Metastasizing aneurysmal dermatofibroma initially diagnosed as angiosarcoma confirmed by CD63::PRKCD fusion gene detection with nanopore sequencing.

Dermatofibroma (DF) is a benign tumor that forms pedunculated lesions ranging in size from a few millimeters to 2 cm, usually affecting the extremities and trunks of young adults. Histopathologically, DF is characterized by the storiform proliferation of monomorphic fibroblast-like spindle cells. In addition to neoplastic cells, secondary elements such as foamy histiocytes, Touton-type giant cells, lymphoplasmacytes, and epidermal hyperplasia are characteristic histological features. Several histological variants, including atypical, cellular, aneurysmal, and lipidized variants, have been reported; cases with variant histologies are sometimes misdiagnosed as sarcomas. We present a case of metastasizing aneurysmal DF that was initially diagnosed as an angiosarcoma on biopsy. A 26-year-old woman was referred to our hospital with a gradually enlarging subcutaneous mass in her lower left leg. Positron emission tomography-computed tomography revealed high fluorodeoxyglucose uptake not only in the tumor but also in the left inguinal region. On biopsy, ERG and CD31-positive atypical spindle cells proliferated in slit-like spaces with extravasation, leading to the diagnosis of angiosarcoma. Histology of the wide-resection specimen was consistent with DF, and lymph node metastasis was also observed. Nanopore DNA sequencing detected CD63::PRKCD fusion and copy number gain, although CD63 was not included in the target region of adaptive sampling. This report highlights the importance of recognizing the unusual clinical, radiological, and pathological features of DF to avoid misdiagnosis, and the potential diagnostic utility of nanopore sequencer.

Establishment and characterization of multiple patient-derived organoids from a case of advanced endometrial cancer.

Patient-derived organoids (PDOs) retain the original tumor's characteristics to a large degree and allow direct evaluation of the drug sensitivity, thereby emerging as a valuable resource for both basic and preclinical researches. Whereas most past studies stereotypically adopted a single PDO as an avatar of the patient, it remains to be investigated whether this assumption can be justified even for the tumor with spatial diversity. To address this issue, we established and characterized multiple PDOs originating from various sites of a patient with advanced uterine carcinosarcoma (UCS). Specifically, cancer cells were separately sampled from three sites; resected UCS tumor tissue, the peritoneal lavage fluid, and an intra-uterine brushing of the tumor. The three derived PDOs were morphologically undistinguishable, displaying typical carcinoma organoids-like appearance, but two of them proliferated at a faster rate. The primary tumor harbored mutations in TP53 and STK11 along with amplifications in CCNE1, ERBB2, and KRAS. These two mutations and the CCNE1 amplification were detected in all PDOs, while either KRAS or ERBB2 amplification was selectively observed in each PDO in a mutually exclusive manner. Observed intra-tumor heterogeneity in HER2 expression was differentially reproduced in the PDOs, which mirrored each PDO's sensitivity to HER2 inhibitors. Inter-PDO heterogeneity was also evident in sensitivity to standard cytotoxic agents. Lastly, a drug screening identified four candidate reagents commonly effective to all PDOs. Collectively, we showed that multiple PDOs could help reproduce the spatial diversity of a tumor and serve as a valuable resource in UCS research in many respects.

The diagnostic utility of cytology specimen in a case of EWSR1::NFATC2 sarcoma.

EWSR1::NFATC2 sarcoma, a rare round cell sarcoma constituting the majority of EWSR1::non-ETS sarcomas, has recently been defined in the latest WHO classification. To date, the cytological findings of EWSR1::NFATC2 sarcoma remain undocumented. We present the case of a 25-year-old man with a history of polyostotic fibrous dysplasia in the right leg, referred to our hospital with left thigh pain. Cytological findings included metachromasia, minimally pleomorphic round cells, and eosinophilic infiltration. There was no precursor fibrous dysplasia and the initial diagnosis was undifferentiated pleomorphic sarcoma. Following histologic review, we successfully performed immunocytochemistry and fluorescence in situ hybridization (FISH) on archival cytology specimens. The tumor cells were positive for NKX2-2, NKX3-1, and PAX7 and showed amplified 5' single signals of EWSR1 gene. Reverse transcriptase-polymerase chain reaction revealed an in-frame fusion of EWSR1 and NFATC2. This report describes the cytological features of EWSR1::NFATC2 sarcoma and highlights the diagnostic utility of archival cytology specimens.

