Allosteric AKT Inhibitors Target Synthetic Lethal Vulnerabilities in E-Cadherin-Deficient Cells

Emerging trends in early-onset gastric cancer

ABSTRACT

The incidence of early-onset gastric cancer (EOGC) is consistently increasing, and its etiology is notably complex. This increase may be attributed to distinctive factors that differ from those associated with late-onset gastric cancer (LOGC), including genetic predispositions, dietary factors, gastric microbiota dysbiosis, and screening of high-risk cases. These factors collectively contribute to the onset of cancer. EOGC significantly differs from LOGC in terms of clinicopathological and molecular characteristics. Moreover, multiple differences in prognosis and clinical management also exist. This study aimed to systematically review the latest research advancements in the epidemiological characteristics, etiological factors, clinicopathological and molecular features, prognosis, and treatment modalities of EOGC.

The Impact of Transcriptional Profiling Cadherin Family and Therapeutic Approaches of Gastric Cancer: A Translational Outlook on Multi-omics Data Analysis

The classical cadherin gene has been linked to a variety of human malignancies, including gastric cancer. However, the link between cadherin genes and gastric cancer outcome is still unclear. This study used multi-omics data to examine the cadherin genes that were differentially regulated in gastric cancer. Differential expression of genes, epigenetic, molecular alterations, and protein expression analyses was conducted. Male SD rats were given N-methyl-N-nitrosourea (MNU) to induce stomach carcinoma in order to verify the activation of cadherin genes. CDH5, CDH6, CDH11, and CDH24 levels were found to be considerably higher in gastric cancer and may serve as useful indicators of stomach adenocarcinoma (STAD). Cadherin genes with variable expression had considerably more promoter methylation in cancers than in normal tissues. In individuals with gastric cancer, high expression of these cadherin genes was related to lower total mortality and disease-free survival rates. Furthermore, compared to normal rats, gastric cancer-induced rats had significantly higher expression and distribution of CDH5, CDH6, CDH11, and CDH24. This study sheds new light on the diagnosis and prognosis of gastric cancer by identifying potential prognostic markers such as CDH5, CDH6, CDH11, and CDH24. The multi-omics approach provided a potential tool for target-based therapy by accurately predicting the outcome of stomach cancer. Researchers may gain more knowledge about the role of cadherin genes in the development and dissemination of tumors to the activated rat model of gastric cancer.

Current advances in understanding the molecular profile of hereditary diffuse gastric cancer and its clinical implications

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer syndrome attributed to germline CDH1 mutations that carries a high risk for early onset DGC. HDGC raises a significant health issue due to its high penetrance and mortality unless diagnosed early. The definitive treatment is to undergo prophylactic total gastrectomy which is associated with significant morbidity., highlighting the urgent need for alternative treatment methods. However, there is limited literature examining potential therapeutic strategies building on emerging insights into the molecular basis of progressive lesions in the context of HDGC. The aim of this review is to summarise the current understanding of HDGC in the context of CDH1 pathogenic variants followed by a review of the proposed mechanisms for progression. In addition, we discuss the development of novel therapeutic approaches and highlight pertinent areas for further research. A literature search was therefore performed for relevant studies examining CDH1 germline variants, second-hit mechanisms of CDH1, pathogenesis of HDGC and potential therapeutic strategies in databases, including PubMed, ScienceDirect and Scopus. Germline mutations are mostly truncating CDH1 variants affecting extracellular domains of E-cadherin, generally due to frameshift, single nucleotide variants or splice site mutations. A second somatic hit of CDH1 most commonly occurs via promoter methylation as shown in 3 studies, but studies are limited with a small sample size. The multi-focal development of indolent lesions in HDGC provide a unique opportunity to understand genetic events that drive the transition to the invasive phenotype. To date, a few signalling pathways have been shown to facilitate the progression of HDGC, including Notch and Wnt. In in-vitro studies, the ability to inhibit Notch signalling was lost in cells transfected with mutant forms of E-cadherin, and increased Notch-1 activity correlated with apoptosis resistance. Furthermore, in patient samples, overexpression of Wnt-2 was associated with cytoplasmic and nuclear β-catenin accumulation and increased metastatic potential. As loss-of-function mutations are challenging to target therapeutically, these findings pave the way towards a synthetic lethal approach in CDH1-deficient cells with some promising results in-vitro. In future, if we could better understand the molecular vulnerabilities in HDGC, there may be opportunities to offer alternative treatment pathways to avoid gastrectomy.

