Clinicopathological importance of Bcl-2 and p53 in postmenopausal triple-negative breast carcinoma and association with age.

Appropriate biomarkers are required to predict the clinical outcome of triple-negative breast cancer (TNBC). In this study, we focused on the clinical importance of two representative tumor-associated proteins, Bcl-2 and p53. Bcl-2 expression is usually related to estrogen receptor expression and a favorable outcome in breast cancer. TNBC has been reported to show a high frequency of p53 positivity suggesting TP53 mutations. The expressions of Bcl-2 and p53 were immunohistochemically examined in TNBC involving two age groups of postmenopausal women (≥75 y/o, n = 75; 55-64 y/o, n = 47), who underwent surgery without neoadjuvant therapy. We examined their associations with each other, or with clinicopathological factors including the outcome. Bcl-2 expression was inversely correlated with androgen receptor, apocrine morphology, and p53 expressions, and was an independent predictor of a poor outcome in total or in younger women. p53 positivity was associated with a more favorable outcome than p53 negativity in the younger group. In combined analyzes, none of the twenty Bcl-2-negative/p53-positive cases in the younger group exhibited recurrence, resulting in the independent favorable predictive value of Bcl-2-negative/p53-positive. The anti-apoptotic nature of Bcl-2 may be apparent in TNBC. The excellent outcome of Bcl-2-negative/p53-positive cases in the younger group warrants further combined investigation of Bcl-2/p53 in TNBC.

Japanese Classification of Esophageal Cancer, 12th Edition: Part I.

This is the first half of English edition of Japanese Classification of Esophageal Cancer, 12th Edition that was published by the Japan Esophageal Society in 2022.

Incidence and molecular characteristics of deficient mismatch repair conditions across nine different tumors and identification of germline variants involved in Lynch-like syndrome.

BACKGROUND: Based on molecular characteristics, deficient DNA mismatch repair (dMMR) solid tumors are largely divided into three categories: somatically MLH1-hypermethylated tumors, Lynch syndrome (LS)-associated tumors, and Lynch-like syndrome (LLS)-associated tumors. The incidence of each of these conditions and the corresponding pathogenic genes related to LLS remain elusive. METHODS: We identified dMMR tumors in 3609 tumors from 9 different solid organs, including colorectal cancer, gastric cancer, small-bowel cancer, endometrial cancer, ovarian cancer, upper urinary tract cancer, urinary bladder cancer, prostate cancer, and sebaceous tumor, and comprehensively summarized the characterization of dMMR tumors. Characterization of dMMR tumors were performed as loss of at least one of MMR proteins (MLH1, MSH2, MSH6, and PMS2), by immunohistochemistry, followed by MLH1 promotor methylation analysis and genetic testing for MMR genes where appropriate. Somatic variant analysis of MMR genes and whole exome sequencing (WES) were performed in patients with LLS. RESULTS: In total, the incidence of dMMR tumors was 5.9% (24/3609). The incidence of dMMR tumors and the proportion of the three categorized dMMR tumors varied considerably with different tumor types. One to three likely pathogenic/pathogenic somatic MMR gene variants were detected in 15 out of the 16 available LLS tumors. One patient each from 12 patients who gave consent to WES demonstrated non-MMR germline variants affect function (POLQ or BRCA1). CONCLUSIONS: Our data regarding the LS to LLS ratio would be useful for genetic counseling in patients who are suspected to have LS, though the genetic backgrounds for the pathogenesis of LLS need further investigation.

Japanese Classification of Esophageal Cancer, 12th Edition: Part II.

This is the second half of English edition of Japanese Classification of Esophageal Cancer, 12th Edition that was published by the Japan Esophageal Society in 2022.

Squamous Neoplastic Precursor Lesions of the Esophagus.

Clinicopathological and molecular studies have demonstrated that dysplasia is a precancerous and/or neoplastic lesion with malignant potential. Further, it is subclassified into two grades: high-grade and low-grade dysplasia. High-grade dysplasia is a clinically significant lesion requiring resection or ablation. Low-grade dysplasia has a much lower risk of carcinoma; thus, it should be followed by endoscopic surveillance. Because squamous dysplasia may progress to squamous cell carcinoma, periodic endoscopy is useful to detect the lesion in patients with risk factors. Squamous dysplasia is diagnosed histopathologically by evaluating both cytologic and structural changes.

Concordance between microsatellite instability testing and immunohistochemistry for mismatch repair proteins and efficient screening of mismatch repair deficient gastric cancer.

