Trifluridine and Tipiracil Hydrochloride Combination-Induced Interstitial Pneumonia: A Case Report.

We report a case of a 62-year-old male who was diagnosed with advanced rectal cancer. The attending gastro-enterologist initiated chemotherapy using capecitabine plus oxaliplatin and bevacizumab; however, this treatment regimen was discontinued, as the patient developed a skin rash. Once the skin rash improved, chemotherapy was re-initiated using a combination of trifluridine and tipiracil hydrochloride (TAS-102). The patient developed high fever and dyspnea 2 months after initiation of TAS-102. Chest high-resolution computed tomography showed bilateral diffuse ground glass opacities in all lung lobes with traction bronchiectasis. At this time, the gastro-enterologist consulted our department. The patient was put on non-invasive positive pressure ventilation due to worsening respiratory symptoms. The patient was suspected to develop TAS-102-induced interstitial pneumonia based on positive TAS-102 drug-induced lymphocyte stimulation test. The patient's respiratory symptoms and radiological findings improved after corticosteroid treatment. The corticosteroid dose was gradually decreased by 5 mg. Thereafter, chemotherapy was re-initiated using different anti-cancer agents.

Reconsidering the Cutoff Value for Sensitive and Refractory Relapses in Extensive-Stage SCLC in the Era of Immunotherapy.

INTRODUCTION: Traditionally, relapsed SCLC has been classified as "sensitive" or "refractory" on the basis of cutoff values (60 or 90 d) for the duration between the last chemotherapy and disease progression. Nevertheless, these cutoff values are not derived from rigorous analytical methods, and their applicability to contemporary treatments remains uncertain. METHODS: We conducted a retrospective multicenter study on patients with extensive-stage SCLC who underwent second-line therapy after platinum-doublet chemotherapy with or without immune checkpoint inhibitor (ICI) resistance before (pre-ICI cohort) and after (post-ICI cohort) approval of combination immunotherapy. We selected the optimal platinum-free interval cutoff value with the lowest two-sided p value in the multivariable Cox regression model for second-line overall survival. The internal validity of the chosen cutoff value was assessed using twofold cross-validation. RESULTS: There were 235 and 98 patients in the pre-ICI and post-ICI cohorts, respectively. In the pre-ICI cohort, the optimal cutoff was 59 days (p = 0.0001); the hazard ratio calculated using twofold cross-validation was 1.31 (95% confidence interval: 0.95-1.82]). In the post-ICI cohort, although the 60- and 90-day cutoff values could predict prognosis (60 d; p = 0.002, 90 d; p = 0.005), the optimal cutoff value was 75 days (p = 0.0002), which resulted in a median second-line overall survival of 15.9 and 5.0 months for patients with sensitive and refractory relapse, respectively (hazard ratio = 2.77, 95% confidence interval: 1.56-4.93). CONCLUSIONS: We clarified the previously ambiguous cutoff values for classifying relapsed SCLC and revealed that the 75-day cutoff most accurately predicts subsequent prognosis than the traditional cutoffs in the post-ICI era.

Liquid biopsy detects genomic drivers in NSCLC without EGFR mutations by single-plex testing: WJOG13620L.

BACKGROUND: Actionable tumor genomic alterations, primarily EGFR mutations, occur in nearly 70% of Japanese advanced nonsquamous non-small cell lung cancer (NSCLC) patients. Standard assessment of tumor tissue includes rapid testing for EGFR mutations, ALK fusions and ROS1 fusions. We conducted a prospective observational study (WJOG13620L) of follow-on next-generation sequencing of circulating tumor DNA (ctDNA) in patients without driver alterations after EGFR testing. METHODS: Patients with untreated advanced (Stage IIIB-IV or relapsed) nonsquamous NSCLC without EGFR mutations according to single-plex testing of tumor tissue, were enrolled into this study. Patients with other known driver mutations or who underwent comprehensive genomic profiling were excluded. Plasma was analyzed by Guardant360, and the primary endpoint was the proportion of patients with pathogenic gene alterations in at least one of nine genes. RESULTS: Among the 72 patients enrolled, ALK and ROS1 fusions were tested in 86.1% and 65.2%, respectively. Alterations in pre-defined genes were detected in 21 patients (29.2%; 95% confidence interval: 19.0-41.1, p < 0.001 [one-sided null hypothesis proportion of 10%]), including RET fusion (n = 1) and mutations in KRAS (n = 11), EGFR (n = 5), ERBB2 (n = 3), and BRAF (n = 1). Median time from sample submission to results was 8 days (range, 5-17 days). CONCLUSION: Rapid follow-on comprehensive testing of ctDNA should be considered prior to first-line treatment for patients with advanced nonsquamous NSCLC when no alterations are detected after single-plex tissue testing.

