Tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) are known to play supportive roles in tumor development and progression, but their interactions in colorectal cancer (CRC) remain unclear. Here, we investigated the effects of colon-cancer-derived CAFs on TAM differentiation, migration, and tumor immunity, both in vitro and in vivo. When co-cultured with monocytes, CAFs attracted monocytes and induced their differentiation into M2 macrophages. Immunohistology of surgically resected human CRC specimens and orthotopically transplanted mouse tumors revealed a correlation between numbers of CAFs and numbers of M2 macrophages. In a mouse model of CRC orthotopic transplantation, treatment with an inhibitor of the colony-stimulating factor-1 receptor (PLX3397) depleted M2 macrophages and increased CD8-positive T cells infiltrating the tumor nest. While this treatment had a minor effect on tumor growth, combining PLX3397 with anti-PD-1 antibody significantly reduced tumor growth. RNA-seq following combination therapy showed activation of tumor immunity. In summary, CAFs are involved in the induction and mobilization of M2 macrophage differentiation in the CRC tumor immune microenvironment, and the combination of cancer immunotherapy and PLX3397 may represent a novel therapeutic option for CRC.

A novel large neutral amino acid transporter 1 (LAT1)-specific inhibitor, JPH203, is expected to cause cancer-specific starvation and possess anti-tumor effects; however, its anti-tumor mechanism for colorectal cancer (CRC) remains unclear. We analyzed LAT family gene expressions in public databases using UCSC Xena and evaluated LAT1 protein expression using immunohistochemistry in 154 cases of surgically resected CRC. We also evaluated mRNA expression using polymerase chain reaction in 10 CRC cell lines. Furthermore, JPH203 treatment experiments were conducted in vitro and in vivo using an allogeneic immune-responsive mouse model with abundant stroma created via the orthotopic transplantation of the mouse-derived CRC cell line CT26 and mesenchymal stem cells. The treatment experiments were followed by comprehensive gene expression analyses with RNA sequencing. Database analyses and immunohistochemistry research on clinical specimens revealed that LAT1 expression was cancer-dominant, and its increase was accompanied by tumor progression. In vitro, JPH203 was effective in an LAT1 expression-dependent manner. In vivo, JPH203 treatment considerably reduced tumor size and metastasis, and RNA sequencing-based pathway analysis showed that not only tumor growth and amino acid metabolism pathways, but also stromal activation-related pathways were suppressed. The results of the RNA sequencing were validated in the clinical specimens, as well as both in vitro and in vivo. LAT1 expression in CRC plays an important role in tumor progression. JPH203 may inhibit the progression of CRC and tumor stromal activity.

Inhibition of WEE1, a key regulator of the G2/M checkpoint of the cell cycle, induces apoptosis by initiating mitosis without repairing DNA damage. However, the effects of WEE1 inhibitors on the tumor immune microenvironment in colorectal cancer (CRC) remain unclear. Here, we investigated the association between WEE1 expression and CRC clinicopathological features using surgically resected CRC specimens and assessed the antitumor effects of a WEE1 inhibitor using CRC cell lines and orthotopic transplantation mouse models. WEE1 expression was not correlated with the clinicopathological features of CRC. The WEE1 inhibitor suppressed cell proliferation in a concentration-dependent manner in all CRC cell lines. It also increased the percentage of cells in the G2/M phase and apoptotic cells, especially in cell lines with p53 mutations, but did not alter these cell percentages in most p53 wild-type cell lines. In the orthotopic mouse model of CRC, tumor volume was significantly reduced in the WEE1 inhibitor-treated group compared to that in the control group. RNA sequencing and immunohistochemistry analyses of mouse tumors revealed that treatment with the WEE1 inhibitor activated tumor immunity and suppressed stromal reactions. These results demonstrate the potential antitumor effects of WEE1 inhibitors in CRC, particularly in patients with p53 mutations.

