Body Composition and Clinical Outcomes in Esophageal Cancer Patients Treated with Immune Checkpoint Inhibitors.

BACKGROUND: Obesity is associated with increased mortality in various cancers, but the relationship between obesity and clinical outcomes in unresectable or recurrent esophageal cancer who receive immune checkpoint inhibitors (ICIs) remains unknown. This study investigated the association between body composition and clinical outcomes in patients with unresectable or recurrent esophageal cancer who received ICIs. METHODS: Utilizing an unbiased database of 111 unresectable or recurrent esophageal cancers, we evaluated the relationships between body composition (body mass index, waist circumference, psoas major muscle volume, and subcutaneous and visceral fat areas) at the initiation of ICI treatment and clinical outcomes including the disease control rate and progression-free survival (PFS). RESULTS: Waist circumference was significantly associated with the disease control rate at the first assessment (P = 0.0008). A high waist circumference was significantly associated with favorable PFS in patients treated with nivolumab. In an univariable model, for 5-cm increase of waist circumference in the outcome category of PFS, univariable hazard ratio (HR) was 0.73 (95% confidence interval [CI], 0.61-0.87; P = 0.0002). A multivariable model controlling for potential confounders yielded a similar finding (multivariable HR, 0.56; 95% CI, 0.33-0.94; P = 0.027). We observed the similar finding in esophageal cancer patients treated with pembrolizumab+CDDP+5-FU (P = 0.048). In addition, waist circumference was significantly associated with the prognostic nutritional index (P = 0.0073). CONCLUSIONS: A high waist circumference was associated with favorable clinical outcomes in ICI-treated patients with unresectable or recurrent esophageal cancer, providing a platform for further investigations on the relationships among body composition, nutrition, and the immune status.

The relationship between the treatment course and prognosis of oligometastasis after esophageal squamous cell carcinoma resection.

PURPOSE: The concept of oligometastasis, which represents limited metastatic disease, has recently gained interest, accompanied by a more detailed classification. This study aims to investigate the relationship between the treatment course and prognosis in patients with a recurrence of esophageal squamous cell carcinoma (ESCC) after curative esophagectomy. METHODS: 126 patients with ESCC recurrence after curative resection were enrolled in this study. Oligometastasis was defined as fewer than five recurrences in a single organ. Patients were classified as having oligometastatic recurrence (OLR) or polymetastatic recurrence (PLR). Patients were further classified into four subgroups according to lesion progression: persistent oligorecurrence (PER-OLR), converted polyrecurrence (CON-PLR), induced oligorecurrence (IND-OLR), and persistent polyrecurrence (PER-PLR). We analyzed the relationship between the recurrence patterns and prognosis according to the progression of oligometastatic lesions. RESULTS: OLR was identified in 58 (46%) of 126 patients with recurrence. Patients with OLR had a significantly better prognosis than those with PLR (P < 0.0001). A further subgroup analysis revealed that patients who underwent IND-OLR had a similar prognosis to those who underwent PER-OLR. CONCLUSIONS: This study suggests that OLR is a prognostic factor after recurrence following resection of ESCC and that PLR can be converted to OLR by therapeutic intervention to achieve a long-term survival.

Textbook outcome contributes to long-term prognosis in older adults with gastric cancer.

PURPOSE: Textbook outcome (TO) is a composite quality measurement of short-term outcomes for evaluating surgical procedures. We investigated whether TO can be used to predict outcomes after curative gastric cancer (GC) surgery in older adults. METHODS: We retrospectively analyzed 492 consecutive patients who underwent curative gastrectomy for GC from 2005 to 2017. Among these, 141 advanced-age patients were eligible. The patients were divided into two groups: those who achieved TO (a-TO group) and those who failed to achieve TO (f-TO group). In accordance with previous reports, TO consisted of eight metrics. We evaluated the association between TO and long-term survival. RESULTS: TO was achieved 73 (52%) patients. The patients in the f-TO group had a significantly higher body mass index (P = 0.01), longer surgery time (P = 0.03), and more blood loss (P = 0.001). The metric with the lowest achievement rate was "no postoperative severe complication." The patients in the f-TO group had significantly shorter overall survival than those in the a-TO group (P = 0.03). Multivariable Cox regression analyses of overall survival revealed that an American Society of Anesthesiologists physical status classification of 3 (hazard ratio [HR], 3.28; 95% confidence interval [CI], 1.79-5.98; P < 0.0001) and f-TO (HR, 1.92; 95% CI, 1.09-3.39; P = 0.02) were significantly associated with poor overall survival. CONCLUSION: TO can be used to predict outcomes after curative GC surgery in patients of advanced age.