Hereditary Diffuse Gastric Cancer

Hereditary diffuse gastric cancer (HDGC) is a dominantly inherited cancer syndrome characterized by a high incidence of diffuse gastric cancer (DGC) and lobular breast cancer (LBC). HDGC is caused by germline mutations in 2 genes involved in the epithelial adherens junction complex, CDH1 and CTNNA1. We discuss the genetics of HDGC and the variability of its clinical phenotype, in particular the variable penetrance of advanced DGC and LBC, both within and between families. We review the pathology of the disease, the mechanism of tumor initiation, and its natural history. Finally, we describe current best practice for the clinical management of HDGC, including emerging genetic testing criteria for the identification of new families, methods for endoscopic surveillance, the complications associated with prophylactic surgery, postoperative quality of life, and the emerging field of HDGC chemoprevention.

The regulatory role of N6-methyladenosine RNA modification in gastric cancer: Molecular mechanisms and potential therapeutic targets

N6-methyladenosinen (m⁶A) methylation is a frequent RNA methylation modification that is regulated by three proteins: "writers", "erasers", and "readers". The m⁶A modification regulates RNA stability and other mechanisms, including translation, cleavage, and degradation. Interestingly, recent research has linked m⁶A RNA modification to the occurrence and development of cancers, such as hepatocellular carcinoma and non-small cell lung cancer. This review summarizes the regulatory role of m⁶A RNA modification in gastric cancer (GC), including targets, the mechanisms of action, and the potential signaling pathways. Our present findings can facilitate our understanding of the significance of m⁶A RNA modification in GC.

Current and future diagnostic and treatment strategies for patients with invasive lobular breast cancer

BACKGROUND

Invasive lobular breast cancer (ILC) is the second most common type of breast cancer after invasive breast cancer of no special type (NST), representing up to 15% of all breast cancers.

DESIGN

Latest data on ILC are presented, focusing on diagnosis, molecular make-up according to the European Society for Medical Oncology Scale for Clinical Actionability of molecular Targets (ESCAT) guidelines, treatment in the early and metastatic setting and ILC-focused clinical trials.

RESULTS

At the imaging level, magnetic resonance imaging-based and novel positron emission tomography/computed tomography-based techniques can overcome the limitations of currently used imaging techniques for diagnosing ILC. At the pathology level, E-cadherin immunohistochemistry could help improving inter-pathologist agreement. The majority of patients with ILC do not seem to benefit as much from (neo-)adjuvant chemotherapy as patients with NST, although chemotherapy might be required in a subset of high-risk patients. No differences in treatment efficacy are seen for anti-human epidermal growth factor receptor 2 (HER2) therapies in the adjuvant setting and cyclin-dependent kinases 4 and 6 inhibitors in the metastatic setting. The clinical utility of the commercially available prognostic gene expression-based tests is unclear for patients with ILC. Several ESCAT alterations differ in frequency between ILC and NST. Germline BRCA1 and PALB2 alterations are less frequent in patients with ILC, while germline CDH1 (gene coding for E-cadherin) alterations are more frequent in patients with ILC. Somatic HER2 mutations are more frequent in ILC, especially in metastases (15% ILC versus 5% NST). A high tumour mutational burden, relevant for immune checkpoint inhibition, is more frequent in ILC metastases (16%) than in NST metastases (5%). Tumours with somatic inactivating CDH1 mutations may be vulnerable for treatment with ROS1 inhibitors, a concept currently investigated in early and metastatic ILC.

CONCLUSION

ILC is a unique malignancy based on its pathological and biological features leading to differences in diagnosis as well as in treatment response, resistance and targets as compared to NST.

