-cancer therapies. However, combining ICT with anti-PI3K inhibitors have been challenging because the multifaceted effects of PI3K on both cancer cells and immune cells within the tumor microenvironment. Here we find that intermittent but not daily dosing of a PI3Kα/ß/δ inhibitor, BAY1082439, on Pten-null prostate cancer models could overcome ICT resistance and unleash CD8+ T cell-dependent anti-tumor immunity in vivo. Mechanistically, BAY1082439 converts cancer cell-intrinsic immune-suppression to immune-stimulation by promoting IFNα/IFNγ pathway activation, ß2-microglubin expression and CXCL10/CCL5 secretion. With its preferential regulatory T cell inhibition activity, BAY1082439 promotes clonal expansion of tumor-associated CD8+ T cells, most likely via tertiary lymphoid structures. Once primed, tumors remain T cell-inflamed, become responsive to anti-PD-1 therapy and have durable therapeutic effect. Our data suggest that intermittent PI3K inhibition can alleviate Pten-null cancer cell-intrinsic immunosuppressive activity and turn "cold" tumors into T cell-inflamed ones, paving the way for successful ICT.

PI3Kδ coordinates transcriptional, chromatin, and metabolic changes to promote effector CD8+ T cells at the expense of central memory.

Patients with activated phosphatidylinositol 3-kinase delta (PI3Kδ) syndrome (APDS) present with sinopulmonary infections, lymphadenopathy, and cytomegalvirus (CMV) and/or Epstein-Barr virus (EBV) viremia, yet why patients fail to clear certain chronic viral infections remains incompletely understood. Using patient samples and a mouse model (Pik3cdE1020K/+ mice), we demonstrate that, upon activation, Pik3cdE1020K/+ CD8+ T cells exhibit exaggerated features of effector populations both in vitro and after viral infection that are associated with increased Fas-mediated apoptosis due to sustained FoxO1 phosphorylation and Fasl derepression, enhanced mTORC1 and c-Myc signatures, metabolic perturbations, and an altered chromatin landscape. Conversely, Pik3cdE1020K/+ CD8+ cells fail to sustain expression of proteins critical for central memory, including TCF1. Strikingly, activated Pik3cdE1020K/+ CD8+ cells exhibit altered transcriptional and epigenetic circuits characterized by pronounced interleukin-2 (IL-2)/STAT5 signatures and heightened IL-2 responses that prevent differentiation to memory-like cells in IL-15. Our data position PI3Kδ as integrating multiple signaling nodes that promote CD8+ T cell effector differentiation, providing insight into phenotypes of patients with APDS.

Strategies to Overcome Failures in T-Cell Immunotherapies by Targeting PI3K-δ and -γ.

PI3K-δ and PI3K-γ are critical regulators of T-cell differentiation, senescence, and metabolism. PI3K-δ and PI3K-γ signaling can contribute to T-cell inhibition via intrinsic mechanisms and regulation of suppressor cell populations, including regulatory T-cells and myeloid derived suppressor cells in the tumor. We examine an exciting new role for using selective inhibitors of the PI3K δ- and γ-isoforms as modulators of T-cell phenotype and function in immunotherapy. Herein we review the current literature on the implications of PI3K-δ and -γ inhibition in T-cell biology, discuss existing challenges in adoptive T-cell therapies and checkpoint blockade inhibitors, and highlight ongoing efforts and future directions to incorporate PI3K-δ and PI3K-γ as synergistic T-cell modulators in immunotherapy.

Predictive Value of the TP53/PIK3CA/ATM Mutation Classifier for Patients With Bladder Cancer Responding to Immune Checkpoint Inhibitor Therapy.