Relationship between gut microbiome Fusobacterium nucleatum and LINE-1 methylation level in esophageal cancer.

BACKGROUND: We previously demonstrated the relationship of human microbiome Fusobacterium nucleatum with unfavorable clinical outcomes and inferior chemotherapeutic responses in esophageal cancer. Global DNA methylation is associated with the occurrence and development of various cancers. In our previous study, LINE-1 hypomethylation (i.e., global DNA hypomethylation) was associated with a poor prognosis in esophageal cancer. As the gut microbiota may play crucial roles in the DNA methylation of host cells, we hypothesized that F. nucleatum might influence LINE-1 methylation levels in esophageal cancer. METHODS: We qualified the F. nucleatum DNA using a quantitative PCR assay and LINE-1 methylation via a pyrosequencing assay using formalin-fixed paraffin-embedded specimens from 306 esophageal cancer patients. RESULTS: Intratumoral F. nucleatum DNA was detected in 65 cases (21.2%). The LINE-1 methylation scores ranged from 26.9 to 91.8 (median = 64.8) in tumors. F. nucleatum DNA was related to the LINE-1 hypomethylation of tumor lesions in esophageal cancer (P < 0.0001). The receiver operating characteristic curve analysis showed that the area under the curve was 0.71 for F. nucleatum positivity. Finally, we found that the impact of F. nucleatum on clinical outcomes was not modified by LINE-1 hypomethylation (P for interaction = 0.34). CONCLUSIONS: F. nucleatum alters genome-wide methylation levels in cancer cells, which may be one of the mechanisms by which F. nucleatum affects the malignant behavior of esophageal cancer.

Prognostic value of 18F-fluorodeoxyglucose uptake in the bone marrow on pretreatment positron emission tomography/computed tomography in patients with esophageal cancer who underwent esophagectomy.

BACKGROUND: Increased 18F-fluorodeoxyglucose (FDG) uptake in the bone marrow (BM) on positron emission tomography/computed tomography (PET/CT) clinically reflects increased BM metabolism owing to systemic inflammation, bacterial infection, anemia, and cytokine-producing tumors. The association between FDG uptake in the BM and prognosis after esophagectomy for esophageal cancer has not been investigated. METHODS: This study included 651 patients who underwent PET/CT before any treatment and McKeown esophagectomy for esophageal cancer between June 2007 and August 2021. The pretreatment degree of FDG uptake in the BM was evaluated using a visual assessment criterion. Patients were divided into low- and high-FDG uptake groups. We retrospectively investigated whether the degree of FDG uptake in the BM was associated with clinicopathological and surgical backgrounds, blood parameters, and prognosis. RESULTS: High FDG uptake in the BM was significantly associated with elevated white blood cell and neutrophil counts, increased C-reactive protein levels, decreased hemoglobin, serum albumin, and total cholesterol levels. High FDG uptake in the BM was an independent predictor of worse overall survival in clinical stages 0-II esophageal cancer (hazard ratio, 2.27; 95% confidence interval, 1.097-4.695; P = 0.027). Worse overall survival was also associated with advanced age, low American Society of Anesthesiologists physical status, an advanced clinical stage, and high intraoperative blood loss. CONCLUSION: Increased FDG uptake in the BM on pretreatment PET/CT may be a surrogate indicator of various clinically disadvantageous backgrounds and may act as a predictor of poor prognosis after esophageal cancer surgery.