Immunologic Significance of CD80/CD86 or Major Histocompatibility Complex-II Expression in Thymic Epithelial Tumors.

Introduction: Unresectable or recurrent thymic epithelial tumors (TETs) have a poor prognosis, and treatment options are limited. This study aimed to investigate the immunologic significance of CD80/CD86 or major histocompatibility complex class II (MHC-II) expression in TETs, as potential predictive biomarkers for immune checkpoint inhibitors (ICIs). Methods: We analyzed CD80, CD86, MHC class I (MHC-I), and MHC-II expression in TETs using immunohistochemistry and investigated their association with T-cell infiltration or ICI efficacy. In addition, we generated CD80- or MHC-II-expressing mouse tumors, evaluated the effects of ICIs, and analyzed tumor-infiltrating lymphocytes. We also performed tumor-rechallenge experiments in vivo. Results: We found that approximately 50% and 30% of TETs had high expression of CD80/CD86 and MHC-II in tumor cells, respectively, and that this expression was related to T-cell infiltration in clinical samples. In mouse models, both CD80 and MHC-II increase the effects of ICIs. In addition, senescent T cells and long-lived memory precursor effector T cells were significantly decreased and increased, respectively, in tumor-infiltrating lymphocytes from CD80-expressing tumors, and rechallenged tumors were completely rejected after the initial eradication of CD80-expressing tumors by programmed cell death protein 1 blockade. Indeed, patients with CD80-high thymic carcinoma had longer progression-free survival with anti-programmed cell death protein 1 monoclonal antibody. Conclusions: Half of the TETs had high expression of CD80/CD86 or MHC-II with high T-cell infiltration. These molecules could potentially increase the effects of ICIs, particularly inducing a durable response. CD80/CD86 and MHC-II can be predictive biomarkers of ICIs in TETs, promoting the development of drugs for such TETs.

Multidisciplinary management for primary uterine osteosarcoma, including gene panel testing: case report and literature review.

Primary osteosarcoma of the uterus (uOS) is rare, and its standard treatment has not yet been established. Herein, we present the case of a 50-year-old woman with uOS who demonstrated an improved prognosis after multiple surgeries to the metastatic sites. After the initial diagnosis of uOS, the patient showed recurrence and distant metastasis and hence expected to exhibit a poor prognosis. The patient underwent multiple surgical resections of the metastatic as well as primary tumors, which enabled the patient to survive for 24 months after the initial surgery. Considering that the median survival time of patients with uOS is approximately 6 months, the survival rate of our patient is noteworthy. Based on our observations, it is suggested that the resection of the primary and metastatic tumors might contribute to the extension of the survival period of the patient with chemo-resistant uOS.

Clinical Impact of Fine Needle Aspiration Cytology on Sentinel Node Biopsy after Preoperative Chemotherapy for Core Needle Biopsy-Proven Metastatic Lymph Nodes.

INTRODUCTION: Sentinel node biopsy (SNB) has been increasingly performed for patients with lymph node (LN)-positive (cN1) breast cancer that converted to LN-negative (ycN0) status after neoadjuvant chemotherapy (NAC). This study aimed to clarify the SNB avoidance rates using fine needle aspiration cytology (FNAC) for metastatic LNs after NAC. METHODS: This study included 68 patients with cN1 breast cancer undergoing NAC from April 2019 to August 2021. Patients with biopsy-proven metastatic clip-marked LNs (clipped LNs) underwent eight cycles of NAC. Ultrasonography (US) was performed to evaluate the effect of the treatment on the clipped LNs, and FNAC was performed after NAC. Patients with ycN0 status determined using FNAC underwent SNB. Those with positive results for FNAC or SNB underwent axillary LN dissection. Histopathology results and FNA were compared for clipped LNs after NAC. RESULTS: Of the 68 cases, 53 were ycN0 and 15 were clinically positive LNs after NAC (ycN1) on US. Further, 13% (7/53) of all ycN0 and 60% (9/15) of all ycN1 cases showed residual metastasis in the LNs on FNAC. CONCLUSION: FNAC was diagnostically useful for patients with ycN0 status on US imaging. Using FNAC for LNs after NAC helped avoid unnecessary SNB in 13% of the cases.