Background: Only a proportion of patients with bladder cancer may benefit from durable response to immune checkpoint inhibitor (ICI) therapy. More precise indicators of response to immunotherapy are warranted. Our study aimed to construct a more precise classifier for predicting the benefit of immune checkpoint inhibitor therapy. Methods: This multi-cohort study examined the top 20 frequently mutated genes in five cohorts of patients with bladder cancer and developed the TP53/PIK3CA/ATM mutation classifier based on the MSKCC ICI cohort. The classifier was then validated in a validation set consisting of IMvigor210 cohort and Broad/Dana-Farber cohort. The molecular profile and immune infiltration characteristics in each subgroup as defined by this classifier were explored. Results: Among all 881 patients with bladder cancer, the mutation frequency of TP53, PIK3CA, and ATM ranked in the top 20 mutated genes. The TP53/PIK3CA/ATM mutation classifier was constructed based on the Memorial Sloan Kettering Cancer Center (MSKCC) ICI cohort and only showed predictive value for patients with bladder cancer who received ICI therapy (median overall survival: low-risk group, not reached; moderate-risk group, 13.0 months; high-risk group, 8.0 months; P<0.0001). Similar results were found in subgroups of MSKCC ICI cohort defined by tumor mutation burden. Multivariate Cox analysis revealed that the risk group defined by the classifier served as an independent prognostic factor for overall survival in patients with bladder cancer. Efficacy of the classifier was verified in a validation set consisting of IMvigor210 cohort and Broad/Dana-Farber cohort. Lower expression of PD-1/PD-L1 and less tumor immune infiltration were observed in the high-risk group than the other two groups of the TCGA cohort and the IMvigor210 cohort. Conclusion: Our study constructed a TP53/PIK3CA/ATM mutation classifier to predict the benefit of immune checkpoint inhibitor therapy for patients with bladder cancer. This classifier can potentially complement the tumor mutation burden and guide clinical ICI treatment decisions according to distinct risk levels.

Phosphoinositide 3-Kinase p110 Delta Differentially Restrains and Directs Naïve Versus Effector CD8+ T Cell Transcriptional Programs.

Phosphoinositide 3-kinase p110 delta (PI3K p110δ) is pivotal for CD8+ T cell immune responses. The current study explores PI3K p110δ induction and repression of antigen receptor and cytokine regulated programs to inform how PI3K p110δ directs CD8+ T cell fate. The studies force a revision of the concept that PI3K p110δ controls metabolic pathways in T cells and reveal major differences in PI3K p110δ regulated transcriptional programs between naïve and effector cytotoxic T cells (CTL). These differences include differential control of the expression of cytolytic effector molecules and costimulatory receptors. Key insights from the work include that PI3K p110δ signalling pathways repress expression of the critical inhibitory receptors CTLA4 and SLAMF6 in CTL. Moreover, in both naïve and effector T cells the dominant role for PI3K p110δ is to restrain the production of the chemokines that orchestrate communication between adaptive and innate immune cells. The study provides a comprehensive resource for understanding how PI3K p110δ uses multiple processes mediated by Protein Kinase B/AKT, FOXO1 dependent and independent mechanisms and mitogen-activated protein kinases (MAPK) to direct CD8+ T cell fate.

Sequential targeting of PI3Kδ and LAG3 as an effective anti-cancer approach.

Emerging studies have demonstrated the potential of PI3Kδ blockade as an immunotherapy for solid tumours. In pre-clinical models, we recently demonstrated that anti-LAG3 immune checkpoint blockade vastly potentiated PI3Kδ-based immunotherapy, enabling successful tumour control in all treated mice.

PI3Kδ Forms Distinct Multiprotein Complexes at the TCR Signalosome in Naïve and Differentiated CD4+ T Cells.

Phosphoinositide 3-kinases (PI3Ks) play a central role in adaptive immunity by transducing signals from the T cell antigen receptor (TCR) via production of PIP3. PI3Kδ is a heterodimer composed of a p110δ catalytic subunit associated with a p85α or p85ß regulatory subunit and is preferentially engaged by the TCR upon T cell activation. The molecular mechanisms leading to PI3Kδ recruitment and activation at the TCR signalosome remain unclear. In this study, we have used quantitative mass spectrometry, biochemical approaches and CRISPR-Cas9 gene editing to uncover the p110δ interactome in primary CD4+ T cells. Moreover, we have determined how the PI3Kδ interactome changes upon the differentiation of small naïve T cells into T cell blasts expanded in the presence of IL-2. Our interactomic analyses identified multiple constitutive and inducible PI3Kδ-interacting proteins, some of which were common to naïve and previously-activated T cells. Our data reveals that PI3Kδ rapidly interacts with as many as seven adaptor proteins upon TCR engagement, including the Gab-family proteins, GAB2 and GAB3, a CD5-CBL signalosome and the transmembrane proteins ICOS and TRIM. Our results also suggest that PI3Kδ pre-forms complexes with the adaptors SH3KBP1 and CRKL in resting cells that could facilitate the localization and activation of p110δ at the plasma membrane by forming ternary complexes during early TCR signalling. Furthermore, we identify interactions that were not previously known to occur in CD4+ T cells, involving BCAP, GAB3, IQGAP3 and JAML. We used CRISPR-Cas9-mediated gene knockout in primary T cells to confirm that BCAP is a positive regulator of PI3K-AKT signalling in CD4+ T cell blasts. Overall, our results provide evidence for a large protein network that regulates the recruitment and activation of PI3Kδ in T cells. Finally, this work shows how the PI3Kδ interactome is remodeled as CD4+ T cells differentiate from naïve T cells to activated T cell blasts. These activated T cells upregulate additional PI3Kδ adaptor proteins, including BCAP, GAB2, IQGAP3 and ICOS. This rewiring of TCR-PI3K signalling that occurs upon T cell differentiation may serve to reduce the threshold of activation and diversify the inputs for the PI3K pathway in effector T cells.