Relationship between the severity of emphysematous change in the lung and morbidity after esophagectomy for esophageal cancer: A retrospective study on a novel strategy for risk prediction.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) prevalence increases post-esophagectomy morbidity. However, the association between COPD severity and post-esophagectomy morbidity remains unclear because of the lack of an objective method to classify COPD severity. Low attenuation volume ratio (LAVR) estimated using Ziostation2 may reflect the extent of emphysematous changes in the lungs and COPD severity, thereby predicting post-esophagectomy morbidity. METHODS: A total of 776 patients who underwent curative McKeown esophagectomy for esophageal cancer between April 2005 and June 2021 were included. The patients were divided into high and low preoperative LAVR groups. Short-term outcomes between the groups were compared for patients who underwent open esophagectomy (OE) and minimally invasive esophagectomy (MIE). RESULTS: A total of 219 (28%) patients were classified into the high LAVR group. High LAVR was significantly associated with disadvantageous patient characteristics such as advanced age, heavy smoking, and impaired respiratory function. Patients with high LAVR had a significantly higher incidence of severe morbidity and pneumonia after OE. High LAVR was an independent risk factor for severe morbidity (odds ratio [OR], 2.52; 95% confidence interval [CI]: 1.237-5.143; p = 0.011) and pneumonia (OR, 2.12; 95% CI: 1.003-4.493; p = 0.049) after OE. Meanwhile, LAVR was not correlated with the incidence of post-MIE morbidity. CONCLUSIONS: LAVR may reflect COPD severity and predict severe morbidity and pneumonia after OE, but not after MIE. Less invasiveness of MIE may alleviate the effects of various disadvantageous backgrounds associated with high LAVR on worse short-term outcomes.

Effect of SARS-CoV-2 BNT162b2 mRNA vaccine on thyroid autoimmunity: A twelve-month follow-up study.

Objectives: Graves' disease (GD) has been highlighted as a possible adverse effect of the respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccine. However, it is unknown if the SARS-CoV-2 vaccine disrupts thyroid autoimmunity. We aimed to present long-term follow-up of thyroid autoimmunity after the SARS-CoV-2 BNT162b2 mRNA vaccine. Methods: Serum samples collected from seventy Japanese healthcare workers at baseline, 32 weeks after the second dose (pre-third dose), and 4 weeks after the third dose of the vaccine were analyzed. The time courses of anti-SARS-CoV-2 spike immunoglobulin G (IgG) antibody, thyroid-stimulating hormone receptor antibody (TRAb), and thyroid function were evaluated. Anti-thyroglobulin antibodies (TgAb) and anti-thyroid peroxidase antibodies (TPOAb) were additionally evaluated in thirty-three participants. Results: The median age was 50 (IQR, 38-54) years and 69% were female. The median anti-spike IgG antibody titer was 17627 (IQR, 10898-24175) U/mL 4 weeks after the third dose. The mean TRAb was significantly increased from 0.81 (SD, 0.05) IU/L at baseline to 0.97 (SD, 0.30) IU/L 4 weeks after the third dose without functional changes. An increase in TRAb was positively associated with female sex (ß = 0.32, P = 0.008) and low basal FT4 (ß = -0.29, P = 0.02) and FT3 (ß = -0.33, P = 0.004). TgAb was increased by the third dose. Increase in TgAb was associated with history of the thyroid diseases (ß = 0.55, P <0.001). Conclusions: SARS-CoV-2 BNT162b2 mRNA vaccine can disrupt thyroid autoimmunity. Clinicians should consider the possibility that the SARS-CoV-2 vaccine may disrupt thyroid autoimmunity.

A case of clinical stage I gastric cancer with a schwannoma on the left supraclavicular fossa suspected as Virchow's node metastasis.

BACKGROUND: Gastric cancer is relatively prone to metastasis, although distant metastasis is rare during the early stage of disease. Here we report a rare case of schwannoma-associated Virchow metastasis of a patient with early-stage gastric cancer. CASE PRESENTATION: A 73-year-old man, diagnosed with early-stage gastric cancer, underwent preoperative scrutiny, and was only suspected to have Virchow metastasis. Owing to atypical metastatic findings, a lymph node biopsy was performed to confirm the diagnosis and to determine the treatment strategy. The pathology results of the biopsy showed a diagnosis of schwannoma, the patient was judged to be surgically resectable, and a laparoscopic gastrectomy was performed to achieve a radical resection. The patient is currently under outpatient observation with no apparent recurrence. CONCLUSION: Systemic chemotherapy is generally administered according to the physician's clinical judgment, although the results of a lymph node biopsy contribute to a more curative treatment. When nonspecific metastases are found, it is important to make a reliable diagnosis and to select a treatment that achieves a cure.

Immune-related adverse events and prognosis in patients with upper gastrointestinal cancer treated with nivolumab.

