A mosaic adeno-associated virus vector as a versatile tool that exhibits high levels of transgene expression and neuron specificity in primate brain.

Recent emphasis has been placed on gene transduction mediated through recombinant adeno-associated virus (AAV) vector to manipulate activity of neurons and their circuitry in the primate brain. In the present study, we created a novel vector of which capsid was composed of capsid proteins derived from both of the AAV serotypes 1 and 2 (AAV1 and AAV2). Following the injection into the frontal cortex of macaque monkeys, this mosaic vector, termed AAV2.1 vector, was found to exhibit the excellence in transgene expression (for AAV1 vector) and neuron specificity (for AAV2 vector) simultaneously. To explore its applicability to chemogenetic manipulation and in vivo calcium imaging, the AAV2.1 vector expressing excitatory DREADDs or GCaMP was injected into the striatum or the visual cortex of macaque monkeys, respectively. Our results have defined that such vectors secure intense and stable expression of the target proteins and yield conspicuous modulation and imaging of neuronal activity.

[A Case of Autoimmune Acquired Factor XIII Deficiency Diagnosed from Recurrent Postoperative Bleeding].

The patient was a 79-year-old man with ureteroileal anastomotic stricture after a Bricker ileal conduit. Endourological treatment of stenosis was performed via percutaneous nephrostomy and ileal conduit. The patient experienced lower abdominal pain on the following day, and computed tomographic (CT) scan showed hematoma retention around the kidney and active bleeding from the renal artery branches. Transarterial embolisation (TAE) was performed and the bleeding was controlled. Two days later, there was a sudden progression of anemia and CT showed an increase in hematoma around the kidney. We subsequently performed nephrectomy for hemostasis. Five days later, the anemia progressed further. There was hematoma retention in the retroperitoneal cavity, and emergency laparotomy hemostasis was performed. Routine coagulation test results were normal. Heavy bleeding was observed several days after TAE and the possibility of coagulation factor XIII deficiency was considered. Factor XIII deficiency was confirmed by a low factor XIII activity level. The patient was given plasma-derived factor XIII. After receiving factor XIII replacement, factor XIII activity remained unchanged and the patient continued to bleed. Thereafter, a cross-mixing test was performed and the patient was diagnosed with autoimmune acquired factor XIII deficiency. Cortical steroids were administered to remove the factor XIII inhibitor. Steroid administration showed a rapid increase in factor XIII activity, and bleeding symptoms were no longer observed. In cases of serious bleeding of unknown cause with a normal coagulation profile, acquired factor XIII deficiency should be suspected and factor XIII activity measured.

Clinical practice pattern in patients with advanced urothelial cancer who had progressed on pembrolizumab in the pre-enfortumab vedotin era.

OBJECTIVES: Pembrolizumab, an anti-PD-1 monoclonal antibody, revolutionized the treatment for advanced urothelial carcinoma. However, the standard treatment for patients after disease progression with pembrolizumab had not been established until the recent approval of enfortumab vedotin. We analyzed the treatment of these patients in the real world, and the patient background and outcomes. METHODS: We extracted data from 543 patients who experienced progressive disease after pembrolizumab initiation from a Japanese nation-wide cohort of platinum-refractory, metastatic urothelial carcinoma. RESULTS: The median overall survival of the 543 patients was 3.5 months (95% confidence interval 3.0-4.1). Of these, only 20.6% (n = 112) received chemotherapy as a subsequent systemic treatment after progressive disease. The regimen of chemotherapy was very diverse. The median overall survival was 11.9 months (95% confidence interval 9.2-14.7) for patients who received chemotherapy, compared to 2.4 months for those who did not receive chemotherapy (95% confidence interval 2.1-2.9; P < 0.0001). Patients who received subsequent chemotherapy were more likely to have better performance status, neutrophil-to-lymphocyte ratio <3, hemoglobin >11 mg/dL, and history of a single chemotherapeutic regimen at pembrolizumab initiation. CONCLUSIONS: This report highlights the real-world practice of the management after pembrolizumab treatment failure in the pre-enfortumab vedotin era, characterized by infrequent use of subsequent anticancer therapy comprising various regimens, reflecting the lack of a standard treatment. Clinical introduction of enfortumab vedotin is expected to improve treatment outcomes in this setting. The present study will provide important baseline data for evaluating the influence of enfortumab vedotin on clinical practices and outcomes.

[Incidence of Antiresorptive Agent-Related Osteonecrosis of the Jaw in Urologic Cancers].