Microsatellite instability (MSI) testing, an established technique that has gained prominence in recent years for its predictive potential regarding the efficacy of immune checkpoint inhibitors, is used to evaluate DNA mismatch repair (MMR) deficiency (dMMR). As with other methods, the immunohistochemistry (IHC) of MMR proteins is also widely adopted. Although both techniques have been validated, their concordance rate remains unknown, particularly regarding non-colorectal cancer. Therefore, the aim of the present study was to explore and elucidate their concordance in the context of gastric cancer (GC). A total of 489 surgically resected primary GC tissues were analyzed to compare the results yielded by the MSI test and those from IHC. Of 488 GC cases, 56 (11.5%) exhibited a loss of MMR proteins, whereas 52 (10.7%) were classified as high-frequency MSI (MSI-H). The concordance rate between these two categories was 99.2%. The microsatellite markers BAT26 and MONO27 demonstrated 100% sensitivity and 99.5% specificity in detecting dMMR GC. In addition, histopathological analysis revealed that MSI-H was more prevalent in GCs exhibiting coexisting Tub2 and Por1 subtypes. However, four discordant cases were observed. All four cases were microsatellite-stable cases but exhibited loss of MLH1 protein expression with hypermethylation of the MLH1 promoter. The results of the present study highlight that while there is a strong concordance between MSI and IHC testing results for determining dMMR status, IHC testing may offer superior efficacy in detecting dMMR.

Accelerated telomere shortening in adrenal zona reticularis in patients with prolonged critical illness.

Background: The number of patients with prolonged critical illness (PCI) has been increasing in many countries, and the adrenal gland plays an important role in maintaining homeostasis during PCI. Chronic disease burden is reportedly associated with shorter telomere lengths in human tissues. Telomere shortening in human somatic cells is largely dependent on cell divisions, and critically short telomeres lead to cellular dysfunction and aging. However, the association between PCI and telomere lengths in human adrenal cells is poorly understood. In this study, we investigated this association to assess whether the burden of PCI could accelerate the aging process in adrenal cells. Methods: Adrenocortical tissues from patients who died after PCI usually show a diffuse pattern of intracellular cholesterol ester depletion (i.e., lipid depletion). This study examined near-normal adrenal glands obtained from autopsied patients who died suddenly (control group) and lipid-depleted adrenal glands obtained from autopsied patients who died after PCI (PCI group). The control group included 7 men aged 80 to 94 years (mean age: 85.3 years) and 7 women aged 84 to 94 years (mean age: 87.7 years). The PCI group included 10 men aged 71 to 88 years (mean age: 78.8 years) and 8 women aged 77 to 95 years (mean age: 85.6 years). By using quantitative fluorescence in situ hybridization, relative telomere lengths (RTLs) were determined in the parenchymal cells of the three adrenocortical zones (zona glomerulosa, zona fasciculata, and zona reticularis [ZR]) and in the chromaffin cells of the medulla. The number of adrenal parenchymal cells was determined by immunohistochemistry and digital image analysis. Results: RTLs in ZR cells were significantly shorter in the PCI group than in the control group for both men and women (P = 0.0001 for men and P = 0.0012 for women). However, RTLs in the remaining three types of adrenal cells did not differ between the control and PCI groups for both men and women. The number of ZR cells was higher in the PCI group than in the control group for both men and women (P < 0.0001 for both men and women). The proportion of the number of ZR cells to the total number of adrenocortical parenchymal cells was also higher in the PCI group than in the control group (P < 0.0001 for both men and women). The Ki-67 proliferation index in ZR cells was higher in the PCI group than in the control group (P = 0.0039 for men and P = 0.0063 for women). Conclusions: This study demonstrated ZR cell-specific telomere shortening in patients with adrenal lipid depletion who died after PCI. Our results suggest that the reactive proliferation of ZR cells accelerates the telomere shortening and aging process in ZR cells in these patients. The results of our study may contribute to the understanding of adrenal aging during PCI.

Both MLH1 deficiency and BRAFV600E mutation are a unique characteristic of colorectal medullary carcinoma: An observational study.