Derivation of pancreatic acinar cell carcinoma cell line HS-1 as a patient-derived tumor organoid.

Acinar cell carcinoma (ACC) of the pancreas is a malignant tumor of the exocrine cell lineage with a poor prognosis. Due to its rare incidence and technical difficulties, few authentic human cell lines are currently available, hampering detailed investigations of ACC. Therefore, we applied the organoid culture technique to various types of specimens, such as bile, biopsy, and resected tumor, obtained from a single ACC patient. Despite the initial propagation, none of these organoids achieved long-term proliferation or tolerated cryopreservation, confirming the challenging nature of establishing ACC cell lines. Nevertheless, the biopsy-derived early passage organoid developed subcutaneous tumors in immunodeficient mice. The xenograft tumor histologically resembled the original tumor and gave rise to infinitely propagating organoids with solid features and high levels of trypsin secretion. Moreover, the organoid stained positive for carboxylic ester hydrolase, a specific ACC marker, but negative for the duct cell marker CD133 and the endocrine lineage marker synaptophysin. Hence, we concluded the derivation of a novel ACC cell line of the pure exocrine lineage, designated HS-1. Genomic analysis revealed extensive copy number alterations and mutations in EP400 in the original tumor, which were enriched in primary organoids. HS-1 displayed homozygous deletion of CDKN2A, which might underlie xenograft formation from organoids. Although resistant to standard cytotoxic agents, the cell line was highly sensitive to the proteasome inhibitor bortezomib, as revealed by an in vitro drug screen and in vivo validation. In summary, we document a novel ACC cell line, which could be useful for ACC studies in the future.

Transcriptomic analysis reveals high ITGB1 expression as a predictor for poor prognosis of pancreatic cancer.

Transcriptomic analysis of cancer samples helps identify the mechanism and molecular markers of cancer. However, transcriptomic analyses of pancreatic cancer from the Japanese population are lacking. Hence, in this study, we performed RNA sequencing of fresh and frozen pancreatic cancer tissues from 12 Japanese patients to identify genes critical for the clinical pathology of pancreatic cancer among the Japanese population. Additionally, we performed immunostaining of 107 pancreatic cancer samples to verify the results of RNA sequencing. Bioinformatics analysis of RNA sequencing data identified ITGB1 (Integrin beta 1) as an important gene for pancreatic cancer metastasis, progression, and prognosis. ITGB1 expression was verified using immunostaining. The results of RNA sequencing and immunostaining showed a significant correlation (r = 0.552, p = 0.118) in ITGB1 expression. Moreover, the ITGB1 high-expression group was associated with a significantly worse prognosis (p = 0.035) and recurrence rate (p = 0.028). We believe that ITGB1 may be used as a drug target for pancreatic cancer in the future.

Machine learning with imaging features to predict the expression of ITGAV, which is a poor prognostic factor derived from transcriptome analysis in pancreatic cancer.

Radiogenomics has attracted attention for predicting the molecular biological characteristics of tumors from clinical images, which are originally a collection of numerical values, such as computed tomography (CT) scans. A prediction model using genetic information is constructed using thousands of image features extracted and calculated from these numerical values. In the present study, RNA sequencing of pancreatic ductal adenocarcinoma (PDAC) tissues from 12 patients was performed to identify genes useful in evaluating clinical pathology, and 107 PDAC samples were immunostained to verify the obtained findings. In addition, radiogenomics analysis of gene expression was performed by machine learning using CT images and constructed prediction models. Bioinformatics analysis of RNA sequencing data identified integrin αV (ITGAV) as being important for clinicopathological factors, such as metastasis and prognosis, and the results of sequencing and immunostaining demonstrated a significant correlation (r=0.625, P=0.039). Notably, the ITGAV high­expression group was associated with a significantly worse prognosis (P=0.005) and recurrence rate (P=0.003) compared with the low­expression group. The ITGAV prediction model showed some detectability (AUC=0.697), and the predicted ITGAV high­expression group was also associated with a worse prognosis (P=0.048). In conclusion, radiogenomics predicted the expression of ITGAV in pancreatic cancer, as well as the prognosis.

