In our recent study, we identified Rab10-positive long tubular endosomes, which originate from macropinocytic cups, as a novel endocytic pathway in RAW264 cells. This pathway is unique because it bypasses the lysosomal degradation route and proceeds toward the Golgi region, distinguishing it from previously known endocytic routes. However, its function remains entirely unknown. Upon exploring the cargo transported by Rab10-positive tubular endosomes, we discovered that PD-L1, a cancer immune checkpoint molecule expressed on cancer cells and macrophage surfaces, was abundantly localized in Rab10-positive tubular structures in RAW264 cells. This suggests that PD-L1 may be a significant cargo for these endosomes in macrophages. These findings offer new insights into the role of Rab10-positive tubular endosomes in the intracellular transport of PD-L1, potentially influencing its expression on the cell surface.

Eribulin, a microtubule inhibitor, is effective as later-line therapy for metastatic breast cancer (MBC) and has been reported to remodel the tumor microenvironment and inhibit epithelial–mesenchymal transition (EMT). However, the association between pretreatment EMT status and eribulin efficacy remains unclear. We retrospectively analyzed 41 patients with MBC (excluding invasive lobular carcinoma) treated with eribulin between 2013 and 2020. Formalin-fixed, paraffin-embedded biopsy specimens were examined by immunohistochemistry (IHC) using anti–E-cadherin (24E10) and anti-vimentin (V9) antibodies. Complete membranous E-cadherin expression (3+) was defined as normal; reduced expression (2+, 1+, 0) as altered. Negative vimentin was considered normal; positive expression, altered. Co-localization of E-cadherin and vimentin was assessed by multi-immunofluorescent staining. Of the 41 patients, 24 responded to eribulin and 17 did not. Progression-free survival (PFS) and overall survival (OS) were significantly longer in responders than in nonresponders (p < 0.001 and p = 0.0044). Altered E-cadherin and/or vimentin expression was more frequently observed in responders (p = 0.013) and associated with longer progression-free survival (p = 0.048). These results suggest that eribulin efficacy may be predicted by altered E-cadherin and vimentin expression before treatment.

Secondary hyperparathyroidism (SHPT) associated with chronic kidney disease (CKD) is characterized by parathyroid hyperplasia, which progresses from diffuse-type to nodular-type lesions. Nodular hyperplasia in SHPT is often considered to exhibit monoclonal proliferation, suggesting a shift toward neoplastic behavior, but the molecular mechanisms underlying this transformation remain poorly defined. In this study, we analyzed 340 surgically resected parathyroid glands from long-term dialysis patients who met clinical indications for parathyroidectomy. Based on histological architecture, lesions were classified into diffuse, nodular, or diffuse-nodular (mixed) hyperplasia. We conducted immunohistochemical analysis of Ki-67 and p16^INK4a (CDKN2A), and further assessed region-specific DNA methylation of the p16^INK4a promoter using a bisulfite padlock probe method combined with rolling circle amplification. Nodular-type lesions exhibited significantly higher Ki-67 indices and lower p16^INK4a expression compared to diffuse-type lesions. In situ methylation analysis revealed increased methylation of the p16^INK4a promoter specifically in nodular regions, suggesting epigenetic silencing. Our findings suggest that p16^INK4a silencing through promoter methylation may play a critical role in the clonal expansion and histopathological transformation of parathyroid tissue in SHPT. These results underscore the importance of epigenetic regulation in SHPT progression and suggest that p16^INK4a methylation could represent a potential biomarker for nodular transformation. The padlock probe–based detection system enabled high-resolution spatial analysis of methylation patterns and may serve as a valuable tool for dissecting epigenetic events in early phase of cellular alterations.