Antiresorptive agent-related osteonecrosis of the jaw (ARONJ) is a serious adverse event of bone resorption inhibitors (BRIs), such as zoledronic acid and denosumab. Based on the results of phase 3 clinical trials for BRIs, the frequency of ARONJ is 1 to 2%, but the actual frequency is presumed to be higher. We studied 143 patients with urologic cancers with bone metastases who were treated with zoledronic acid or denosumab at our hospital between April 2007 and March 2020. ARONJ occurred in 24 patients (16.8%) ; that is, 14 of the 113 patients (12.4%) who received zoledronic acid alone, 8 of the 24 patients (33.3%) who received denosumab alone, and 2 of the 6 patients (33.3%) who sequentially switched from zoledronic acid to denosumab. ARONJ was cured in 8 patients (33.3%), improved in 3 patients (12.5%), unchanged in 4 patients (16.7%), and worsened in 9 patients (37.5%). The frequency of ARONJ increased as the duration of BRI administration prolonged. Time-to-ARONJ was shorter in patients treated with denosumab than in patients treated with zoledronic acid. The occurrence of ARONJ may be underestimated; therefore, further studies are needed to investigate the actual frequency of ARONJ in Japan.

Specific gene expression in unmyelinated dorsal root ganglion neurons in nonhuman primates by intra-nerve injection of AAV 6 vector.

Adeno-associated virus 6 (AAV6) has been proposed as a potential vector candidate for specific gene expression in pain-related dorsal root ganglion (DRG) neurons, but this has not been confirmed in nonhuman primates. The aim of our study was to analyze the transduction efficiency and target specificity of this viral vector in the common marmoset by comparing it with those in the rat. When green fluorescent protein-expressing serotype-6 vector was injected into the sciatic nerve, the efficiency of gene expression in DRG neurons was comparable in both species. We found that the serotype-6 vector was largely specific to the pain-related ganglion neurons in the marmoset, as well as in the rat, whereas the serotype-9 vector resulted in contrasting effects in the two species. Neither AAV6 nor AAV9 resulted in DRG toxicity when administered via the sciatic nerve, suggesting this as a safer route of sensory nerve transduction than the currently used intrathecal or intravenous administrative routes. Furthermore, the AAV6 vector could be an optimal serotype for gene therapy for human chronic pain that has a minimal effect on other somatosensory functions of DRG neurons.

Impact of the objective response to and number of cycles of platinum-based first-line chemotherapy for metastatic urothelial carcinoma on overall survival of patients treated with pembrolizumab.

OBJECTIVES: To investigate the impact of the number of cycles and objective response to chemotherapy on overall survival in patients with metastatic urothelial carcinoma treated with pembrolizumab. METHODS: This multicenter, retrospective study included 755 patients from 59 institutions with advanced, chemoresistant urothelial carcinoma who received pembrolizumab. The associations of the overall survival with the number of cycles and best objective response were investigated using Cox multiple regression analysis. RESULTS: Overall, 391 patients received standard first-line chemotherapy and pembrolizumab as a second-line treatment, and were included in the final analysis. Of the 391 patients, 185 received less than four cycles, 134 received four to six cycles and 72 received more than six cycles of first-line chemotherapy. An objective response (complete or partial response) to chemotherapy was observed in 145 patients (37.1%). Univariate analysis showed that the overall survival of patients who received more than six cycles or responded to chemotherapy (complete or partial response) was significantly longer than that of patients who received less than four cycles or did not respond to chemotherapy (stable or progressive disease). At multivariate levels, no correlations were observed between overall survival and the number of cycles of or the response to chemotherapy. CONCLUSIONS: Therapeutic benefit of pembrolizumab can be expected irrespective of the objective response to and number of cycles of platinum-based first-line chemotherapy.

Retrograde Transgene Expression via Neuron-Specific Lentiviral Vector Depends on Both Species and Input Projections.

For achieving retrograde gene transfer, we have so far developed two types of lentiviral vectors pseudotyped with fusion envelope glycoprotein, termed HiRet vector and NeuRet vector, consisting of distinct combinations of rabies virus and vesicular stomatitis virus glycoproteins. In the present study, we compared the patterns of retrograde transgene expression for the HiRet vs. NeuRet vectors by testing the cortical input system. These vectors were injected into the motor cortex in rats, marmosets, and macaques, and the distributions of retrograde labels were investigated in the cortex and thalamus. Our histological analysis revealed that the NeuRet vector generally exhibits a higher efficiency of retrograde gene transfer than the HiRet vector, though its capacity of retrograde transgene expression in the macaque brain is unexpectedly low, especially in terms of the intracortical connections, as compared to the rat and marmoset brains. It was also demonstrated that the NeuRet but not the HiRet vector displays sufficiently high neuron specificity and causes no marked inflammatory/immune responses at the vector injection sites in the primate (marmoset and macaque) brains. The present results indicate that the retrograde transgene efficiency of the NeuRet vector varies depending not only on the species but also on the input projections.

