Intercellular communication between cancer cells themselves or with healthy cells in the tumor microenvironment and/or pre-metastatic sites plays an important role in cancer progression and metastasis. In addition to ligand–receptor signaling complexes, extracellular vesicles (EVs) are emerging as novel mediators of intercellular communication both in tissue homeostasis and in diseases such as cancer. EV-mediated transfer of molecular activities impacting morphological features and cell motility from highly metastatic SW620 cells to non-metastatic SW480 cells is a good in vitro example to illustrate the increased malignancy of colorectal cancer leading to its transformation and aggressive behavior. In an attempt to intercept the intercellular communication promoted by EVs, we recently developed a monovalent Fab fragment antibody directed against human CD9 tetraspanin and showed its effectiveness in blocking the internalization of melanoma cell-derived EVs and the nuclear transfer of their cargo proteins into recipient cells. Here, we employed the SW480/SW620 model to investigate the anti-cancer potential of the anti-CD9 Fab antibody. We first demonstrated that most EVs derived from SW620 cells contain CD9, making them potential targets. We then found that the anti-CD9 Fab antibody, but not the corresponding divalent antibody, prevented internalization of EVs from SW620 cells into SW480 cells, thereby inhibiting their phenotypic transformation, i.e., the change from a mesenchymal-like morphology to a rounded amoeboid-like shape with membrane blebbing, and thus preventing increased cell migration. Intercepting EV-mediated intercellular communication in the tumor niche with an anti-CD9 Fab antibody, combined with direct targeting of cancer cells, could lead to the development of new anti-cancer therapeutic strategies.

Gastric cancer (GC) demonstrates frequent alterations in homologous recombination repair (HRR) genes, and preclinical studies have demonstrated a clear synthetic lethality between HRR deficiency (HRD) and PARPi. While such preclinical synthetic lethality has translated into clinical benefits of PARPi in patients with HRD breast, ovarian, pancreatic, or prostate cancer, the therapeutic role of PARPi in GC remains unclear due to molecular heterogeneity and lack of validated biomarkers for patient selection. This review summarizes the mechanistic foundation for PARPi sensitivity in HRR-deficient GC tumors and evaluates emerging biomarkers, including genomic instability scores, RAD51 foci formation, mutational signatures, and candidate genes such as BRCA1/2, PALB2, and BARD1. We highlight key clinical trials and ongoing research aimed at refining patient selection, optimizing combination strategies, and identifying predictive biomarkers. Improving biomarkers to identify bona fide HRD is essential to optimizing PARPi as a valuable treatment option for patients with GC. We outline a pathway for biomarker-guided adoption of PARPi in GC management. Early-phase clinical trials of PARPi monotherapy in GC have yielded limited efficacy, likely due to variable HRD status and other mechanisms of primary resistance. Combining PARPi with chemotherapy, immune checkpoint inhibitors, or anti-angiogenic agents offers strategies to potentially increase the tumor susceptibility to PARPi and overcome resistance.

Gastric cancer (GC), often diagnosed at advanced or metastatic stages, remains a significant clinical challenge requiring novel biomarkers for early detection, risk stratification, and effective, personalized treatment optimization. Emerging evidence underscores a strong association between gut microbiome dysbiosis and GC initiation, progression, and therapeutic outcomes. This review explores the potential of the advanced/metastatic gastric microbiome as a source of diagnostic and targetable biomarkers and its role in modulating responses to immunotherapy. Although Helicobacter pylori (H. pylori) is the most significant risk factor for GC, several other gastrointestinal taxa—including Fusobacterium nucleatum (F. nucleatum)—have been implicated in advanced GC (AGC). At its inception, microbial dysbiosis contributes to chronic inflammation and immune evasion, thereby influencing tumor behavior and treatment efficacy. Integrating microbiome-based biomarkers into risk stratification, GC staging, and targetable treatment frameworks may enhance early detection, inform immunotherapy strategies, and improve patient-specific treatment responses. Bifidobacterium and Lactobacillus rhamnosus GG have the potential to change the immunotherapy framework with their direct influence on dendritic cell (DC) and cytotoxic T cell (CTL) activity. However, clinical translation is impeded by methodological heterogeneity, causality limitations, and a lack of clinical trials. Nonetheless, the integration of microbiome profiling and the development of therapeutic microbiome modulation strategies, such as personalized probiotics regimens and fecal microbiota transplantation, hold substantial potential for improving clinical outcomes and reducing treatment-related toxicity in GC management.

Localized amyloidosis is a rare benign disease characterized by extracellular deposition of misfolded proteins in a specific organ without systemic involvement, which might lead to organ dysfunction. Patients with localized amyloidosis do not develop systemic diseases such as cardiac, renal, hepatic, or nerve involvement. Typically, the localized disease is managed by surgical resection, while the systemic disease is treated with a combination chemotherapy and immunotherapy. However, some patients can have challenging clinical presentations, delaying diagnosis and organ dysfunction, and they might require systemic therapeutic intervention. There is a significant paucity of knowledge and data regarding clinical manifestations and the course of localized amyloidosis in various organs, and management can also be challenging. It is crucial to appropriately balance effective therapy with patient safety as treatment can lead to toxicity. Here, we discuss a series of patients who were presented with localized amyloidosis and one of whom needed systemic therapy.