Treatment Strategy for Patients with HR-Positive HER2-Negative Metastatic Breast Cancer That Progressed on CDK4/6 Inhibitors.

Background/Aims: The study aim was to evaluate if mTOR inhibitors can be considered as a treatment option for HR+ HER2- metastatic breast cancer (MBC) after progression on CDK4/6 inhibitors in clinical practice. Methods: We retrospectively collected the clinicopathological data of patients with HR+ HER2- MBC treated with CDK4/6 inhibitors and subsequent therapies at our institution between 2014 and 2020. The patients were divided into 3 groups according to the type of subsequent treatment: (A) exemestane plus everolimus, (B) endocrine monotherapy, and (C) chemotherapy. Overall survival (OS) was estimated by using the Kaplan-Meier method and compared by using the log-rank test. The efficacy and adverse events (AEs) of each subsequent treatment were assessed by using Fisher's exact tests. Results: Eighty-six patients (34 in group A, 20 in group B, 32 in group C) were included. The most common endocrine therapy in group B was fulvestrant (40%). The major chemotherapy regimen in group C was eribulin (25%). The median OS times after stopping CDK4/6 inhibitors were 34.5 months (95% confidence interval, 17.2 to NA), 13.6 months (3.9 to NA), and 19.5 months (18.8 to NA) in group A, group B, and group C, respectively. The only significant difference in OS was observed between group A and group B (20.9 months; p = 0.003). There was no difference in the incidence of grade 3 AEs between groups A and C or in the frequency of treatment discontinuation because of AEs among the 3 groups. Conclusion: Our study shows that mTOR inhibitors might be an effective treatment option for patients with HR+ HER2- MBC previously treated with CDK4/6 inhibitors.

Prediction of the differences in tumor mutation burden between primary and metastatic lesions by radiogenomics.

Tumor mutational burden (TMB) is gaining attention as a biomarker for responses to immune checkpoint inhibitors in cancer patients. In this study, we evaluated the status of TMB in primary and liver metastatic lesions in patients with colorectal cancer (CRC). In addition, the status of TMB in primary and liver metastatic lesions was inferred by radiogenomics on the basis of computed tomography (CT) images. The study population included 24 CRC patients with liver metastases. DNA was extracted from primary and liver metastatic lesions obtained from the patients and TMB values were evaluated by next-generation sequencing. The TMB value was considered high when it equaled to or exceeded 10/100 Mb. Radiogenomic analysis of TMB was performed by machine learning using CT images and the construction of prediction models. In 7 out of 24 patients (29.2%), the TMB status differed between the primary and liver metastatic lesions. Radiogenomic analysis was performed to predict whether TMB status was high or low. The maximum values for the area under the receiver operating characteristic curve were 0.732 and 0.812 for primary CRC and CRC with liver metastasis, respectively. The sensitivity, specificity, and accuracy of the constructed models for TMB status discordance were 0.857, 0.600, and 0.682, respectively. Our results suggested that accurate inference of the TMB status is possible using radiogenomics. Therefore, radiogenomics could facilitate the diagnosis, treatment, and prognosis of patients with CRC in the clinical setting.

Synchronous early-stage breast cancer and axillary follicular lymphoma diagnosed by core needle biopsy: A case report.