Background/Objectives: Colorectal neoplasia developing from ulcerative colitis mucosa (CRNUC) can be divided into ulcerative colitis-associated neoplasia (UCAN) and non-UCAN; however, it is often difficult to distinguish UCAN from non-UCAN during a biopsy diagnosis. We investigated whether a genomic analysis could improve the diagnostic accuracy of UCAN using biopsy specimens. Methods: In step 1, 14 CRNUCs were used to examine whether the genomic landscape of biopsy and resection specimens matched. In step 2, we investigated the relationship between the genomic landscapes and the pathological diagnosis of 26 CRNUCs. The cancer genome was analyzed by deep sequencing using a custom panel of 27 genes found to be mutated in our previous CRNUC analysis. Results: In step 1, of the 27 candidate genes, 14 were mutated. The concordance rate of the pathogenic mutations in these 14 genes between the biopsy and resection specimens was 29% (4/14), while that of the pathogenic mutations in TP53 and KRAS was 79% (11/14). In step 2, the pathological diagnosis of biopsy specimens using only hematoxylin and eosin (HE) staining had a sensitivity of 33% and an accuracy of 38% for UCAN diagnosis. On the other hand, the combination of the HE pathology and p53 immunohistochemical staining had a sensitivity of 73% and an accuracy of 85% for UCAN diagnosis, while the combination of HE staining and a TP53 mutation had a sensitivity of 87% and an accuracy of 88% for UCAN diagnosis. Conclusions: An evaluation of TP53 mutations in biopsy specimens may be useful for diagnosing UCAN. However, further studies with larger sample sizes are required before this can be applied in clinical practice.

Objectives: Conventional nodular gastritis has been known to be caused by Helicobacter pylori infection. Several cases of gastric mucosa‐associated lymphoid tissue (MALT) lymphoma with non‐H. pylori Helicobacters (NHPH) exhibit endoscopic findings resembling nodular gastritis. Considering the differences in malignancy, distinguishing between these two conditions is crucial. This study aimed to identify the distinguishing endoscopic features of NHPH‐induced gastric MALT lymphoma with nodular gastritis‐like appearance (NHPHi‐MNG) and H.‐induced conventional nodular gastritis (HPi‐NG).Methods: Between 2011 and 2022, we analyzed 17 patients with NHPHi‐MNG and 50 patients with HPi‐NG at Hiroshima University Hospital and evaluated nodule morphology and distribution patterns.Results: Compared with the HPi‐NG group, the NHPHi‐MNG group exhibited significantly larger nodules (2.5 vs. 2.0 mm, P < 0.05) with protruded morphology (protruded/superficial, elevated: 14/3 vs. 8/42, P < 0.05), most prominently in the gastric angulus. The variability in nodule size was significantly higher in the NHPHi‐MNG group than in the HPi‐NG group (0.85 vs. 0.37 mm, P < 0.05), reflecting nodule heterogeneity. The distance from the gastric angulus to the proximal end of the nodular lesions was significantly greater in the NHPHi‐MNG group than in the HPi‐NG group (4.4 vs. 1.7 cm, P < 0.05). The nodules in the HPi‐NG group were smaller, superficial, elevated, and most prominent in the gastric antrum compared with those in the NHPHi‐MNG group. They were predominantly distributed in the gastric antrum with a homogeneous morphology.Conclusion: NHPHi‐MNG and HPi‐NG can be endoscopically differentiated according to nodule morphology and distribution. Recognizing these distinguishing features is essential for an accurate diagnosis.

Background: Nodular gastritis associated with Helicobacter pylori infection (HPi‐NG) has long been recognized. Recently, similar mucosal changes have been reported with non‐ H. pylori Helicobacter (NHPH), including NHPH‐induced gastric mucosa‐associated lymphoid tissue lymphoma with a nodular gastritis‐like appearance (NHPHi‐MNG) and NHPH‐induced nodular gastritis (NHPHi‐NG). However, how bacterial species differences and the presence or absence of malignancy are reflected in endoscopic appearance has not been sufficiently investigated. This study aimed to clarify these relationships and to identify key endoscopic features that differentiate among the three clinically distinct entities. Methods: We retrospectively analyzed 69 patients diagnosed at Hiroshima University Hospital between 2013 and 2024: 11 with NHPHi‐MNG, 12 with NHPHi‐NG, and 46 with HPi‐NG. Endoscopic findings were compared, focusing on three morphological features of the nodules (maximum diameter, size heterogeneity, and shape) and three distributional features (extent of nodularity, extension to the lower gastric body, and predominant site of nodularity), along with patient sex. Diagnostic accuracy was calculated based on combinations of these features. Results: NHPHi‐MNG was differentiated from NHPHi‐NG with 91.3% accuracy when two or more of the three morphological criteria were satisfied. NHPHi‐MNG was distinguished from HPi‐NG with 93.0% accuracy when four or more of seven criteria were fulfilled: the three morphological features, three distributional features, and patient sex. NHPHi‐NG was differentiated from HPi‐NG with 91.4% accuracy when all three distributional features were present. Conclusion: Among the three nodular gastric conditions, the morphological features of nodules reflected the presence or absence of malignancy, whereas the distributional features were associated with the underlying bacterial species. These findings suggest that specific endoscopic features can aid in distinguishing between benign and malignant forms of nodular gastric lesions and between infections with different Helicobacter species, providing important diagnostic guidance.