Although immunohistochemistry (IHC) for mismatch repair (MMR) proteins (MMR IHC) is used to identify DNA MMR status, universal screening of all patients with colorectal cancer (CRC) using a combination of both MMR IHC and genetic testing for the BRAFV600E mutation is limited in Japan. This study aimed to better understand the histopathological characteristics of CRCs, which exhibit both deficient mismatch repair (dMMR) and BRAFV600E mutation. MMR IHC of formalin-fixed paraffin-embedded tissues from tumor areas obtained from 651 patients with CRC who underwent surgical resection at Hamamatsu University Hospital (Hamamatsu, Japan) between August 2016 and March 2022 were used to evaluate MMR status, which was determined by staining for the expression of 4 MMR proteins (MLH1, MSH2, PMS2, and MSH6). All dMMR tumors were additionally evaluated for BRAFV600 mutation status via Sanger sequencing. Patient clinical characteristics (age, sex, tumor location, size, and tumor pathology) were then classified using their dMMR and BRAFV600 mutation statuses. Among the 651 patients with CRC, 58 carried tumors with dMMR, of which 52 were deficiency in MLH1 (dMLH1). Interestingly, all 16 medullary carcinomas that were analyzed showed characteristics corresponding to the presence of both dMLH1 and BRAFV600E mutation (P = .01). These results suggest that colorectal medullary carcinomas can be diagnosed based on their unique characteristics of harboring the BRAFV600E mutation and exhibiting dMLH1 expression.

Clinicopathological and molecular characteristics of gastric papillary adenocarcinoma.

Papillary adenocarcinoma is defined as carcinoma with a well-defined papillary or villous structure. Despite sharing clinicopathological and morphological features with tubular adenocarcinomas, papillary adenocarcinomas frequently show microsatellite instability. The present study aimed to clarify the clinicopathological features, molecular classification, and programmed death-ligand 1 (PD-L1) expression characteristics of papillary adenocarcinoma, especially tumors with microsatellite instability. We examined the microsatellite status and expression of mucin core proteins and PD-L1 as well as the clinicopathological features in 40 gastric papillary adenocarcinomas. Surrogate immunohistochemical analysis of p53 and mismatch repair proteins along with Epstein-Barr virus-encoded RNA in situ hybridization were performed for molecular classification. Female predominance and frequent microsatellite instability were observed in papillary adenocarcinoma in comparison with tubular adenocarcinoma. The presence of microsatellite instability in papillary adenocarcinoma was significantly correlated with older age, tumor-infiltrating lymphocytes, and Crohn's-like lymphoid reactions. Surrogate examination demonstrated that the genomically stable type (17 cases, 42.5%) was the most common, followed by the microsatellite-unstable type (14 cases, 35%). Among the seven cases showing PD-L1-positive expression in tumor cells, four involved carcinomas with microsatellite instability. These results reveal the clinicopathological and molecular characteristics of gastric papillary adenocarcinoma.

Tenascin-C in Tissue Repair after Myocardial Infarction in Humans.

Adverse ventricular remodeling after myocardial infarction (MI) is progressive ventricular dilatation associated with heart failure for weeks or months and is currently regarded as the most critical sequela of MI. It is explained by inadequate tissue repair due to dysregulated inflammation during the acute stage; however, its pathophysiology remains unclear. Tenascin-C (TNC), an original member of the matricellular protein family, is highly up-regulated in the acute stage after MI, and a high peak in its serum level predicts an increased risk of adverse ventricular remodeling in the chronic stage. Experimental TNC-deficient or -overexpressing mouse models have suggested the diverse functions of TNC, particularly its pro-inflammatory effects on macrophages. The present study investigated the roles of TNC during human myocardial repair. We initially categorized the healing process into four phases: inflammatory, granulation, fibrogenic, and scar phases. We then immunohistochemically examined human autopsy samples at the different stages after MI and performed detailed mapping of TNC in human myocardial repair with a focus on lymphangiogenesis, the role of which has recently been attracting increasing attention as a mechanism to resolve inflammation. The direct effects of TNC on human lymphatic endothelial cells were also assessed by RNA sequencing. The results obtained support the potential roles of TNC in the regulation of macrophages, sprouting angiogenesis, the recruitment of myofibroblasts, and the early formation of collagen fibrils during the inflammatory phase to the early granulation phase of human MI. Lymphangiogenesis was observed after the expression of TNC was down-regulated. In vitro results revealed that TNC modestly down-regulated genes related to nuclear division, cell division, and cell migration in lymphatic endothelial cells, suggesting its inhibitory effects on lymphatic endothelial cells. The present results indicate that TNC induces prolonged over-inflammation by suppressing lymphangiogenesis, which may be one of the mechanisms underlying adverse post-infarct remodeling.

Deep learning-based subtyping of gastric cancer histology predicts clinical outcome: a multi-institutional retrospective study.