Combination of AKT1 and CDH1 mutations predicts primary resistance to immunotherapy in dMMR/MSI-H gastrointestinal cancer

Background

Gastrointestinal (GI) cancer is the second most common cancer type with mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) phenotype that is expected to respond to immune-checkpoint inhibitors (ICIs). However, approximately half of the patients with dMMR/MSI-H GI cancer derive no benefit from ICIs. We sought to identify the predictors of primary resistance to ICIs in dMMR/MSI-H GI cancer.

Methods

Three independent cohorts were included: (1) the discovery cohort (65 patients with dMMR/MSI-H GI cancer) with ICI efficacy data and pre-ICIs tissue samples for genomic profile and tumor immune infiltration; (2) the validation cohort (22 patients with dMMR/MSI-H GI cancer) with ICI efficacy data and pre-ICIs plasma samples for genomic profile; and (3) the TCGA (The Cancer Genome Atlas) cohort not receiving ICIs (152 patients with MSI-H GI cancer) with genomic profile and survival data.

Results

AKT1 and CDH1 mutations were identified as independent predictors of poor progression-free survival (PFS) and primary resistance to ICIs in dMMR/MSI-H GI cancer. We combined these two genes as an immuno-oncology therapy predictor (IOpred), which could recognize 52.4% (11/21) of dMMR/MSI-H patients with primary resistance to ICIs with a positive predictive value (PPV) of 91.7% (11/12). Receiver operating characteristic analysis demonstrated IOpred with a good performance in predicting primary resistance (area under the curve 0.751). Patients with IOpred-Mut (mutant AKT1 or CDH1) GI cancer had significantly shorter PFS (HR=8.36, p<0.001) and overall survival (OS, HR=5.17, p<0.001) than IOpred-WT (wild-type for both AKT1 and CDH1) cases upon ICI treatment. The validation cohort also confirmed the correlation between IOpred-mutation and poorer prognosis (PFS, HR=4.68, p=0.004; OS, HR=15.98, p<0.001) in dMMR/MSI-H patients after ICIs. The PPV of IOpred in identifying primary resistance to ICIs was 80% (4/5) in the validation cohort. Additionally, IOpred-WT patients could be further stratified by tumor mutational burden (TMB), wherein TMB-low patients (TMB ≤26.19 mutations per megabase (Mb)) had a significantly higher primary resistance rate to ICIs (34.8% vs 6.7%, p=0.014) and poorer PFS (HR=3.46, p=0.008) and OS (HR=4.42, p=0.047) than TMB-high patients (TMB >26.19 mutations/Mb).

Conclusions

IOpred was identified as a powerful predictor of primary resistance to ICIs in dMMR/MSI-H GI cancer, which might serve as a promising biomarker to help guide immunotherapy decision-making.

E-Cadherin-Deficient Cells Are Sensitive to the Multikinase Inhibitor Dasatinib

The CDH1 gene, encoding the cell adhesion protein E-cadherin, is one of the most frequently mutated genes in gastric cancer and inactivating germline CDH1 mutations are responsible for the cancer syndrome hereditary diffuse gastric cancer (HDGC). CDH1-deficient gastric cancers exhibit high AKT serine/threonine kinase 3 (AKT3) expression, but specific drugs against this AKT isoform are not available. We therefore used two publicly available datasets to identify AKT3-associated genes which could be used to indirectly target AKT3. Reactome analysis identified an enrichment of extracellular matrix remodelling genes in AKT3-high gastric cancers. Of the 51 genes that were significantly correlated with AKT3 (but not AKT1), discoidin domain receptor tyrosine kinase 2 (DDR2) showed the strongest positive association. Treatment of isogenic human cells and mouse gastric and mammary organoids with dasatinib, a small molecule inhibitor of multiple kinases including SRC, BCR-ABL and DDR2, preferentially slowed the growth and induced apoptosis of E-cadherin-deficient cells. Dasatinib treatment also preferentially slowed the growth of gastric and mammary organoids harbouring both Cdh1 and Tp53 mutations. In organoid models, dasatinib treatment was associated with decreased phosphorylation of total AKT, with a stronger effect seen in Cdh1-deficient organoids. Treatment with combinations of dasatinib and an inhibitor of AKT, MK2206, enhanced the effect of dasatinib in breast MCF10A cells. In conclusion, targeting the DDR2-SRC-AKT3 axis with dasatinib represents a promising approach for the chemoprevention and chemotherapy of gastric and breast cancers lacking E-cadherin.

