Prevalence and Associations of Beta2-Microglobulin Mutations in MSI-H/dMMR Cancers

Abstract

Microsatellite instability (MSI) has emerged as an important predictor of sensitivity for immunotherapy-based strategies. β-2-Microglobulin (B2M) contains microsatellites within the coding regions and is prone to somatic changes in MSI/mismatch repair deficiency (MSI/dMMR) tumors. To delineate prevalence and associations of B2M mutations in MSI-H/dMMR cancers, we investigated the mutational profile of B2M and clinical and pathological features in gastric cancer (GC), colorectal cancer (CRC), and endometrial cancer (EC) with a high incidence of microsatellite instability-high (MSI-H)/dMMR. Formalin-fixed paraffin-embedded (FFPE) tumor tissues along with matched normal tissues were collected from 108 MSI/dMMR patients with GC, CRC, and EC. Genomic profiling of tissue and blood samples were assessed next-generation sequencing (NGS). Immunohistochemistry (IHC) was used to examine the presence or absence of B2M protein. Alternations in the exonic microsatellite regions of B2M were observed at various but high frequencies (57.5% in CRC, 23.9% in GC, and 13.6% in EC) and in different forms. NGS assay revealed that genes involved in chromatin regulation, the PI3K pathway, the WNT pathway, and mismatch repair were extensively altered in the MSI-H cohort. Signature 6 and 26, 2 of 4 mutational signatures associated with defective DNA mismatch repair, featured with high numbers of small insertion/deletions (INDEL) dominated in all 3 types of cancer. Alternations in the exonic microsatellite regions of B2M were observed at various but high frequencies (57.5% in CRC, 23.9% in GC, and 13.6% in EC) and in different forms. Tumor mutational burden (TMB) was significantly higher in the patients carrying MSI-H/dMMR tumors with B2M mutation than that in patients with wild-type B2M (P = .026).The frame shift alteration occurring at the exonic microsatellite sties caused loss of function of B2M gene. In addition, a case with CRC carrying indels in B2M gene resisted the ICI treatment was reported. In conclusion, patients carrying MSI-H/dMMR tumors with B2M mutation showed significantly higher TMB. Prescription of ICIs should be thoroughly evaluated for these patients.

Navigating the Immune Maze: Pioneering Strategies for Unshackling Cancer Immunotherapy Resistance

“…One of the key genetic changes involves mutations in the beta-2-microglobulin (B2M) gene, a critical component of the major histocompatibility complex (MHC) class I molecules. The MHC class I molecule presents tumor antigens to T cells, and any disruption in this pathway, as caused by B2M mutations, can lead to ineffective T cell-mediated tumor cell lysis [134,135].…”

KNa2Lu(BO3)2: A Rare-Earth Borate Crystal Characterized by an Enhanced Birefringence and Wide Ultraviolet Transparency Range

“…Accordingly, materials containing B 3+ cations and rare-earth cations enrich the structural chemistry with versatile frameworks. 14,16−27 For instance, the rare-earth borate K 5 Mg 2 La 3 (BO 3 ) 6 28 presents a 3D framework structure composed of [LaBO 3 ] ∞ layers derived from [BO 3 ] and [LaO 9 ] units. Na 3 YB 8 O 15 29 showcases a 3D network constructed by fundamental building motifs [B 8 O 17 tionally, rare-earth ions readily form bonds with oxygen ions, resulting in the formation of flexible distorted polyhedra, which enhances the polarizability of structural anisotropy.…”

NaK5La2(SO4)6: Enhanced Birefringence of Multiple-Alkali Metal Sulfate Systems via Rare Earth Metal-Centered Polyhedra

“…31 Compared with SCALP cations, rare earth (RE) cations such as La 3+ , Sc 3+ , Y 3+ , Lu 3+ , and Gd 3+ effectively suppress unfavorable electronic transitions and widen the band gap. 32 Furthermore, the highly distorted REmetal center polyhedra can enhance the optical anisotropy and polarization properties, significantly increasing the birefringence. For example, in the optical material CeF 2 (SO 4 ) 3 , the Ce polyhedra cause the [SO 4 ] tetrahedra to align parallel to the caxis, enhancing optical anisotropy and thereby achieving excellent optical properties.…”