Background: Immune checkpoint inhibitors (ICIs) are increasingly being used for the treatment of upper gastrointestinal cancers [esophageal cancer and gastric cancer (GC)]. They cause imbalances in immunological tolerance, resulting in immune-related adverse events (irAEs). Although irAEs have been reported to be associated with the efficacy of ICIs in some cancers, the relationship between irAEs and prognosis of upper gastrointestinal cancers remains unknown. This study aimed to investigate the prognostic impact of irAEs in patients with advanced or recurrent upper gastrointestinal cancer treated with nivolumab. Methods: We retrospectively divided the patients (n=96) who received nivolumab into two groups: the irAEs group (n=41) and non-irAEs group (n=55), according to the Common Terminology Criteria for Adverse Events ver. 5.0. Results: irAEs were significantly associated with good performance status and high serum albumin levels (all P<0.05). The irAEs group had a significantly longer overall survival (OS) than the non-irAEs group [log-rank P=0.003; univariate hazard ratio (HR) =0.36, 95% confidence interval (CI) =0.21-0.65, P<0.01; multivariate HR =0.47, 95% CI =0.26-0.88, P=0.018]. Importantly, in both esophageal cancer and GC, the irAEs group experienced favorable clinical outcomes compared with the non-irAEs group. In the multivariate analysis, male sex (P<0.01), presence of irAEs (P=0.018), and good pretreatment performance status (P<0.01) were independent prognostic factors. Conclusions: Among patients with upper gastrointestinal cancer treated with nivolumab, the prognosis of patients who developed irAEs was better than that of patients who did not develop irAEs. Long-term continuation of nivolumab by early detection of irAEs and an appropriate response to irAEs are important.

Highly Advanced Colorectal Liver Metastases Successfully Treated With Fluorouracil Plus Leucovorin Monotherapy and Microwave Ablation.

BACKGROUND: Fluorouracil plus leucovorin (5-FU/LV) is a less toxic but mild chemotherapy. CASE REPORT: A 63-year-old male patient with rectal cancer and multiple colorectal liver metastases (CRLM, total volume of 1,826 ml) was hospitalized. He had several poor prognostic factors, including elevated levels of tumor markers, with carcinoembryonic antigen and carbohydrate antigen 19-9 levels of 17,119 ng/ml and 7,617 U/ml, respectively. Additionally, the patient had a low body mass index, poor performance status, and a history of apparent weight loss. After capecitabine and oxaliplatin for four cycles, 5-FU/LV has been lasting for nine months. Interestingly, tumor marker levels returned close to normal limits, and the total CRLM volume decreased to 154 ml without any enhancements. The patient's general condition clearly improved after a year of chemotherapy. CONCLUSION: Chemotherapy with 5-FU/LV and percutaneous microwave ablation is beneficial to achieve tumor control in patients with highly advanced liver-only CRLM and poor general condition.

Human Epidermal Growth Factor Receptor 2-positive Primary Adenocarcinoma in the Cervical Oesophagus: A Case Report.

BACKGROUND/AIM: Cervical oesophageal adenocarcinoma (COA) is extremely rare. We present a case of human epidermal growth factor receptor 2 (HER2)-positive COA that showed repeated recurrences despite multidisciplinary treatments. CASE REPORT: A 49-year-old male was diagnosed with clinical stage IVA COA that originated from ectopic gastric mucosa. He initially underwent definitive chemoradiotherapy (CRT) (60.0 Gy/30 fractions, 5-fluorouracil, and cisplatin). Two months after CRT, the right supraclavicular lymph node (LN) reenlarged and salvage lymphadenectomy was performed. Immunohistochemical staining revealed a HER2-positive adenocarcinoma. Four months after lymphadenectomy, multiple metastases in the mediastinal LNs and lungs were detected, and S-1, oxaliplatin and trastuzumab were administered. Four months after chemotherapy, the patient presented with new liver metastasis. Further metastasis was prevented by Nivolumab treatment for four months. CONCLUSION: HER2-positive COA may be more aggressive and may require further intensive treatments. This literature review may be helpful in determining treatment strategies for COA.

Laparoscopic Surgery for a Patient With Multiple Liver Metastases of Unknown Origin Concomitant With Gallbladder Tumor.

BACKGROUND: The liver is the digestive organ where metastatic adenocarcinoma of unknown primary site is most often observed. CASE REPORT: A 74-year-old man was diagnosed with a growing gallbladder tumor and multiple liver tumors limited to the left lateral sector. Liver tumors were suggested to be primary or secondary adenocarcinoma with no relation to the gallbladder tumor. Also for diagnostic purposes, laparoscopic full-thickness resection of the gallbladder, laparoscopic lateral sectionectomy and lymph node sampling were performed. The final histopathological diagnosis was hyperplastic polyp of the gallbladder and metastatic poorly differentiated adenocarcinoma of the liver. Liver tumors were suspected to originate from the stomach, duodenum, or small intestine; however, the primary sites could not be identified. The patient has been closely followed up without any chemotherapy 3 months after surgery. CONCLUSION: Laparoscopic surgery can be strongly recommended for patients with multiple liver tumors of unknown origin concomitant with a gallbladder tumor.