Mediastinal pancreatic pseudocyst diagnosed based on black pleural effusion.

Mediastinal pancreatic pseudocysts are rare complications of pancreatitis associated with alcohol consumption. Here, we report a case of mediastinal pancreatic pseudocyst. A 61-year-old Japanese woman presented to our hospital with epigastric pain and dyspnea. A chest radiograph revealed right-sided massive pleural effusion. Thoracentesis retrieved black pleural fluid with remarkably high fluid amylase levels were. Thoracic computed tomography (CT) after drainage revealed encapsulated fluid. Magnetic resonance cholangiopancreatography (MRCP) and endoscopic retrograde cholangiopancreatography (ERCP) were performed because abdominal CT and ultrasonography did not reveal any pancreatic problems. MRCP showed cystic masses and pancreatic tail cysts extending to the stomach and lower oesophagus. ERCP confirmed leakage of contrast medium from the pancreatic tail into the retroperitoneum. We diagnosed the patient with a pancreatic pseudocyst extending to the mediastinum. A mediastinal pancreatic pseudocyst should be considered a differential diagnosis in patients with black pleural fluid with a high amylase level.

A phase II study (WJOG12819L) to assess the efficacy of osimertinib in patients with EGFR mutation-positive NSCLC in whom systemic disease (T790M-negative) progressed after treatment with first- or second-generation EGFR TKIs and platinum-based chemotherapy.

BACKGROUND: Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that is an established standard treatment option for chemotherapy-naive patients with EGFR mutation-positive non-small cell lung cancer (NSCLC). However, of such patients who have received prior treatment with a first- or second-generation EGFR TKI, only approximately half are eligible for osimertinib therapy because its indication as second-line treatment and beyond is limited to metastatic NSCLC that is positive for the T790M resistance mutation of the EGFR gene. This study was initiated at the request of a dedicated network for patients with lung cancer in Japan. METHODS: We conducted a phase II study to assess the efficacy of osimertinib in patients with EGFR mutation-positive NSCLC in whom systemic disease (T790M-negative) progressed after treatment with first- or second-generation EGFR TKIs and platinum-based chemotherapy. The primary end point was response rate (assessed by a central imaging reviewer). RESULTS: From August 2020 to February 2021, 55 patients from 15 institutions were enrolled in the study. The overall response for primary analysis was achieved in 16 patients (29.1 %; 95 % CI, 17.6-42.9), which exceeded the threshold response rate necessary for analysis. Stable disease was found in 16 patients (29.1 %), and progressive disease, in 18 (32.7 %). The median length of progression-free survival (PFS) was 4.07 months (95 % CI 2.10-4.30), and the rate of 12-month PFS was 17.3 %. CONCLUSIONS: Osimertinib demonstrated modest antitumor activity against progressive EGFR T790M-negative disease.

Heterogeneous Outcomes of Immune Checkpoint Inhibitor Rechallenge in Patients With NSCLC: A Systematic Review and Meta-Analysis.

Introduction: Outcomes of immune checkpoint inhibitor (ICI) rechallenge in NSCLC remain uncertain. This study estimated the safety and efficacy of ICI rechallenge and compared rechallenge benefit among different reasons of initial ICI discontinuation in NSCLC. Methods: PubMed, EMBASE, and Cochrane Library were searched for studies on NSCLC retreated with ICI. Immune-related adverse events (irAEs), overall response rate (ORR), disease control rate (DCR), and progression-free survival (PFS) at initial ICI and rechallenge were analyzed. Results: A total of 15 studies including 442 patients between 2018 and 2022 were eligible for meta-analysis. The incidence of grade 3 or 4 irAE was lower in rechallenge than initial ICI (8.6% versus 17.8%, p < 0.001). Patients rechallenged with ICI had lower ORR and DCR than initial ICI (13.2% versus 42.4%, p < 0.001; 51.1% versus 74.0%, p < 0.001). The ORR and DCR to ICI rechallenge were both higher in patients who experienced disease progression after stopping ICI or irAE than patients with disease progression during ICI treatment (ORR: 46.2% versus 20% versus 11.4%, p = 0.003; DCR: 84.6% versus 90.0% versus 55.0%, p = 0.002). In addition, 34.7% of 69 patients with individual response to ICI and PFS experienced the same or better response to ICI rechallenge in comparison with initial ICI, although PFS in initial ICI was longer than that in ICI rechallenge (median: 8.90 versus 3.67 mo, hazard ratio = 0.44, 95% confidence interval: 0.33-0.59). Conclusions: ICI rechallenge had less severe toxicity than initial ICI treatment. Patients undergoing disease progression after ICI cessation or ICI discontinuation owing to irAE are more likely to benefit from ICI rechallenge in NSCLC.