Synchronous double cancers are an infrequent finding. The focus of this study was a case of diagnosed synchronous double breast cancer (BC) and axillary (Ax) follicular lymphoma (FL). The patient was a 73-year-old woman who had been visiting her local doctor for follow-up of a fibroadenoma of the left breast, and was referred to our hospital after being diagnosed with invasive ductal carcinoma (IDC) of the left breast. Ultrasonography (US) revealed enlarged Ax lymph nodes (LNs) and US-guided core needle biopsy (CNB) was performed. CNB revealed no metastasis of IDC; however, a diagnosis of FL was made. Therefore, the patient was diagnosed with synchronous double BC and Ax FL and underwent partial surgical resection of the BC and close monitoring of the FL. To the best of our knowledge, this is the first case of malignant lymphoma diagnosed by CNB of Ax LNs during preoperative BC screening. CNB allows for a shorter waiting time for the examination, and it is considered to be minimally invasive, cost-effective and non-inferior to surgical resection in terms of specimen volume. Therefore, active preoperative evaluation of Ax LNs using US-guided CNB may contribute to BC staging, and may also help diagnose synchronous cancers.

Genetic subtype classification using a simplified algorithm and mutational characteristics of diffuse large B-cell lymphoma in a Japanese cohort.

Recent large-scale genetic studies have proposed a new genetic classification of diffuse large B-cell lymphoma (DLBCL), which is clinically and biologically heterogeneous. However, the classification methods were complicated to be introduced into clinical practice. Here we retrospectively evaluated the mutational status and copy number changes of 144 genes in 177 Japanese patients with DLBCL, using targeted DNA sequencing. We developed a simplified algorithm for classifying four genetic subtypes-MYD88, NOTCH2, BCL2, and SGK1-by assessing alterations in 18 representative genes and BCL2 and BCL6 rearrangement status, integrating the significant genes from previous studies. In our cohort and another validation cohort from published data, the classification results in our algorithm showed close agreement with the other established algorithm. A differential prognosis among the four groups was observed. The NOTCH2 group showed a particularly poorer outcome than similar groups in previous reports. Furthermore, our study revealed unreported genetic features in the DLBCL subtypes that are mainly reported in Japanese patients, such as CD5-positive DLBCL and methotrexate-associated lymphoproliferative disorders. These results indicate the utility of our simplified method for DLBCL genetic subtype classification, which can facilitate the optimisation of treatment strategies. In addition, our study highlights the genetic features of Japanese patients with DLBCL.

CA19-9-producing esophageal adenocarcinoma originating from the esophageal cardia of the mid-thoracic esophagus: a case report.

BACKGROUND: Although there are many studies on primary esophageal adenocarcinoma arising from Barrett's esophagus or ectopic gastric mucosa, reports on adenocarcinoma arising from esophageal cardiac glands are extremely rare. Herein, we report a case of mid-thoracic cancer antigen 19-9 (CA 19-9)-producing primary esophageal adenocarcinoma, which presumably originated from the cardiac glands. CASE PRESENTATION: A 74-year-old man was referred to our department with advanced esophageal cancer, which initially presented with dyspepsia. Serum levels of cancer antigen 19-9 (CA 19-9) were elevated (724.89 U/ml). Upper gastrointestinal endoscopy revealed a type 2 tumor on the posterior wall of the mid-thoracic esophagus approximately 29-32 cm from the incisor. Mucosal biopsy was consistent with a diagnosis of adenocarcinoma. Contrast-enhanced computed tomography showed a circumferential wall thickening in the mid-thoracic esophagus without enlarged lymph nodes or distant metastasis. Positron emission tomography-computed tomography showed accumulation in the primary tumor, but no evidence of lymph node or distant metastasis. According to these findings, the adenocarcinoma was staged as cT3N0M0, thereby, requiring subtotal esophagectomy with lymph node dissection. Postoperative course was uneventful. Histopathologic analysis revealed a 50 × 40 mm moderately differentiated adenocarcinoma with invasion to the thoracic duct and lymph node metastasis at #108(1/4), #109R(1/3), and #109L(1/3). After surgery, the stage was revised to moderately differentiated pT4apN2pM0 (pStage III). Immunostaining revealed expression of CA19-9 and suggested esophageal cardiac gland origin of the tumor. Three months after the surgery, the patient showed no recurrence and is undergoing outpatient observation. CONCLUSIONS: We experienced a case of mid-thoracic CA19-9-producing primary esophageal adenocarcinoma, which was presumed to have originated in the esophageal cardiac glands. Due to the scarcity of studies regarding this condition, specific management needs to be further clarified.