Far-advanced Colorectal Liver Metastases Successfully Managed With Modified ALPPS and Radiofrequency Ablation in Combination With Chemotherapy.

BACKGROUND: Large numbers of synchronous colorectal liver metastases are associated with poor prognosis. CASE REPORT: A 47-year-old male patient with rectal cancer and unresectable colorectal liver metastases (over 15 cm in diameter and over 30 metastases) was treated with a multidisciplinary treatment including systemic chemotherapy with mFOLFOX6/panitumumab and surgical therapies (colostomy, modified associating liver partition and portal vein ligation for staged hepatectomy together with radiofrequency ablation). For solitary recurrent colorectal liver metastases, percutaneous radiofrequency ablation with chemoembolization and open radiofrequency ablation in combination with the same systemic chemotherapy was performed. Since the diagnosis 3 years ago, he has been leading a good quality of life, free of any tumor or treatment. CONCLUSION: For patients with far-advanced but liver-only colorectal liver metastases, surgical therapy, systemic chemotherapy, and interventional treatment can be important for achieving good prognosis.

Intrahepatic Cholangiocarcinoma Coexisting With Multiple Bile Duct Adenoma Treated as Liver Metastasis from a Pancreatic Neuroendocrine Tumor.

BACKGROUND: Bile duct adenomas (BDA) may be precursor lesions of small duct-type, including mass-forming type intrahepatic cholangiocarcinoma (ICC). CASE REPORT: A 68-year-old woman was transferred to our facility for the treatment of a liver tumor, possibly metastasized from a pancreatic neuroendocrine tumor. Finally, two liver tumors were resected and histopathologically diagnosed as "BDA" and "ICC with a BDA-like component". In the BDA-like component, the MUC6 positive rate was notably lower and the Ki-67 positive rate was higher than the other BDAs and ICC component, respectively. The doubling time of the tumor volume in BDA was very long but was shortened (1,510 and 719 days). Distinct enlargement of the tumor and appearance of enhancement through diagnostic imaging was useful in diagnosing the transformation from a BDA to an ICC. CONCLUSION: An "adenoma-carcinoma sequence" may exist in the transformation process from a BDA to an ICC.

Theoretical study of the cycloaddition reaction of a tungsten-containing carbonyl ylide.

The [3+2] cycloaddition reaction of a tungsten-containing carbonyl ylide with methyl vinyl ether and the insertion reactions of the nonstabilized carbene complex intermediates produced have been investigated through the use of B3LYP density functional theory. The [3+2] cycloaddition reaction of the tungsten-containing carbonyl ylide has been proven to proceed concertedly, reversibly, and with high endo selectivity. The intermolecular Si-H insertion reactions of the carbene complex intermediates have been proven to be favored over the intramolecular C-H insertion, in good agreement with experimental results. Moreover, the kinetic endo/exo ratio of the [3+2] cycloaddition reaction has been shown to determine the endo/exo selectivity of the Si-H insertion products. In addition, secondary orbital interactions involving the benzene ring and the carbonyl ligand on the metal center have turned out to strongly influence the high endo selectivity of the [3+2] cycloaddition reaction with methyl vinyl ether.

Severe Encephalopathy, Lactic Acidosis and Hyperammonaemia With FOLFIRI Plus Aflibercept After Two-stage Hepatectomy: A Case Report.

BACKGROUND/AIM: Recent advances in chemotherapy have increased the possibility of conversion hepatectomy for patients with initially unresectable liver metastases. Although long-term chemotherapy and subsequent extensive hepatectomy are becoming more common, the toxicities of such chemotherapies are unclear. PATIENTS AND METHODS: We present a case report of a patient with metastatic colorectal cancer who developed severe encephalopathy with lactic acidosis and hyperammonaemia caused by 5-fluorouracil-based chemotherapy. Administration of vitamin B1 and continuous haemodiafiltration rapidly improved the patient's symptoms. CONCLUSION: Intensive treatment of metastatic colorectal cancer patients with 5-fluorouracil can induce rare adverse events.