Survival past five years with advanced, EGFR-mutated or ALK-rearranged non-small cell lung cancer-is there a "tail plateau" in the survival curve of these patients?

BACKGROUND: The prognosis of patients with NSCLC harboring oncogenic driver gene alterations, such as EGFR gene mutations or ALK fusion, has improved dramatically with the advent of corresponding molecularly targeted drugs. As patients were followed up for about five years in most clinical trials, the long-term outcomes beyond 5 years are unclear. The objectives of this study are to explore the clinical course beyond five years of chemotherapy initiation and to investigate factors that lead to long-term survival. METHODS: One hundred and seventy-seven patients with advanced, EGFR-mutated or ALK-rearranged NSCLC who received their first chemotherapy between December 2008 and September 2015 were included. Kaplan Meier curves were drawn for the total cohort and according to subgroups of patients' characteristics. RESULTS: Median OS in the total cohort was 40.6 months, the one-year survival rate was 89%, the three-year survival rate was 54%, and the five-year survival rate was 28%. Median OS was 36.9 months in EGFR-mutated patients and 55.4 months in ALK-rearranged patients. The OS curve seemed to plateau after 72 months, and most of the patients who were still alive after more than five years are on treatment. Female sex, age under 75 years, an ECOG PS of 0 to 1, ALK rearrangement, postoperative recurrence, and presence of brain metastasis were significantly associated with longer OS. CONCLUSIONS: A tail plateau was found in the survival curves of patients with advanced, EGFR-mutated and ALK-rearranged NSCLC, but most were on treatment, especially with EGFR-mutated NSCLC.

A Novel Therapeutic Strategy Targeting the Mesenchymal Phenotype of Malignant Pleural Mesothelioma by Suppressing LSD1.

Malignant pleural mesothelioma (MPM) is a highly aggressive tumor that has a low overall survival; however, no significant treatment advances have been made in the past 15 years. Large-scale molecular studies have identified a poor prognostic subset of MPM linked to the epithelial-mesenchymal transition (EMT) that may contribute toward resistance to chemotherapy, suggesting that EMT could be targeted to treat patients with MPM. Previously, we reported that histone modifiers regulating EMT could be therapeutic targets; therefore, in this study, we investigated whether targeting lysine-specific demethylase 1 (LSD1/KDM1), a histone-modifying enzyme responsible for demethylating histone H3 lysine 4 and lysine 9, could represent a novel therapeutic strategy for MPM. We suppressed LSD1 and investigated the EMT phenotype using EMT marker expression and wound-healing assay; and chemosensitivity using apoptosis assay. We found that suppressing LSD1 induces an epithelial phenotype in sarcomatoid MPM cells, while attenuating the mesenchymal phenotype sensitized MPM cells to cisplatin-induced apoptosis. Subsequent genome-wide identification, comprehensive microarray analysis, and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) to assess genome-wide changes in chromatin accessibility suggested that LSD1 directly regulates milk fat globulin protein E8 (MFGE8), an integrin ligand that is involved in the FAK pathway. Furthermore, we found that LSD1 regulates the mesenchymal phenotype and apoptosis by activating the FAK-AKT-GSK3ß pathway via a positive feedback loop involving MFGE8 and Snail expression, thereby leading to cisplatin resistance. IMPLICATIONS: This study suggests that LSD1 regulates the mesenchymal phenotype and apoptosis, and that LSD1 inhibitors could be combined with the cisplatin as a novel therapy for patients with MPM.

Zinc-finger E-box-binding homeobox 1 (ZEB1) plays a crucial role in the maintenance of lung cancer stem cells resistant to gefitinib.

BACKGROUND: Zinc-finger E-box-binding homeobox 1 (ZEB1) is an important regulator of epithelial-mesenchymal transition (EMT) and is involved in the maintenance of cancer stem cells (CSCs) via miR-200c and BMI1 pathway. Recent studies revealed that ZEB1 contributes to the EMT-mediated acquired resistance to gefitinib in EGFR-mutant non-small cell lung cancer (NSCLC). However, the precise role of ZEB1 in the maintenance of lung CSCs that lead to acquired resistance to gefitinib remains unclear. METHODS: PC9 and HCC827 NSCLC cell lines were treated with high concentrations of gefitinib, and surviving cells were referred to as "gefitinib-resistant persisters" (GRPs). ZEB1 knockdown or overexpression was performed to determine the biological significance of ZEB1 in the CSC features of GRPs, and animal models were studied for in vivo validation. Expression of ZEB1, BMI1, and ALDH1A1 was analyzed by immunohistochemistry in tumor specimens from NSCLC patients with acquired resistance to gefitinib. RESULTS: GRPs had characteristic features of mesenchymal and CSC phenotypes with high expression of ZEB1 and BMI1, and decreased miR-200c, in vitro and in vivo. ZEB1 silencing attenuated the suppression of miR-200c, resulting in the reduction in BMI1 and reversed the mesenchymal and CSC features of GRPs. Furthermore, ZEB1 overexpression induced EMT and increased the levels of CD133- and BMI1-positive GRPs in vitro and gefitinib resistance in vivo. Finally, ZEB1, BMI1, and ALDH1A1 were highly expressed in tumor specimens from EGFR-mutant NSCLC patients with gefitinib resistance. CONCLUSIONS: ZEB1 plays an important role in gefitinib-resistant lung CSCs with EMT features via regulation of miR-200c and BMI1.