INTRODUCTION: The Laurén classification is widely used for Gastric Cancer (GC) histology subtyping. However, this classification is prone to interobserver variability and its prognostic value remains controversial. Deep Learning (DL)-based assessment of hematoxylin and eosin (H&E) stained slides is a potentially useful tool to provide an additional layer of clinically relevant information, but has not been systematically assessed in GC. OBJECTIVE: We aimed to train, test and externally validate a deep learning-based classifier for GC histology subtyping using routine H&E stained tissue sections from gastric adenocarcinomas and to assess its potential prognostic utility. METHODS: We trained a binary classifier on intestinal and diffuse type GC whole slide images for a subset of the TCGA cohort (N = 166) using attention-based multiple instance learning. The ground truth of 166 GC was obtained by two expert pathologists. We deployed the model on two external GC patient cohorts, one from Europe (N = 322) and one from Japan (N = 243). We assessed classification performance using the Area Under the Receiver Operating Characteristic Curve (AUROC) and prognostic value (overall, cancer specific and disease free survival) of the DL-based classifier with uni- and multivariate Cox proportional hazard models and Kaplan-Meier curves with log-rank test statistics. RESULTS: Internal validation using the TCGA GC cohort using five-fold cross-validation achieved a mean AUROC of 0.93 ± 0.07. External validation showed that the DL-based classifier can better stratify GC patients' 5-year survival compared to pathologist-based Laurén classification for all survival endpoints, despite frequently divergent model-pathologist classifications. Univariate overall survival Hazard Ratios (HRs) of pathologist-based Laurén classification (diffuse type versus intestinal type) were 1.14 (95% Confidence Interval (CI) 0.66-1.44, p-value = 0.51) and 1.23 (95% CI 0.96-1.43, p-value = 0.09) in the Japanese and European cohorts, respectively. DL-based histology classification resulted in HR of 1.46 (95% CI 1.18-1.65, p-value < 0.005) and 1.41 (95% CI 1.20-1.57, p-value < 0.005), in the Japanese and European cohorts, respectively. In diffuse type GC (as defined by the pathologist), classifying patients using the DL diffuse and intestinal classifications provided a superior survival stratification, and demonstrated statistically significant survival stratification when combined with pathologist classification for both the Asian (overall survival log-rank test p-value < 0.005, HR 1.43 (95% CI 1.05-1.66, p-value = 0.03) and European cohorts (overall survival log-rank test p-value < 0.005, HR 1.56 (95% CI 1.16-1.76, p-value < 0.005)). CONCLUSION: Our study shows that gastric adenocarcinoma subtyping using pathologist's Laurén classification as ground truth can be performed using current state of the art DL techniques. Patient survival stratification seems to be better by DL-based histology typing compared with expert pathologist histology typing. DL-based GC histology typing has potential as an aid in subtyping. Further investigations are warranted to fully understand the underlying biological mechanisms for the improved survival stratification despite apparent imperfect classification by the DL algorithm.

Cardiac mucosa in neonates.

BACKGROUND: The histology of the cardiac mucosa at the esophagogastric junction (EGJ) at birth is still a controversy. We conducted a histopathological study of the EGJ to clarify the morphology, and to determine the presence or absence of cardiac mucosa at birth. SUBJECTS: We examined 43 Japanese neonates and infants that are born prematurely or at full term. Death had occurred between 1 and 231 days after birth. RESULTS: Cardiac mucosa without parietal cells showing positivity for anti-proton pump antibody, adjacent to the most distal squamous epithelium, was observed in 32 (74%) of the 43cases. Such mucosa was evident in neonates that were full-term and had died within 14 days after birth. On the other hand, cardiac mucosa with parietal cells adjacent to squamous epithelium was noted in 10 cases (23%); the remaining one (2%) had columnar-lined esophagus. Squamous and columnar islands were observed in a single histological section from the EGJ in 22 (51%) of the 43 cases. Parietal cells were sparsely or densely present in the gastric antral mucosa. CONCLUSIONS: On the basis of these histological findings, we consider that cardiac mucosa exists in neonates and infants and can be defined as such, irrespective of the presence or absence of parietal cells (so-called oxyntocardiac mucosa). Neonates born prematurely or at full-term have cardiac mucosa in the EGJ just after birth, as is the case for Caucasian neonates.

Morphological study of the phrenic nerve to determine a reference value for the myelinated fiber density in elderly individuals.