[Management system of cancer chemotherapy regimens].

Cancer chemotherapy regimens which had been used at a ward and outpatient chemotherapy in various departments were collected and made available to everybody in October, 2003. However, it was difficult to manage cancer chemotherapy regimens in real time, from the viewpoint of risk management. Then, the Cancer Chemotherapy Center took the leading part and established a chemotherapy exploratory committee, which consists of 4 doctors, 2 nurses and 2 pharmacists, in June, 2006. The department of pharmacy could control all cancer chemotherapy regimens by this system, and lead the proper use of increasing anticancer agents. Inquiries on prescription by the pharmacist contributed to proper medical treatment. The role of the cancer chemotherapy exploratory committee and its outcome are described for the purpose of the prevention of medical accidents in this paper.

Three-Component Repurposed Technology for Enhanced Expression: Highly Accumulable Transcriptional Activators via Branched Tag Arrays.

In the past few years, several types of artificial transcriptional activator, based on CRISPR-Cas9, have been developed and refined. Of these, in synergistic activation mediator and SunTag systems, the effector proteins, expressed in trans, can be recruited to the target sites via the MS2 RNA-binding system and GCN4-scFv antibody system, respectively. Here, we report a strong transcriptional activation system achieved by fusing GCN4 repeat to MS2 coat protein to accumulate numbers of activators, fused to scFv antibodies. By targeting the CDH1 gene, we show that our novel system, named "TREE," results in a greater effect of activating exogenous reporter and endogenous gene. Moreover, by targeting another gene, RANKL, we consistently show the superiority of the TREE system with fewer single-guide RNAs compared to conventional systems. Our TREE system is a promising tool for transcriptional activation and can potentially contribute to other dCas9-mediated technologies such as epigenome editing and chromosome visualization.

[Does alpha1-blocker provide additional improvement of quality-of-life in patients with overactive bladder?--a multi-center prospective randomized trial between anti-cholinergic (propiverine chloride) with and without alpha1-blocker (urapidil)].

AIM: Storage/filling symptoms caused by overactive bladder (OAB) are bothersome to patients. The aim of this study is to clarify if alpha1-blocker provides additional benefit in combination with anticholinergic treatment in patients with OAB. METHODS: In total, 100 patients (men/women: 43/57, mean age: 71.3 years) who had frequency (more than eight times a day) and urgency (more than three times a week) were prospectively randomized, and allocated to two groups (monotherapy group [n = 52]: propiverine alone or combination group [n = 48]: propiverine plus urapidil). The primary end point was to compare the improvement of storage symptoms (numbers of frequency, urgency, disappearance of urge incontinence) as well as patients' quality of life (QOL) assessed by King's Health Questionnaires (KHQ) at baseline, 2 weeks, and 6 weeks after the start of treatment in both groups. The second end point was to evaluate the safety of these agents. RESULTS: Statistically significant improvements in terms of urgency and frequency were observed in both groups at two-weeks after the start of treatment as compared with baseline (p < 0.01 and < 0.05, respectively), while no inter-group difference was observed between the two groups. Significant improvement of QOL was observed after six weeks treatment in overall mean score, general health perception, incontinence impact, sleep/energy domains in both groups as compared with baseline. No significant difference was observed in terms of toxic events between the two groups. CONCLUSIONS: Although both groups showed identical improvement of storage symptoms and tolerability, no additional benefit of alpha1-blocker was observed.

Homeolog-specific targeted mutagenesis in Xenopus laevis using TALENs.

Transcription activator-like effector nucleases (TALENs) have previously been used for targeted genome editing in various organisms including Xenopus laevis. However, because of genomic polyploidization, X. laevis usually possess homeologous genes (homeologs) with quite similar sequences that make the analysis of gene function difficult. In the present study, we show methodological examples of targeted gene modification of X. laevis homeologs. The X. laevis cytoglobin gene (cygb) consists of two homeologs (xlcygba and xlcygbb), and molecular phylogenetic analysis suggested that they have potentially different functions. Thus, there is a need to establish a method of homeolog-specific gene disruption to clarify gene functions in detail. Here, we show successful examples of homeolog-specific and simultaneous gene disruption for xlcygba and xlcygbb. We found that selective digestion can be performed with at least three mismatches in TALEN target sites in both homeologs. This report paves the way for the functional analyses of X. laevis homeologs, even those containing nearly identical sequences.