Impaired airway epithelial barrier integrity was mediated by PI3Kδ in a mouse model of lipopolysaccharide-induced acute lung injury.

Cell-cell junctions are critical for the maintenance of cellular as well as tissue polarity and integrity. Dysfunction of airway epithelial barrier has been shown to be involved in the pathogenesis of acute lung injury (ALI). Yet the role of phosphatidylinositol 3-kinase delta (PI3Kδ) in dysregulation of airway epithelial barrier integrity in ALI has not been addressed. Mice were subjected to intratracheal instillation of lipopolysaccharide (LPS) to generate a ALI model. Two pharmacological inhibitors of PI3Kδ, IC87114 and AMG319, were respectively given to the mice. Expression of p110δ and its downstream substrate phospho-AKT (Ser473) was increased in LPS-exposed lungs. These increases were inhibited by IC87114 or AMG319. LPS led to pronounced lung injury that was accompanied by significant airway neutrophil recruitment and bronchial epithelial morphological alterations 72 h after exposure. We also found compromised expression of adherens junction protein E-cadherin and tight junction protein claudin-2 in the airway epithelial cells. Treatment with either IC87114 or AMG319 not only attenuated LPS-induced edema, lung injury and neutrophilc inflammation, reduced total protein concentration and IL-6, TNF-α secretion in BALF, but also restored epithelial E-cadherin and claudin-2 expression. In summary, our results showed that LPS can induce a delayed effect on airway epithelial barrier integrity that is mediated by PI3Kδ in a mouse model of ALI.

Update on Infections in Primary Antibody Deficiencies.

Bacterial respiratory tract infections are the hallmark of primary antibody deficiencies (PADs). Because they are also among the most common infections in healthy individuals, PADs are usually overlooked in these patients. Careful evaluation of the history, including frequency, chronicity, and presence of other infections, would help suspect PADs. This review will focus on infections in relatively common PADs, discussing diagnostic challenges, and some management strategies to prevent infections.

Autoimmune Cytopenias and Dysregulated Immunophenotype Act as Warning Signs of Inborn Errors of Immunity: Results From a Prospective Study.

Inborn errors of immunity (IEI) are genetic disorders characterized by a wide spectrum of clinical manifestations, ranging from increased susceptibility to infections to significant immune dysregulation. Among these, primary immune regulatory disorders (PIRDs) are mainly presenting with autoimmune manifestations, and autoimmune cytopenias (AICs) can be the first clinical sign. Significantly, AICs in patients with IEI often fail to respond to first-line therapy. In pediatric patients, autoimmune cytopenias can be red flags for IEI. However, for these cases precise indicators or parameters useful to suspect and screen for a hidden congenital immune defect are lacking. Therefore, we focused on chronic/refractory AIC patients to perform an extensive clinical evaluation and multiparametric flow cytometry analysis to select patients in whom PIRD was strongly suspected as candidates for genetic analysis. Key IEI-associated alterations causative of STAT3 GOF disease, IKAROS haploinsufficiency, activated PI3Kδ syndrome (APDS), Kabuki syndrome and autoimmune lymphoproliferative syndrome (ALPS) were identified. In this scenario, a dysregulated immunophenotype acted as a potential screening tool for an early IEI diagnosis, pivotal for appropriate clinical management and for the identification of new therapeutic targets.

Comprehensive Immuno-Molecular Profiles for Liposarcoma: Roles of Programmed Death Ligand 1, Microsatellite Instability, and PIK3CA.

BACKGROUND: Developing personalized strategies for cancer has shown good efficacies. METHODS: We assessed the molecular targets programmed death ligand 1 (PD-L1), microsatellite instability (MSI), and PIK3CA. Seventy-four patients with liposarcomas who underwent curative resection were assessed for PD-L1 expression in the tumor and tumor-infiltrating lymphocytes (TILs), mismatch repair proteins (MLH1, PMS2, MSH2, and MSH6) by immunohistochemistry, MSI using polymerase chain reaction, and PIK3CA mutation/amplification using pyrosequencing and fluorescence in situ hybridization. RESULTS: Seventeen (23%) cases were TIL+ (≥1 + expression) and associated with longer 5-year overall survival than those with TIL- tumors (84.4 vs. 60.8%, p = 0.007). Six (35.3%) PD-L1+ tumors were detected only in TIL+ cases, with none detected in tumor cells. Two well-differentiated liposarcomas showed MSI, one low and one high with concurrent loss of MLH1, MSH6, and PMS2. PIK3CA mutation was detected in 7 (9.5%) [exon 9 (n = 4) and exon 20 (n = 3)] and only 1 Q546K mutation was a PD-L1+ tumor. PIK3CA copy number gain was detected in 18 (24.4%) and was associated with TIL+ tumors (p = 0.045). CONCLUSIONS: Our comprehensive immuno-molecular panel suggests that liposarcoma should be categorized based on the molecular genomic subtype for precision medicine.