Diffuse gastric cancer: Emerging mechanisms of tumor initiation and progression

Gastric cancer is globally the fourth leading cause of cancer-related deaths. Patients with diffuse-type gastric cancer (DGC) particularly have a poor prognosis that only marginally improved over the last decades, as conventional chemotherapies are frequently ineffective and specific therapies are unavailable. Early-stage DGC is characterized by intramucosal lesions of discohesive cells, which can be present for many years before the emergence of advanced DGC consisting of highly proliferative and invasive cells. The mechanisms underlying the key steps of DGC development and transition to aggressive tumors are starting to emerge. Novel mouse- and organoid models for DGC, together with multi-omic analyses of DGC tumors, revealed contributions of both tumor cell-intrinsic alterations and gradual changes in the tumor microenvironment to DGC progression. In this review, we will discuss how these recent findings are leading towards an understanding of the cellular and molecular mechanisms responsible for DGC initiation and malignancy, which may provide opportunities for targeted therapies.

E-Cadherin-Deficient Epithelial Cells Are Sensitive to HDAC Inhibitors

Inactivating germline mutations in the CDH1 gene (encoding the E-cadherin protein) are the genetic hallmark of hereditary diffuse gastric cancer (HDGC), and somatic CDH1 mutations are an early event in the development of sporadic diffuse gastric cancer (DGC) and lobular breast cancer (LBC). In this study, histone deacetylase (HDAC) inhibitors were tested for their ability to preferentially inhibit the growth of human cell lines (MCF10A and NCI-N87) and murine organoids lacking CDH1 expression. CDH1^-/- breast and gastric cells were more sensitive to the pan-HDAC inhibitors entinostat, pracinostat, mocetinostat and vorinostat than wild-type cells, with an elevated growth inhibition that was, in part, attributable to increased apoptosis. CDH1-null cells were also sensitive to more class-specific HDAC inhibitors, but compared to the pan-inhibitors, these effects were less robust to genetic background. Increased sensitivity to entinostat was also observed in gastric organoids with both Cdh1 and Tp53 deletions. However, the deletion of Tp53 largely abrogated the sensitivity of the Cdh1-null organoids to pracinostat and mocetinostat. Finally, entinostat enhanced Cdh1 expression in heterozygous Cdh1^+/- murine organoids. In conclusion, entinostat is a promising drug for the chemoprevention and/or treatment of HDGC and may also be beneficial for the treatment of sporadic CDH1-deficient cancers.

Loss of E-Cadherin Leads to Druggable Vulnerabilities in Sphingolipid Metabolism and Vesicle Trafficking

Simple Summary

Germline loss of the CDH1 gene is the primary genetic basis for hereditary diffuse gastric cancer, a disease resulting in elevated risk of both diffuse gastric cancer and lobular breast cancer. Current preventative treatment consists of prophylactic total gastrectomy, a therapy with several associated long-term morbidities. To address the lack of targeted molecular therapies for hereditary diffuse gastric cancer, we have utilized a synthetic lethal approach to identify candidate compounds that can specifically kill CDH1-null cells. Inhibitors of sphingolipid metabolism and vesicle trafficking pathways were identified as promising candidate compounds in a cell line model of CDH1 loss, then further validated in murine-derived organoid models of hereditary diffuse gastric cancer. With further research, these findings may lead to the development of novel chemoprevention strategies for the treatment of hereditary diffuse gastric cancer.

