PIK3CA mutation subtype delineates distinct immune profiles in gastric carcinoma

Abstract

PIK3CA mutations in cancer regulate tumour immunogenicity. Given that PIK3CA mutation subtypes influence therapeutic responses to AKT inhibitor and that H1047R mutation confers selective growth advantages after immunotherapy, we hypothesised that immune phenotypes may depend on PIK3CA mutation subtypes. We investigated 133 gastric cancers (GCs) harbouring PIK3CA mutation [21 E542K (15.8%), 36 E545X (27.1%), 26 H1047X (19.5%), and 46 others (34.6%)]. Four patients (3.0%) had a combination of mutations (E542K + E545K in 3 patients and E545K + H1047R in 1 patient). Epstein-Barr virus (EBV) and microsatellite instability (MSI) status, PD-L1 (programmed death-ligand 1) combined positive score (CPS), and stromal tumour-infiltrating lymphocytes (TILs) were assessed. Concurrent genomic alterations, GeoMx digital spatial profiling (DSP), and OPAL multiplex immunohistochemistry (mIHC) were analysed, and correlation between the two assays was investigated. Of the 133 PIK3CA-mutant (PIK3CA m ) GCs, MSI-high GC was significantly frequent in the H1047X mutation subtype (p = 0.005), while EBV positivity did not affect the mutation subtypes. There was no significant survival difference between the E542K, E545X, and H1047X subgroups. However, in the subgroup analysis for EBV-positive GC, H1047X m GC showed a trend towards shorter survival than E542K and E545X m GC (p = 0.090 and 0.062). With DSP analysis, H1047X m GC showed elevated VISTA (p = 0.0003), granzyme B (p < 0.0001), CD4 (p = 0.0001), and CD45 (p < 0.0001) expression compared with the E542K m or E545X m GC subgroups, and only VISTA expression remained significant (p < 0.0001) using OPAL mIHC. DSP and OPAL analyses showed a moderate correlation of CD4 (ρ = 0.42, p = 0.004) and CD8 (ρ = 0.62, p < 0.001) expression levels in a comparison of six antibodies. Immune-related protein expression levels were evident when classified by the three PIK3CA hotspot mutations, and H1047X m GC showed the highest immune-related protein expression compared with E542K m or E545X m GC. Our results demonstrated distinct immune profiles in GC with PIK3CA hotspot mutations using GeoMx DSP and OPAL mIHC, and there was a correlation between the two multiplex platforms.

Clinical and Genetic Characteristics of Early and Advanced Gastric Cancer

“…This subgroup displayed decreased PD-L1 expression and lower stromal tumor-infiltrating lymphocytes (TIL) when contrasted with the Epstein-Barr virus-positive (EBV+) and MSI-H subtypes. Strikingly, all patients within the CIN or GS subtype exhibited a lack of response to immune checkpoint inhibitor treatment [22].…”

Age-related Differences in Spatially Resolved Transcriptomic Profiles of Patients With Hormone Receptor-positive Breast Carcinoma

“…UV exposure of each ROI liberated the barcodes (indexing oligonucleotides) from the DSP probes, and the probes were then quantified using the NanoString nCounter system (NanoString Technologies). Using the GeoMx DSP Analysis Suite (NanoString Technologies), quality control and normalization were performed according to the manufacturer's recommendations (28). Briefly, the binding density of probe tags, positive control normalization, minimum nuclei, and surface area count were assessed through quality control.…”

ARID1A Mutations in Gastric Cancer: A Review with Focus on Clinicopathological Features, Molecular Background and Diagnostic Interpretation

“…ARID1A plays a key role in promoting tumorigenesis principally through three mechanisms: increased proliferation, disrupted differentiation, and suppression of apoptosis [ 14 , 15 , 16 , 17 , 18 , 19 ]. Notably, in GCs as well as other tumors, a correlation exists between ARID1A and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α (PIK3CA) mutations [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. In detail, PIK3CA mutations are linked to the EBV subtype in the TCGA classification and are associated with microsatellite-stable (MSS)/TP53 and microsatellite instability (MSI)-High subtypes in the ACRG classification [ 8 , 19 , 20 ].…”