[A Case of Pelvic Unicentric Castleman Disease Treated by Preoperative Transcatheter Arterial Embolization and Tumor Complete Resection with Combined Lower Abdominal and Posterior Approach].

A 22-year-old woman was referred to our hospital for further examination of an incidentally discovered hypervascular pelvic tumor with a maximum diameter of 10 cm. Although Castleman disease was suspected based on the imaging findings and pathologic findings of the needle biopsy, a definitive diagnosis was not made. Preoperative transcatheter arterial embolization was performed to decrease intraoperative bleeding, and tumor resection was performed on the following day. As for posterior approach prior to anterior approach, the patient was placed in a prone position, and the dorsal aspect of tumor was approached through the dissection of gluteal muscles. Then, dilated branches of the internal iliac vein was found on the tumor capsule, which were safely ligated under direct vision with favorable visual field. Then, the patient was placed in a supine position, the tumor was completely resected by anterior approach without transfusion. Histopathological diagnosis was Castleman disease hyaline vascular type. The patient was discharged without complication and has been free from recurrence for 6 months after surgery.

Pembrolizumab for treating advanced urothelial carcinoma in patients with impaired performance status: Analysis of a Japanese nationwide cohort.

BACKGROUND: The benefits of pembrolizumab in patients with advanced urothelial carcinoma (UC) and impaired performance status (PS) remain unknown. This study assessed the safety and efficacy of pembrolizumab in patients with platinum-refractory UC and Eastern Cooperative Oncology Group PS ≥2 to identify which subgroups may benefit from this drug. METHODS: This retrospective nationwide cohort study collected clinicopathological information for 755 patients from 59 institutions. The overall response rate (ORR) and overall survival (OS) were compared among the patients with PS 0-1, 2, and 3-4. Multivariate analysis was conducted to identify factors predicting OS in patients with PS ≥2. RESULTS: The numbers of patients with PS 0-1, 2, and 3-4 were 602, 98, and 55, respectively; the ORRs in these groups were 29.5, 15.3, and 9.1%, respectively, and the median OS times were 14.3, 3.1, and 2.4 months, respectively. In multivariate Cox regression analysis, a neutrophil-lymphocyte ratio (NLR) ≥3.5 (hazard ratio [HR] = 1.897) and liver metastasis (HR = 2.072) were associated with OS in the PS ≥2 subgroup. The median OS of patients with PS ≥2 without either risk factor was 6.8 months, compared with 3.1 months for patients with one risk factor and 2.3 months for patients with both risk factors. CONCLUSIONS: PS ≥2 portended worse ORR and OS than PS ≤1 despite a comparable safety profile. Among the patients with impaired PS, patients with NLR <3.5 and no liver metastasis may most greatly benefit from pembrolizumab therapy.

The association between missense polymorphisms in SRD5A2 and HSD3B1 and treatment failure with abiraterone for castration-resistant prostate cancer.

Missense polymorphism in HSD3B1, encoding 3ß-hydroxysteroid dehydrogenase-1, was associated with outcome after abiraterone treatment. Other androgen-metabolizing enzymes may be involved in therapeutic effect in abiraterone. In this study, we investigated the significance of polymorphisms in genes involved in androgen and abiraterone metabolisms in prostate cancer patients treated with abiraterone. A total of 99 Japanese male castration-resistant prostate cancer patients treated with abiraterone between 2014 and 2018 were included. Genomic DNA was obtained from whole blood samples, and genotyping on SRD5A2 (rs523349), CYP17A1 (rs743572), CYP17A1 (rs2486758), and AKR1C3 (rs12529) was performed by PCR-based technique. Among the 99 patients, 32 (32.3%), 49 (49.5%), and 18 patients (18.2%) carried GG, GC, and CC alleles in SRD5A2, respectively. CC allele was associated with lower risk of treatment failure (hazard ratio, 0.43; 95% confidence interval, 0.20-0.87; P = 0.017) on multivariate analyses, compared with GG/GC alleles. In the combination model using HSD3B1 and SRD5A2 polymorphisms, compared with the combination of AA in HSD3B1 and GG/GC in SRD5A2, other combinations were associated with lower risk of treatment failure (hazard ratio, 0.34; 95% confidence interval, 0.17-0.62; P = 0.0003) on multivariate analyses. This study showed that SRD5A2 genetic variation was associated with the risk of treatment failure in abiraterone. Combinational use of genetic variation in HSD3B1 with SRD5A2 genetic variation augmented the ability of prognostic stratification.