Abstract

Germline inactivating variants of CDH1 are causative of hereditary diffuse gastric cancer (HDGC), a cancer syndrome characterized by an increased risk of both diffuse gastric cancer and lobular breast cancer. Because loss of function mutations are difficult to target therapeutically, we have taken a synthetic lethal approach to identify targetable vulnerabilities in CDH1-null cells. We have previously observed that CDH1-null MCF10A cells exhibit a reduced rate of endocytosis relative to wildtype MCF10A cells. To determine whether this deficiency is associated with wider vulnerabilities in vesicle trafficking, we screened isogenic MCF10A cell lines with known inhibitors of autophagy, endocytosis, and sphingolipid metabolism. Relative to wildtype MCF10A cells, CDH1^−/− MCF10A cells showed significantly greater sensitivity to several drugs targeting these processes, including the autophagy inhibitor chloroquine, the endocytosis inhibitors chlorpromazine and PP1, and the sphingosine kinase 1 inhibitor PF-543. Synthetic lethality was confirmed in both gastric and mammary organoid models of CDH1 loss, derived from CD44-Cre/Cdh1^fl/fl/tdTomato mice. Collectively, these results suggest that both sphingolipid metabolism and vesicle trafficking represent previously unrecognised druggable vulnerabilities in CDH1-null cells and may lead to the development of new therapies for HDGC.

Discovery of AL-GDa62 as a Potential Synthetic Lethal Lead for the Treatment of Gastric Cancer

Diffuse gastric cancer and lobular breast cancer are aggressive malignancies that are frequently associated with inactivating mutations in the tumor suppressor gene CDH1. Synthetic lethal (SL) vulnerabilities arising from CDH1 dysfunction represent attractive targets for drug development. Recently, SLEC-11 (1) emerged as a SL lead in E-cadherin-deficient cells. Here, we describe our efforts to optimize 1. Overall, 63 analogues were synthesized and tested for their SL activity toward isogenic mammary epithelial CDH1-deficient cells (MCF10A-CDH1^-/-). Among the 26 compounds with greater cytotoxicity, AL-GDa62 (3) was four-times more potent and more selective than 1 with an EC₅₀ ratio of 1.6. Furthermore, 3 preferentially induced apoptosis in CDH1^-/- cells, and Cdh1^-/- mammary and gastric organoids were significantly more sensitive to 3 at low micromolar concentrations. Thermal proteome profiling of treated MCF10A-CDH1^-/- cell protein lysates revealed that 3 specifically inhibits TCOF1, ARPC5, and UBC9. In vitro, 3 inhibited SUMOylation at low micromolar concentrations.

Targeting Akt in cancer for precision therapy

Biomarkers-guided precision therapeutics has revolutionized the clinical development and administration of molecular-targeted anticancer agents. Tailored precision cancer therapy exhibits better response rate compared to unselective treatment. Protein kinases have critical roles in cell signaling, metabolism, proliferation, survival and migration. Aberrant activation of protein kinases is critical for tumor growth and progression. Hence, protein kinases are key targets for molecular targeted cancer therapy. The serine/threonine kinase Akt is frequently activated in various types of cancer. Activation of Akt promotes tumor progression and drug resistance. Since the first Akt inhibitor was reported in 2000, many Akt inhibitors have been developed and evaluated in either early or late stage of clinical trials, which take advantage of liquid biopsy and genomic or molecular profiling to realize personalized cancer therapy. Two inhibitors, capivasertib and ipatasertib, are being tested in phase III clinical trials for cancer therapy. Here, we highlight recent progress of Akt signaling pathway, review the up-to-date data from clinical studies of Akt inhibitors and discuss the potential biomarkers that may help personalized treatment of cancer with Akt inhibitors. In addition, we also discuss how Akt may confer the vulnerability of cancer cells to some kinds of anticancer agents.

Molecular target: pan-AKT in gastric cancer

The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway is involved in multiple cellular processes, including cell survival, proliferation, differentiation, metabolism and cytoskeletal reorganisation. The downstream effectors of this PI3K pathway are also essential for maintaining physiologic homeostasis, commonly dysregulated in most solid tumours. AKT is the key regulator in PI3K/AKT/mTOR signalling, interacting with multiple intracellular molecules. AKT activation subsequently leads to a number of potential downstream effects, and its aberrant activation results in the pathogenesis of cancer. Accordingly, as an attractive therapeutic target for cancer treatment, several AKT inhibitors are currently under development and in multiple stages of clinical trials for various types of malignancy, including gastric cancer (GC). Therefore, the authors review the significance of AKT and recent studies on AKT inhibitors in GC, focusing on the scientific background with the potential to improve treatment outcomes.