[Clinical and immunological characteristics of a case with activated phosphoinositide 3-kinase δ syndrome 2].

Objective: To analyze the clinical and immunological characteristics of a patient with activated phosphoinositide 3-kinase δ syndrome 2 (APDS2). Methods: A retrospective analysis of clinical data, immune-related gene sequencing, imaging and laboratory findings of a patient with APDS2 admitted to Children's Hospital of Chongqing Medical University was performed. The absolute and relative numbers of peripheral lymphocyte subsets, immune cell subsets and phenotypes were detected by flow cytometry with the age matched healthy child or the patient's father as a control. Results: A female patient aged 6 years and 4 months old was firstly admitted due to paleness over one month and cough for 7 days in June 2017. The IgA (<0.067 g/L) decreased while the IgM (2.55 g/L) increased. The abdominal ultrasound found hepatomegaly (subcostal 1.7 cm) and splenomegaly (subcostal 3.6 cm), and gene sequencing revealed a heterozygous mutation in the PIK3R1 gene c.1425+1G>A. After the treatment with prednisone which was initiated with a dose of 10 mg/times, 3 times/d and continued and tapered over 7 months, the IgM decreased to normal (1.72 g/L), and the hepatomegaly (subcostal 0 cm) and splenomegaly (subcostal 0.5 cm) were improved. The patient was readmitted due to pale and sallow complexion for half a month in July 2019. The percentage of naive CD4(+)T (0.386) and naive CD8(+)T cells (0.271) were decreased while the percentage of terminally differentiated effector memory CD8(+)T cells (0.377) and transitional B cells (0.223) were increased. The mean fluorescence intensity (MFI) of phosphorylated protein kinase B (AKT) in CD3(+)T, CD4(+)T and CD8(+)T cells were higher in the patient (4 125, 5 213, 3 497) than those in her father (3 434, 3 312, 3 058). The percentage of follicular helper T cell (Tfh) (0.299), Th1 (0.491) and Th1-like cells (0.438) in the patient were higher than those in the healthy control (0.156,0.313,0.303), while the percentage of Th17 (0.126) and Th17-like cells (0.188) were lower than those in the healthy control (0.198, 0.315). And the percentage of CD57 in the patient (0.306) was also higher than that in the healthy control (0.246). Conclusions: The humoral immunity and cellular immunity of APDS2 patient are impaired to varying degrees. The steroid can improve the lymphoproliferation and autoimmune hemolytic anemia in this case.

Activated PI3K-delta syndrome in an Egyptian pediatric cohort with primary immune deficiency.

BACKGROUND: Activated Phospho-Inositide 3 (PI3) Kinases Delta syndrome (APDS) can underlie primary immune deficiency. The prevalence and phenotypic characterization of these patients are not well described in Egypt. OBJECTIVES: To describe patients with APDS in hospitalized children with recurrent respiratory tract infections with suspected primary immune deficiency. METHODS: 79 patients were included in the study. E1021K and E525K mutations of PI3K δ chain gene were screened by Sanger sequencing technique. RESULTS: one patient was heterozygous to E1021K mutation; a female child was diagnosed clinically as Combined Immune Deficiency with CD4 and B lymphopenia and markedly deficient IgG and increased IgM. The E525K mutation was not detected in our cohort. CONCLUSIONS: Screening for APDS in patients with recurrent respiratory tract infections with undefined antibody deficiency or combined immune deficiency with or without bronchiectasis is required. These patients need great attention to benefit from the available treatment. Further studies on the Egyptian population are recommended to increase the knowledge about the prevalence and phenotypic characterization of this disease in Egypt.

Successful Sirolimus Treatment for Korean Patients with Activated Phosphoinositide 3-kinase δ Syndrome 1: the First Case Series in Korea.