Biogenic manganese oxides combined with 1-hydroxybenzotriazol and an Mn(II)-oxidizing enzyme from Pleosporales sp. Mn1 oxidize 3,4-dimethoxytoluene to yield 3,4-dimethoxybenzaldehyde.

Using soil samples, we screened for microbes that produce biogenic manganese oxides (BMOs) and isolated Mn(II)-oxidizing fungus, namely Pleosporales sp. Mn1 (Mn1). We purified the Mn(II)-oxidizing enzyme from intracellular extracts of Mn1. The enzyme oxidized Mn(II) most effectively at pH 7.0 and 45 °C. The N-terminal amino acid sequence of the purified enzyme possessed homology with multicopper oxidases in fungi. The properties of the enzyme and the effects of the pH and inhibitors on the Mn(II)-oxidization activity suggested that the enzyme is a member of the multicopper oxidase family. The X-ray diffraction pattern of the BMOs produced by Mn1 showed a strong correlation with that of a typical poorly crystalized vernadite (δ-MnO2). Since BMOs are some of the most reactive materials in the environment, we investigated a potential new application of BMOs as oxidation catalysts. We confirmed that BMOs oxidized aromatic methyl groups when combined with the purified enzyme and a mediator, 1-hydroxybenzotriazole (HBT). BMO oxidation of 3,4-dimethoxytoluene achieved a better yield than that of abiotic MnO2 and white-rot fungus laccase under acidic and neutral pH conditions. Under neutral pH, the BMOs oxidized 3,4-dimethoxytoluene to yield 200-fold more 3,4-dimethoxybenzaldehyde than that of abiotic MnO2. This is the first report to reveal that BMOs combined with a Mn(II)-oxidizing enzyme and mediator can oxidize aromatic hydrocarbons to yield corresponding aldehydes.

Polyploid engineering by increasing mutant gene dosage in yeasts.

The yeast Saccharomyces cerevisiae, widely used for ethanol production, is one of the best-understood biological systems. Diploid strains of S. cerevisiae are preferred for industrial use due to the better fermentation efficiency, in terms of vitality and endurance as compared to those of haploid strains. Whole-genome duplications is known to promote adaptive mutations in microorganisms, and allelic variations considerably contribute to the product composition in ethanol fermentation. Although fermentation can be regulated using various strains of yeast, it is quite difficult to make fine adjustment of each component in final products. In this study, we demonstrate the use of polyploids with varying gene dosage (the number of copies of a particular gene present in a genome) in the regulation of ethanol fermentation. Ethyl caproate is one of the major flavouring agents in a Japanese alcoholic beverage called sake. A point mutation in FAS2 encoding the α subunit of fatty acid synthetase induces an increase in the amount of caproic acid, a precursor of ethyl caproate. Using the FAS2 as a model, we generated and evaluated yeast strains with varying mutant gene dosage. We demonstrated the possibility to increase mutant gene dosage via loss of heterozygosity in diploid and tetraploid strains. Productivity of ethyl caproate gradually increased with mutant gene dosage among tetraploid strains. This approach can potentially be applied to a variety of yeast strain development via growth-based screening.

[A Case of Renal Epithelioid Angiomyolipoma with Recurrence in the Abdominal Cavity].

A 37-year-old man with no symptoms or family history of tuberous sclerosis complex presented to our hospital with abdominal pain in 2013. Abdominal computed tomography (CT) revealed a rupture in the right renal angiomyolipoma (AML) having a maximum diameter of 7 cm. He had undergone a transarterial embolization. Follow-up CT showed an increase in the size of the right tumor to 11 cm, and therefore, right nephrectomy was performed in 2016. The diagnosis of epithelioid AML (EAML) was confirmed. In 2019, he was diagnosed with a solitary tumor near right-sided transverse colon, which was resected and showed recurrence of EAML. He was disease-free 6 months after surgery. EAML has malignant potential, with 30-50% of reported EAML cases resulting in local recurrence or distant metastasis. Previous recurrence or metastasis may occur 0.25-12 years postoperatively. Furthermore, multiple and unresectable recurrences or metastases, arising early in the postoperative period may lead to a poor outcome. Therefore, close and long-term follow-up is required.