AKT1/FOXP3 axis-mediated expression of CerS6 promotes p53 mutant pancreatic tumorigenesis

Ceramide synthases (CerSs) catalyze the formation of ceramides from sphingoid bases and acyl-CoA substrates. Increasing evidence suggests that cancer cells generally exhibit altered sphingolipid metabolism in the tumorigenesis of multiple cancers. However, there is no evidence that CerSs are associated with pancreatic ductal carcinoma (PDAC). In the present study, we examined CerS expression in clinical tissue and conducted data mining to investigate the clinical significance of CerSs in the TCGA-PAAD database. We found that high CerS6 expression positively correlated with progression and predicted worse prognosis in PDAC patients, establishing CerS6 as a potential biomarker for PDAC. Furthermore, CerS6 promoted cell proliferation, colony formation and invasion by producing C16-ceramide and was required for tumor formation. Mechanistically, AKT1 interacted with and phosphorylated FOXP3 at S418, which decreased the binding of FOXP3 to the CERS6 promoter and in turn induced CerS6 expression by reconstituting an activated state on the CERS6 promoter. The AKT1/FOXP3 axis mediated the CerS6 expression and promoted p53 mutant pancreatic tumorigenesis by producing excessive C16-ceramide, which induced the accumulation of mutant p53. Thus, our study explores the relationship between PI3K/AKT signaling and sphingolipid metabolism, revealing an oncogenic role for CerS6, which may represent a potential target for PDAC treatment.

Modelling hereditary diffuse gastric cancer initiation using transgenic mouse-derived gastric organoids and single-cell sequencing

Hereditary diffuse gastric cancer (HDGC) is a cancer syndrome caused by germline variants in CDH1, the gene encoding the cell-cell adhesion molecule E-cadherin. Loss of E-cadherin in cancer is associated with cellular dedifferentiation and poor prognosis, but the mechanisms through which CDH1 loss initiates HDGC are not known. Using single-cell RNA sequencing, we explored the transcriptional landscape of a murine organoid model of HDGC to characterize the impact of CDH1 loss in early tumourigenesis. Progenitor populations of stratified squamous and simple columnar epithelium, characteristic of the mouse stomach, showed lineage-specific transcriptional programs. Cdh1 inactivation resulted in shifts along the squamous differentiation trajectory associated with aberrant expression of genes central to gastrointestinal epithelial differentiation. Cytokeratin 7 (CK7), encoded by the differentiation-dependent gene Krt7, was a specific marker for early neoplastic lesions in CDH1 carriers. Our findings suggest that deregulation of developmental transcriptional programs may precede malignancy in HDGC. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

ACOT4 accumulation via AKT-mediated phosphorylation promotes pancreatic tumourigenesis

The acyl-CoA thioesterase (ACOT) family catalyses the hydrolysis of acyl-CoA thioesters to their corresponding non-esterified fatty acid and coenzyme A (CoA). Increasing evidence suggests that cancer cells generally have altered lipid metabolism in different aspects. However, the roles of the ACOT family in cancer, especially in pancreatic ductal carcinoma (PDAC), are largely unknown. In the present study, we mined data to determine the clinical significance of all eleven ACOT genes among nine major solid tumour types from TCGA database and found that the expression of ACOT4 in PDAC was negatively correlated with patient survival, establishing ACOT4 as a potential biomarker of PDAC. Depletion of ACOT4 attenuated the proliferation and tumour formation of PDAC cells. Using mass spectrometry, HSPA1A was found to associate with ACOT4. Furthermore, we found that phosphorylation of ACOT4 at S392 by AKT decreased the binding of ACOT4 to HSPA1A, resulting in ACOT4 accumulation. The ACOT4 elevation promotes pancreatic tumourigenesis by producing excessive CoA to support tumour cell metabolism. Thus, our study expands the relationship between AKT signalling and lipid metabolism and establishes a functional role of ACOT4 in PDAC.