Activated phosphoinositide 3-kinase δ syndrome (APDS)1 is caused by gain-of-function mutations in PIK3CD, which encodes the catalytic p110δ subunit of phosphoinositide 3 kinase. We describe three patients with APDS1, the first thereof in Korea. Therein, we investigated clinical manifestations of APDS1 and collected data on the efficacy and safety profile of sirolimus, a mammalian target of rapamycin inhibitor and pathway-specific targeted medicine. The same heterozygous PIK3CD mutation was detected in all three patients (E1021K). After genetic diagnosis, all patients received sirolimus and experienced an excellent response, including amelioration of lymphoproliferation and improvement of nodular mucosal lymphoid hyperplasia in the gastrointestinal tract. The median trough level of sirolimus was 5.5 ng/mL (range, 2.8-7.5) at a dose of 2.6-3.6 mg/m². Two patients who needed high-dose, short-interval, immunoglobulin-replacement treatment (IGRT) had a reduced requirement for IGRT after initiating sirolimus, and the dosing interval was extended from 2 and 3 weeks to 4 weeks. The IgG trough level after sirolimus treatment (median, 594 mg/dL; range, 332-799 mg/dL) was significantly higher than that before sirolimus treatment (median, 290 mg/dL; range, 163-346 mg/dL) (p<0.001). One episode of elevated serum creatinine with a surge of sirolimus (Patient 2) and episodes of neutropenia and oral stomatitis (Patient 1) were observed. We diagnosed the first three patients with APDS1 in Korea. Low-dose sirolimus may alleviate clinical manifestations thereof, including hypogammaglobulinemia.

(3R)-5,6,7-trihydroxy-3-isopropyl-3-methylisochroman-1-one enhanced the therapeutic efficacy of anti-PD1 antibody through inhibiting PI3Kδ/γ.

Purpose: Immunotherapy has demonstrated durable clinical responses in various cancers by disinhibiting the immune system, largely attributed to the success of immune-checkpoint blockade. However, there are still subsets of patients across multiple cancers not showing robust responses to these agents and one significant barrier to their efficacy may be the recruitment of myeloid-derived suppressor cells (MDSCs) into the tumor microenvironment. In this study, we demonstrated that functional inhibition of MDSCs with (3 R)-5,6,7-trihydroxy-3-isopropyl-3-methylisochroman-1-one (TIMO), a potent PI3Kδ/γ inhibitor, enhanced the therapeutic efficacy of anti-PD1 antibody in the tumor model.Materials and methods: A syngeneic ovarian tumor model was established. MDSCs from the peripheral blood and tumor parenchyma were analyzed by flow cytometry. Proliferation and killing effects of T-lymphocytes were measured. IFNγ production was measured by ELISA assay. qPCR and western blot were used to detect the gene and protein expression. Furthermore, the therapeutic effects of TIMO combined with anti-PD1 antibody were assessed by the tumor model.Results: Our data demonstrated that inhibition of granulocytic myeloid-derived suppressor cells (G-MDSCs) function with TIMO could overcome MDSCs-mediated immunosuppression and promote antigen-specific T-lymphocyte responses, resulting in the restoration of cytotoxic T cell-mediated tumor control. We further demonstrated that TIMO and anti-PD1 combination therapy promoted tumor growth control in a syngeneic ovarian tumor model.Conclusions: Our results provided proof of concept for a new combination strategy involving the use of a selective inhibitor of PI3Kδ/γ to inhibit the function of MDSCs to enhance tumor responses to immune checkpoint blocking antibodies.

A Comprehensive Survey of Genomic Alterations in Gastric Cancer Reveals Recurrent Neoantigens as Potential Therapeutic Targets.

Immunotherapy directed against cancer-specific neoantigens derived from non-silent mutants is a promising individualized strategy for cancer treatment. Neoantigens shared across patients could be used as a public resource for developing T cell-based therapy. To identify potential public neoantigens for therapy in gastric cancer (GC), 74 GC patients were enrolled in this study. Combined with the TCGA cohort and other published studies, whole exome sequencing data from 942 GC patients were used to detect somatic mutations and predict neoantigens shared by GC patients. The mutations pattern between our study and the TCGA cohort is comparable, and C > T is the most common substitution. The number of neoantigens was significantly higher in older patients (age ≥60) compared to younger patients (age <60), both in this study and the TCGA cohort. Recurrent neoantigens were found in eight genes (TP53, PIK3CA, PGM5, ERBB3, C6, TRIM49C, OR4C16, and KRAS) in this study. The neoantigen-associated mutations PIK3CA (p.H1047R) and TP53 (p.R175H) are common across several cancer types, indicating their potential usage. Overall, our study illustrates a comprehensive genomic landscape of GC and provides the recurrent neoantigens to facilitate further immunotherapy.