Morphological, clinical and molecular characteristics in ARID1a‑deficient microsatellite‑stable oesophageal adenocarcinoma

Publications describe the relevance of the AT-rich interactive domain-containing protein 1A (ARID1a) mutation in gastric adenocarcinoma, which occurs predominantly in the microsatellite instable (MSI)- and Epstein-Barr virus (EBV)-associated subtypes. It is unclear whether potential therapeutic, prognostic or morphologic descriptions are not epiphenomena of MSI (or EBV). Since personalised therapeutics are largely lacking for oesophageal adenocarcinoma (EAC), clinical trials investigating the efficacy of these therapeutics specifically in this subgroup are useful. To the best of our knowledge, this was the first study analysing the relevant tumour subset of microsatellite-stable (MSS) EAC with loss of function of ARID1a. A total of 875 patients with EAC and data from The Cancer Genome Atlas (TCGA) were analysed. Statistical analyses associating previously known molecular characteristics of the present tumour cohort, overall survival, morphological growth patterns and tumour heterogeneity issues were considered. Subsequently, 10% of EAC were ARID1a-deficient, the majority of which were MSS (7.5%). There was no characteristic growth pattern. Approximately 60% of tumours were PD-L1 positive to varying degrees. TP53 mutations occurred together with ARID1a defective EAC in the present cohort and in the TCGA collective. The extent of 7.5% MSS-EAC with ARID1a loss was unaffected by neoadjuvant therapy. ARID1a loss was often detected to be homogeneous (92%). ARID1a loss is not an epiphenomenon of MSI in EAC. The high homogeneity of ARID1a loss tumour clones could be considered an argument for the effectiveness of potential therapeutics. Since the majority of genomic ARID1a alterations result in protein loss, immunohistochemistry is a useful screening technique, especially in the absence of morphological characteristics.

Epigenetic-related gene mutations serve as potential biomarkers for immune checkpoint inhibitors in microsatellite-stable colorectal cancer

Background

Combination therapy with immune checkpoint inhibitors (ICIs) may benefit approximately 10-20% of microsatellite-stable colorectal cancer (MSS-CRC) patients. However, there is a lack of optimal biomarkers. This study aims to understand the predictive value of epigenetic-related gene mutations in ICIs therapy in MSS-CRC patients.

Methods

We analyzed DNA sequences and gene expression profiles from The Cancer Genome Atlas (TCGA) to examine their immunological features. The Harbin Medical University Cancer Hospital (HMUCH) clinical cohort of MSS-CRC patients was used to validate the efficacy of ICIs in patients with epigenetic-related gene mutations (Epigenetic_Mut).

Results

In TCGA, 18.35% of MSS-CRC patients (78/425) had epigenetic-related gene mutations. The Epigenetic_Mut group had a higher tumor mutation burden (TMB) and frameshift mutation (FS_mut) rates. In all MSS-CRC samples, Epigenetic_Mut was elevated in the immune subtype (CMS1) and had a strong correlation with immunological features. Epigenetic_Mut was also associated with favorable clinical outcomes in MSS-CRC patients receiving anti-PD-1-based therapy from the HMUCH cohort. Using immunohistochemistry and flow cytometry, we demonstrated that Epigenetic_Mut samples were associated with increased anti-tumor immune cells both in tumor tissues and peripheral blood.

Conclusion

MSS-CRC patients with epigenetic regulation impairment exhibit an immunologically active environment and may be more susceptible to treatment strategies based on ICIs.

Wnt signaling in adult intestinal stem cells and cancer

Signaling initiated by secreted glycoproteins of the Wnt family regulates many aspects of embryonic development and it is involved in homeostasis of adult tissues. In the gastrointestinal (GI) tract the Wnt pathway maintains the self-renewal capacity of epithelial stem cells. The stem cell attributes are conferred by mutual interactions of the stem cell with its local microenvironment, the stem cell niche. The niche ensures that the threshold of Wnt signaling in the stem cell is kept in physiological range. In addition, the Wnt pathway involves various feedback loops that balance the opposing processes of cell proliferation and differentiation. Today, we have compelling evidence that mutations causing aberrant activation of the Wnt pathway promote expansion of undifferentiated progenitors and lead to cancer. The review summarizes recent advances in characterization of adult epithelial stem cells in the gut. We mainly focus on discoveries related to molecular mechanisms regulating the output of the Wnt pathway. Moreover, we present novel experimental approaches utilized to investigate the epithelial cell signaling circuitry in vivo and in vitro. Pivotal aspects of tissue homeostasis are often deduced from studies of tumor cells; therefore, we also discuss some latest results gleaned from the deep genome sequencing studies of human carcinomas of the colon and rectum.