Phrenic nerves (PNs) play an important role in respiration; however, very few morphological studies have assessed them. This study aimed to provide control reference values, including the density of large and small myelinated PN fibers, for future pathological studies. We assessed a total of nine nerves from eight cases among consecutive autopsy cases registered to the Brain Bank for Aging Research between 2018 and 2019 (five men and three women, mean age 77.0 ± 7.0 years). The nerves were sampled distally, and their structures were analyzed using semi-thin sections stained with toluidine blue. The mean and standard deviation of the density of each myelinated fiber of the PN was 6908 ± 1132 fibers/mm2 (total myelinated fiber), 4095 ± 586 fibers/mm2 (large diameter myelinated fiber; diameter ≥7 µm), and 2813 ± 629 fibers/mm2 (small diameter myelinated fiber; diameter <7 µm). There was no correlation between myelinated fiber density and age. This study provides the density measurement of the human PN myelinated fiber, and these findings can be used as reference values for the PN in elderly individuals.

Rare germline variants in pancreatic cancer and multiple primary cancers: an autopsy study.

BACKGROUND: There is a lack of information on rare germline variants of pancreatic cancer-predisposing genes. Risk genes for multiple primary cancers may overlap with those for pancreatic cancer. METHODS: A retrospective study of autopsy cases with a negative family history in the Japanese single nucleotide polymorphism for geriatric research database examined rare germline variants in the protein-coding regions of 61 genes. Targeted sequencing of these genes was performed and classified for pathogenicity using the American College of Medical Genetics and Genomics guidelines. Polyphen-2, SIFT and LoFtool algorithms were used to predict damage to protein function. RESULTS: Of the 189 subjects used (90 cancer and 99 non-cancer controls), 72 patients had pancreatic cancer (23 had multiple primary cancers) and 18 had no pancreatic cancer in multiple primary cancers. APC, BRCA2, BUB1B, ENG and MSH6 were associated with cancer predisposition, and pathogenic/likely pathogenic (P/LP) variants occurred in 6% [pancreatic cancer (4/72); all-cancer (5/90)] and 54% (49/90) carried only variants of uncertain significance (VUS) among cancer patients. Of these VUS, in pancreatic cancer patients, four DNA mismatch repair (MMR) genes ( MLH1, MSH2, MSH6 and PMS2 ), and POLQ in men were significantly associated (odds ratio = 3.83; P = 0.025; P = 0.027, respectively). The most abundant predictor of functionally damaging variants was POLQ . CONCLUSIONS: The frequency of P/LP variants in patients with sporadic pancreatic cancer suggests the need for genetic evaluation of individuals with no family history. VUS of MMR genes ( MLH1, MSH2, MSH6 and PMS2 ) and POLQ may be useful in predicting genetic trends in the potential risk of pancreatic cancer, especially in individuals lacking P/LP.

Estrogen Receptor-ß Gene Cytosine-Adenine (ESR2-CA) Repeat Polymorphism in Postmenopausal Colon Cancer.

The pathobiological role of estrogen is controversial in colorectal cancer. Cytosine-adenine (CA) repeat in the estrogen receptor (ER)-ß gene (ESR2-CA) is a microsatellite, as well as representative of ESR2 polymorphism. Though its function is unknown, we previously showed that a shorter allele (germline) increased the risk of colon cancer in older women, whereas it decreased it in younger postmenopausal women. ESR2-CA and ER-ß expressions were examined in cancerous (Ca) and non-cancerous (NonCa) tissue pairs from 114 postmenopausal women, and comparisons were made considering tissue types, age/locus, and the mismatch repair protein (MMR) status. ESR2-CA repeats <22/≥22 were designated as 'S'/'L', respectively, resulting in genotypes SS/nSS (=SL&LL). In NonCa, the rate of the SS genotype and ER-ß expression level were significantly higher in right-sided cases of women ≥70 (≥70Rt) than in those in the others. A decreased ER-ß expression in Ca compared with NonCa was observed in proficient-MMR, but not in deficient-MMR. In NonCa, but not in Ca, ER-ß expression was significantly higher in SS than in nSS. ≥70Rt cases were characterized by NonCa with a high rate of SS genotype or high ER-ß expression. The germline ESR2-CA genotype and resulting ER-ß expression were considered to affect the clinical characteristics (age/locus/MMR status) of colon cancer, supporting our previous findings.

Steep increase in the number of transthyretin-positive cardiac biopsy cases in Japan: evidence obtained by the nation-wide pathology consultation for the typing diagnosis of amyloidosis.