[Clinical Effect of Nivolumab on Advanced Renal Cell Carcinoma with Peritoneal Metastasis].

Peritoneal dissemination or metastasis is a relatively rare presentation of renal cell carcinoma. We report four cases of advanced renal cell carcinoma with peritoneal metastases treated with nivolumab. Three cases showed an objective response in the metastatic lesions including peritoneal sites. After nivolumab administration, the computed tomography scan showed a transient enlargement of peritoneal lesions in two cases, which could be considered as pseudoprogression. Temporal changes of neutrophil-tolymphocyte ratio, C-reactive protein, and eosinophil ratio during the clinical course reflected the treatment effect of nivolumab in these patients, indicating that these could be potential biomarkers of the response. To our knowledge, this is the first case series showing therapeutic activity of nivolumab against peritoneal metastases in patients with renal cell carcinoma.

Efficacy and Safety of Carboplatin Plus Paclitaxel as the First-, Second-, and Third-line Chemotherapy in Men With Castration-resistant Prostate Cancer.

INTRODUCTION: Carboplatin and paclitaxel (CP) had shown moderate efficacy in treating castration-resistant prostate cancer (CRPC) before standard first-line docetaxel chemotherapy became available. Currently, for patients with homology-directed repair gene defects as well as for unselected patients, platinum chemotherapy is administered after all standard treatments have been ineffective. Here, we retrospectively studied the efficacy and safety of CP administered as the first-, second-, and third-line chemotherapy in patients with CRPC. PATIENTS AND METHODS: A retrospective chart review was performed for 58 patients with CRPC who received CP between 2001 and 2018 in a single institution. Twenty-seven patients received CP as the first-line chemotherapy, 21 as the second-line after docetaxel, and 10 as the third-line after docetaxel and cabazitaxel. Prostate-specific antigen (PSA) responses (> 50% decline of PSA from baseline), progression-free survival, overall survival, and adverse events were examined. RESULTS: PSA responses at any time were 55.6%, 19.0%, and 10.0%; PSA responses at 12 weeks were 48.1%, 14.3%, and 10.0%; the median progression-free survival was 3, 1, and 1 month; and the median overall survival was 19, 11, and 6 months, respectively, for the first-, second-, and third-line settings. The only patient who achieved exceptional and durable PSA response in the third-line setting had a deleterious germline BRCA2 mutation (5645C>A). The adverse event profile was favorable. CONCLUSION: CP shows moderate efficacy against CRPC in the first-line setting, but shows little effect in the third-line setting. CP after docetaxel and cabazitaxel may be recommended in selected patients with CRPC with homology-directed repair gene defects.

[A Case of Late Onset Nivolumab-Induced Interstitial Nephritis in a Patient with Metastatic Renal Cell Carcinoma].

A 43-year-old man underwent nephrectomy for right renal cell carcinoma (cT3aN0M1 (PUL), clear cell carcinoma). Thereafter, he was treated with sunitinib for lung metastases as the first-line therapy for three months. Because lung metastases progressed and new bone metastases appeared, nivolumab was started for the second-line treatment. Although the cancer progression was suppressed by multidisciplinary treatment combined with systemic immunotherapy and local radiation therapy, he developed severe acute kidney injury with cortical swelling after eighteen months of nivolumab treatment. A diagnosis of acute interstitial nephritis induced by nivolumab was made based on biopsy findings. Treatment with prednisolone (1.0 mg/kg daily) led to a rapid improvement in renal function. We must consider the possibility of immunerelated adverse events, especially nivolumab-induced acute kidney injury, even after long-term treatment.

A note on retrograde gene transfer efficiency and inflammatory response of lentiviral vectors pseudotyped with FuG-E vs. FuG-B2 glycoproteins.