Hereditary diffuse gastric cancer: updated clinical practice guidelines

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer syndrome that is characterised by a high prevalence of diffuse gastric cancer and lobular breast cancer. It is largely caused by inactivating germline mutations in the tumour suppressor gene CDH1, although pathogenic variants in CTNNA1 occur in a minority of families with HDGC. In this Policy Review, we present updated clinical practice guidelines for HDGC from the International Gastric Cancer Linkage Consortium (IGCLC), which recognise the emerging evidence of variability in gastric cancer risk between families with HDGC, the growing capability of endoscopic and histological surveillance in HDGC, and increased experience of managing long-term sequelae of total gastrectomy in young patients. To redress the balance between the accessibility, cost, and acceptance of genetic testing and the increased identification of pathogenic variant carriers, the HDGC genetic testing criteria have been relaxed, mainly through less restrictive age limits. Prophylactic total gastrectomy remains the recommended option for gastric cancer risk management in pathogenic CDH1 variant carriers. However, there is increasing confidence from the IGCLC that endoscopic surveillance in expert centres can be safely offered to patients who wish to postpone surgery, or to those whose risk of developing gastric cancer is not well defined.

Overview on new progress of hereditary diffuse gastric cancer with CDH1 variants

Hereditary diffuse gastric cancer (HDGC), comprising 1%-3% of gastric malignances, has been associated with CDH1 variants. Accumulating evidence has demonstrated more than 100 germline CDH1 variant types. E-cadherin encoded by the CDH1 gene serves as a tumor suppressor protein. CDH1 promoter hypermethylation and other molecular mechanisms resulting in E-cadherin dysfunction are involved in the tumorigenesis of HDGC. Histopathology exhibits characteristic signet ring cells, and immunohistochemical staining may show negativity for E-cadherin and other signaling proteins. Early HDGC is difficult to detect by endoscopy due to the development of lesions beneath the mucosa. Prophylactic gastrectomy is the most recommended treatment for pathogenic CDH1 variant carriers. Recent studies have promoted the progression of promising molecular-targeted therapies and management strategies. This review summarizes recent advances in CDH1 variant types, tumorigenesis mechanisms, diagnosis, and therapy, as well as clinical implications for future gene therapies.

Akt-targeted therapy as a promising strategy to overcome drug resistance in breast cancer - A comprehensive review from chemotherapy to immunotherapy

Breast cancer is the most frequently occurring cancer in women. Chemotherapy in combination with immunotherapy has been used to treat breast cancer. Atezolizumab targeting the protein programmed cell death-ligand (PD-L1) in combination with paclitaxel was recently approved by the Food and Drug Administration (FDA) for Triple-Negative Breast Cancer (TNBC), the most incurable type of breast cancer. However, the use of such drugs is restricted by genotype and is effective only for those TNBC patients expressing PD-L1. In addition, resistance to chemotherapy with drugs such as lapatinib, geftinib, and tamoxifen can develop. In this review, we address chemoresistance in breast cancer and discuss Akt as the master regulator of drug resistance and several oncogenic mechanisms in breast cancer. Akt not only directly interacts with the mitogen-activated protein (MAP) kinase signaling pathway to affect PD-L1 expression, but also has crosstalk with Notch and Wnt/β-catenin signaling pathways involved in cell migration and breast cancer stem cell integrity. In this review, we discuss the effects of tyrosine kinase inhibitors on Akt activation as well as the mechanism of Akt signaling in drug resistance. Akt also has a crucial role in mitochondrial metabolism and migrates into mitochondria to remodel breast cancer cell metabolism while also functioning in responses to hypoxic conditions. The Akt inhibitors ipatasertib, capivasertib, uprosertib, and MK-2206 not only suppress cancer cell proliferation and metastasis, but may also inhibit cytokine regulation and PD-L1 expression. Ipatasertib and uprosertib are undergoing clinical investigation to treat TNBC. Inhibition of Akt and its regulators can be used to control breast cancer progression and also immunosuppression, while discovery of additional compounds that target Akt and its modulators could provide solutions to resistance to chemotherapy and immunotherapy.