Surgical resection of undifferentiated pleomorphic sarcoma (UPS) with jejunal perforation, a suspected case of metastasis of lung cancer.

Undifferentiated pleomorphic sarcoma (UPS) in the gastrointestinal tract is rare. According to the diagnostic criteria after the World Health Organization 2013 reclassification, there has been only one case of UPS with perforation of the gastrointestinal tract. A 71-year-old man who was undergoing outpatient chemotherapy at the department of respiratory medicine of our hospital for lung cancer and brain metastasis, was admitted to our hospital with sudden high fever and abdominal pain. A computed tomography scan showed free air in the abdominal cavity with thickening of part of the jejunal wall. We suspected jejunal metastasis of lung cancer and performed emergency surgery for acute peritonitis due to gastrointestinal perforation in the same area. A Bormann type 2 tumour was found in the jejunum with perforation. The histopathological diagnosis was UPS. Ten months have passed since the surgery, and there has been no recurrence of UPS and no significant change in lung cancer. Primary UPS of the gastrointestinal tract is rare, and cases with perforation are extremely rare. Currently, ten months have passed since the surgery, and no recurrence has been observed. We encountered a case of UPS in which it was difficult to distinguish metastasis from lung cancer to the jejunum, and the emergency surgery gave us the chance to confirm the definitive diagnosis and save the patient's life.

Probing the tumorigenic potential of genetic interactions reconstituted in murine fallopian tube organoids.

Genetically engineered mice have been the gold standard in modeling tumor development. Recent studies have demonstrated that genetically engineered organoids can develop subcutaneous tumors in immunocompromised mice, at least for organs that prefer predominant driver mutations for tumorigenesis. To further substantiate this concept, the fallopian tube (FT), a major cell of origin of ovarian high-grade serous carcinoma (HGSC), which almost invariably carries TP53 mutations, was investigated for p53 inactivation-driven tumorigenesis. Murine FT organoids subjected to lentiviral Cre-mediated Trp53 deletion did not develop tumors. However, subsequent suppression of Pten and simultaneous induction of mutant Pik3ca led to the development of carcinoma in situ and HGSC-like tumors, respectively, whereas concurrent deletion of Apc resulted in the development of benign cysts, mirroring frequent activation of the PI3K/AKT axis and the marginal impact of Wnt pathway activation in HGSC. Consistent with the frequent activation of the RAS pathway in HGSC, mutant Kras cooperated with Trp53 deletion for the development of tumors, which unexpectedly contained sarcoma cells in addition to carcinoma cells, despite the epithelial origin of the inoculated organoids. This finding is in sharp contrast with the exclusive adenocarcinoma development from gastrointestinal organoids with the same genotype reported in previous studies, suggesting a tissue-specific epithelial-mesenchymal transition program. In tumor-derived organoids, the Cre-mediated recombination rate reached 100% for Trp53 but not for the other genes, highlighting the advantage of p53 inactivation in FT tumorigenesis. The Trp53 wildtype FT organoids expressing the mutant Kras developed sarcoma and carcinoma upon Cdkn2a suppression and Tgfbr2 deletion, respectively, revealing novel pro-tumorigenic genetic cooperation and critical roles of TGF-ß signaling for epithelial-mesenchymal transition in FT-derived tumorigenesis. Collectively, the organoid-based approach represents a shortcut to tumorigenesis and provides novel insights into the relationships among genotype, cell type, and tumor phenotype underlying tumorigenesis. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Kras activation in endometrial organoids drives cellular transformation and epithelial-mesenchymal transition.