BACKGROUND: In 2019, 2020 and 2022, the Japanese Government approved the use of tafamidis and two technetium-scintigraphies for transthyretin amyloid (ATTR) cardiomyopathy, and announced the patient criteria for tafamidis therapy. In 2018, we had started a nation-wide pathology consultation of amyloidosis. OBJECTIVE: To reveal the impact of approval of tafamidis and technetium-scintigraphy on the diagnosis of ATTR cardiomyopathy. METHODS: Ten institutes participated in this study on the pathology consultation of amyloidosis and shared rabbit polyclonal anti-κ116-133, anti-λ118-134, and anti-transthyretin115-124 antibodies. Proteomic analysis was performed when the typing diagnosis by immunohistochemistry was unavailable. RESULTS: Out of 5400 consultation cases received from April 2018 to July 2022, the type of amyloidosis by immunohistochemistry was determined in 4119 of the 4420 Congo-red positive cases. The incidences of AA, ALκ, ALλ, ATTR, Aß2M and others were 3.2, 11.3, 28.3, 54.9, 0.6 and 1.8%, respectively. Out of 2208 cardiac biopsy cases received, 1503 cases were ATTR positive. There were 4.0 and 4.9 times more total cases and ATTR-positive cases, respectively, in the last 12 months as compared to the first 12 months. CONCLUSIONS: The approval of tafamidis and technetium-scintigraphy raised the awareness of ATTR cardiomyopathy, leading to an upsurge in ATTR-positive cardiac biopsy cases.

Anti-glomerular basement membrane disease developing 3 years after the development of Sweet syndrome and 1 year after the development of anti-neutrophil cytoplasmic antibody-associated vasculitis: a case report.

A 73-year-old Japanese woman, with a history of Sweet syndrome diagnosed 3 years earlier and anti-myeloperoxidase (MPO) antibody anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis diagnosed 1 year earlier, presented with an episode of rapidly progressive glomerulonephritis (RPGN) with anti-glomerular basement membrane (GBM) disease. At the time of diagnosis of the ANCA-associated vasculitis 1 year earlier, serological testing yielded a negative result for anti-GBM antibody. However, at the present visit, serology for anti-MPO antibody was negative, while that for anti-GBM antibody was positive. This is the first report of anti-GBM disease developing sequentially after Sweet syndrome and ANCA-associated vasculitis. This case may provide clues to the potential immunological links among these three distinct conditions.

STNM01, the RNA oligonucleotide targeting carbohydrate sulfotransferase 15, as second-line therapy for chemotherapy-refractory patients with unresectable pancreatic cancer: An open label, phase I/IIa trial.

Background: The impact of stroma-targeting therapy on tumor immune suppression is largely unexplored. An RNA oligonucleotide, STNM01, has been shown to repress carbohydrate sulfotransferase 15 (CHST15) responsible for tumor proteoglycan synthesis and matrix remodeling. This phase I/IIa study aimed to evaluate the safety and efficacy of STNM01 in patients with unresectable pancreatic ductal adenocarcinoma (PDAC). Methods: This was an open-label, dose-escalation study of STNM01 as second-line therapy in gemcitabine plus nab-paclitaxel-refractory PDAC. A cycle comprised three 2-weekly endoscopic ultrasound-guided locoregional injections of STNM01 at doses of 250, 1,000, 2,500, or 10,000 nM in combination with S-1 (80-120 mg twice a day for 14 days every 3 weeks). The primary outcome was the incidence of dose-liming toxicity (DLT). The secondary outcomes included overall survival (OS), tumor response, changes in tumor microenvironment on immunohistopathology, and safety (jRCT2031190055). Findings: A total of 22 patients were enrolled, and 3 cycles were repeated at maximum; no DLT was observed. The median OS was 7.8 months. The disease control rate was 77.3%; 1 patient showed complete disappearance of visible lesions in the pancreas and tumor-draining lymph nodes. Higher tumoral CHST15 expression was associated with poor CD3+ and CD8+ T cell infiltration at baseline. STNM01 led to a significant reduction in CHST15, and increased tumor-infiltrating CD3+ and CD8+ T cells in combination with S-1 at the end of cycle 1. Higher fold increase in CD3+ T cells correlated with longer OS. There were 8 grade 3 adverse events. Interpretation: Locoregional injection of STNM01 was well tolerated in patients with unresectable PDAC as combined second-line therapy. It prolonged survival by enhancing T cell infiltration in tumor microenvironment. Funding: The present study was supported by the Japan Agency for Medical Research and Development (AMED).