Pseudotyped lentiviral vectors give access to pathway-selective gene manipulation via retrograde transfer. Two types of such lentiviral vectors have been developed. One is the so-called NeuRet vector pseudotyped with fusion glycoprotein type E, which preferentially transduces neurons. The other is the so-called HiRet vector pseudotyped with fusion glycoprotein type B2, which permits gene transfer into both neurons and glial cells at the injection site. Although these vectors have been applied in many studies investigating neural network functions, it remains unclear which vector is more appropriate for retrograde gene delivery in the brain. To compare the gene transfer efficiency and inflammatory response of the NeuRet vs. HiRet vectors, each vector was injected into the striatum in macaque monkeys, common marmosets, and rats. It was revealed that retrograde gene delivery of the NeuRet vector was equal to or greater than that of the HiRet vector. Furthermore, inflammation characterized by microglial and lymphocytic infiltration occurred when the HiRet vector, but not the NeuRet vector, was injected into the primate brain. The present results indicate that the NeuRet vector is more suitable than the HiRet vector for retrograde gene transfer in the primate and rodent brains.

Association of Missense Polymorphism in HSD3B1 With Outcomes Among Men With Prostate Cancer Treated With Androgen-Deprivation Therapy or Abiraterone.

Importance: Recently, genetic polymorphism in HSD3B1 encoding 3ß-hydroxysteroid dehydrogenase-1 has been shown to be associated with oncological outcome when treated with androgen-deprivation therapy (ADT) for prostate cancer. Upfront abiraterone combined with ADT has proved survival benefit. However, its effect on oncological outcome among different ethnicities and in abiraterone treatment remain unclear. Objective: To investigate the significance of missense polymorphism in HSD3B1 gene among men treated with primary ADT or abiraterone. Design, Setting, and Participants: This prognostic study included Japanese patients with metastatic hormone-sensitive prostate cancer between June 1993 and July 2005 and with castration-resistant prostate cancer between September 2014 and February 2018. Genome DNA was obtained from patient whole blood samples, and genotyping on HSD3B1 (rs1047303, 1245C) was performed by Sanger sequencing. Exposures: Primary ADT for metastatic hormone-sensitive prostate cancer and abiraterone for castration-resistant prostate cancer. Main Outcomes and Measures: The association of genotype in HSD3B1 with clinicopathological parameters and oncological outcome, including prostate-specific antigen response, progression-free survival, treatment failure-free survival, and overall survival was examined. Results: Of 203 men, 104 were in the primary ADT cohort (median [interquartile range] age, 72 [67-76] years) and 99 men were in the abiraterone group (median [interquartile range] age, 74 [67-80] years). Most patients carried metastatic lesions in each cohort. Among the cohort of primary ADT, men carrying heterozygous and homozygous variant types in HSD3B1 gene showed higher progression risk (hazard ratio [HR], 2.34; 95% CI, 1.08-4.49; P = .03) but not any-caused death risk (HR, 1.36; 95% CI, 0.52-2.92; P = .50), compared with men carrying homozygous wild type. In contrast, among the abiraterone cohort, men carrying variant type in HSD3B1 gene showed lower progression risk (HR, 0.32; 95% CI, 0.12-0.69; P = .006) and lower all-cause mortality risk (HR, 0.40; 95% CI, 0.13-0.94; P = .04) compared with men carrying homozygous wild type. Conclusions and Relevance: This study showed that HSD3B1 genetic variant is distinctly associated with oncological outcome between primary ADT and abiraterone in Japanese men, suggesting universal significance among different ethnicities in primary ADT, as well as promise as a predictive biomarker of ADT and abiraterone.

Bowel perforation by a peritoneal dialysis catheter: report of two cases.

BACKGROUND: Complications of peritoneal dialysis (PD) such as pain and catheter leakage are frequently reported. Delayed bowel perforation of a PD catheter is a rare adverse event but a serious complication associated with significant mortality. Bowel perforation of a PD catheter is difficult to differentiate from PD-related peritonitis and likely to result in a delay in diagnosis. Here, we report two cases of bowel perforation after PD catheter insertion by the stepwise initiation of PD using the Moncrief and Popovich technique (SMAP) and peritoneal wall anchor technique (PWAT). CASE PRESENTATION: The first case was a 53-year-old woman with end-stage renal disease (ESRD) due to diabetic nephropathy and a history of entero-adhesiolysis. She underwent PD catheter insertion by the SMAP with PWAT. Four months after PD catheter insertion, the catheter was found to perforate sigmoid colon. The second case was a 57-year-old woman with ESRD due to large polycystic kidney disease. She underwent the same procedure. After exteriorization of the catheter, she developed peritonitis due to perforation of the catheter tip into the bowel. Both patients were safely removed the catheter with uneventful recovery. CONCLUSION: We reported two cases of a rare complication of PD catheter. The SMAP method, PWAT, enlarged kidneys and migration of the lower cuff may be risk factors of bowel perforation of a PD catheter.