KRAS, an oncogene, is frequently activated by mutations in many cancers. Kras-driven adenocarcinoma development in the lung, pancreas, and biliary tract has been extensively studied using gene targeting in mice. By taking the organoid- and allograft-based genetic approach to these organs, essentially the same results as in vivo models were obtained in terms of tumor development. To verify the applicability of this approach to other organs, we investigated whether the combination of Kras activation and Pten inactivation, which gives rise to endometrial tumors in mice, could transform murine endometrial organoids in the subcutis of immunodeficient mice. We found that in KrasG12D-expressing endometrial organoids, Pten knockdown did not confer tumorigenicity, but Cdkn2a knockdown or Trp53 deletion led to the development of carcinosarcoma (CS), a rare, aggressive tumor comprising both carcinoma and sarcoma. Although they originated from epithelial cells, some CS cells expressed both epithelial and mesenchymal markers. Upon inoculation in immunodeficient mice, tumor-derived round organoids developed carcinoma or CS, whereas spindle-shaped organoids formed monophasic sarcoma only, suggesting an irreversible epithelial-mesenchymal transition during the transformation of endometrial cells and progression. As commonly observed in mutant Kras-driven tumors, the deletion of the wild-type Kras allele was identified in most induced tumors, whereas some epithelial cells in CS-derived organoids were unexpectedly negative for KrasG12D. Collectively, we showed that the oncogenic potential of KrasG12D and the histological features of derived tumors are context-dependent and varies according to the organ type and experimental settings. Our findings provide novel insights into the mechanisms underlying tissue-specific Kras-driven tumorigenesis.

MCT4 is induced by metastasis-enhancing pathogenic mitochondrial NADH dehydrogenase gene mutations and can be a therapeutic target.

Pathogenic mitochondrial NADH dehydrogenase (ND) gene mutations enhance the invasion and metastasis of various cancer cells, and they are associated with metastasis in human non-small cell lung cancer (NSCLC). Moreover, monocarboxylate transporter 4 (MCT4) is overexpressed in solid cancers and plays a role in cancer cell proliferation and survival. Here, we report that MCT4 is exclusively expressed in mouse transmitochondrial cybrids with metastasis-enhancing pathogenic ND6 mutations. A high level of MCT4 is also detected in human NSCLC cell lines and tissues predicted to carry pathogenic ND mutations and is associated with poor prognosis in NSCLC patients. MCT4 expression in the cell lines is suppressed by N-acetyl-L-cysteine. Phosphatidylinositol-3 kinase (PI3K), AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) are involved in the regulation of MCT4 expression in the transmitochondrial cybrid cells. An MCT1/4 inhibitor effectively kills NSCLC cells with predicted pathogenic ND mutations, but an MCT1/2 inhibitor does not have the same effect. Thus, MCT4 expression is augmented by pathogenic ND mutations and could be a biomarker and a therapeutic target in pathogenic ND mutation-harbouring metastatic tumours.

CDK4 overexpression is a predictive biomarker for resistance to conventional chemotherapy in patients with osteosarcoma.

Osteosarcoma (OS) is the most common malignant bone tumor, and its sensitivity to preoperative chemotherapy is a significant prognostic factor. The present study aimed to identify potential genomic markers for the prediction of chemosensitivity in patients with OS using a genomic approach. A total of 50 pediatric and adolescent patients diagnosed with high­grade OS were selected. Each pre­therapeutic biopsy sample was subjected to comparative genomic hybridization array analysis and targeted exome sequencing. Although no recurrent gene mutation was observed in chemoresistant tumors, copy number analysis detected recurrent gain of chromosome 12q14.1, which was significantly more frequent (5/21; 24%) in the poor responder cohort than in the good responder cohort (0/29; 0%; P<0.01). Subsequent expression analysis revealed that CDK4 was the only gene in the 12q14.1 gained region with an expression level that was positively associated with copy number gains. In order to elucidate the effect of CDK4 on drug sensitivity, CDK4­overexpressing OS cell lines were treated with cisplatin (CDDP); significant attenuation of CDDP sensitivity, demonstrated by increased cell viability and decreased expression of cleaved caspase­9, was induced by enforced expression of CDK4. In addition, treatment with CDK4/6 inhibitor palbociclib in CDK4­overexpressing U2OS cells facilitated apoptosis and a significant decrease in cell viability in a dose­dependent manner. In conclusion, the results of the present study showed that higher expression and amplification of CDK4 in tumors is a predictive biomarker for resistance to conventional chemotherapy in patients with OS and that palbociclib is a promising drug for this therapeutically challenging cohort.