A Phase II Study to Assess the Efficacy of Osimertinib in Patients With EGFR Mutation-positive NSCLC Who Developed Isolated CNS Progression (T790M-negative or Unknown) During First- or Second-generation EGFR-TKI or Systemic Disease Progression (T790M-negative) After Treatment With First- or Second-generation EGFR-TKI and Platinum-based Chemotherapy (WJOG12819L).

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that has recently been established as a standard treatment option for chemotherapy-naive patients with EGFR mutation-positive non-small-cell lung cancer (NSCLC). However, only about one-half of patients who have received prior treatment with a first- or second-generation EGFR-TKI are eligible for osimertinib therapy because its indication in the second-line setting is limited to metastatic NSCLC positive for the T790M resistance mutation of EGFR. The dose-escalation part of a study in which patients received osimertinib at doses of 20 to 240 mg once daily after the development of resistance to first- or second-generation EGFR-TKIs revealed a response rate of 21% and a median progression-free survival of 2.8 months for individuals whose tumors were negative for EGFR T790M. We have now designed a phase II study of osimertinib for patients with EGFR mutation-positive NSCLC who develop isolated central nervous system progression (T790M-negative or unknown) after first- or second-generation EGFR-TKI therapy (cohort 1) or who develop systemic disease progression (T790M-negative) after first- or second-generation EGFR-TKI therapy and platinum-based chemotherapy (cohort 2). A total of 70 patients (cohort 1, n = 17; cohort 2, n = 53) will be enrolled in this study, which originated from a suggestion of a dedicated network for patients with lung cancer in Japan.

Nintedanib inhibits epithelial-mesenchymal transition in A549 alveolar epithelial cells through regulation of the TGF-ß/Smad pathway.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disorder. Recent studies have suggested that epithelial-mesenchymal transition (EMT) of alveolar epithelial cells influences development of pulmonary fibrosis, which is mediated by transforming growth factor ß (TGF-ß). Tumor necrosis factor α (TNF-α), an important proinflammatory cytokine in IPF, has been shown to enhance TGF-ß-induced EMT. Nintedanib, a multiple tyrosine kinase inhibitor that is currently used to treat IPF, has been shown to suppress EMT in various cancer cell lines. However, the mechanism of EMT inhibition by nintedanib and its effect on TGF-ß and TNF-α signaling pathways in alveolar epithelial cells have not been fully elucidated. METHODS: A549 alveolar epithelial cells were stimulated with TGF-ß2 and TNF-α, and the effects of nintedanib on global gene expression were evaluated using microarray analysis. Furthermore, Smad2/3 phosphorylation was assessed using western blotting. RESULTS: We found that in A549 cells, TGF-ß2 and TNF-α treatment induces EMT, which was inhibited by nintedanib. Gene ontology analysis showed that nintedanib significantly attenuates the gene expression of EMT-related cellular pathways and the TGF-ß signaling pathway, but not in the TNF-α-mediated signaling pathway. Furthermore, hierarchical cluster analysis revealed that EMT-related genes were attenuated in nintedanib-treated cells. Additionally, nintedanib was found to markedly suppress phosphorylation of Smad2/3. CONCLUSION: Nintedanib inhibits EMT by mediating EMT-related gene expression and the TGF-ß/Smad pathway in A549 alveolar epithelial cells.

Activation of insulin-like growth factor-1 receptor confers acquired resistance to osimertinib in non-small cell lung cancer with EGFR T790M mutation.

BACKGROUND: Osimertinib (AZD9291) is a third-generation EGFR-tyrosine kinase inhibitor (TKI) that selectively inhibits the activating EGFR mutation and T790M mutation, and is currently used globally to treat EGFR-mutant non-small cell lung cancer (NSCLC). However, acquired resistance to osimertinib is inevitable. METHODS: We established osimertinib-resistant cells (PC9/T790M/AZDR and H1975/AZDR) derived from EGFR-mutant NSCLC cells harboring T790M mutation, and investigated the mechanism of acquired resistance to osimertinib by whole-exome sequencing and multiple phospho-receptor tyrosine kinase (RTK) array. A tumor specimen from an EGFR-mutant NSCLC patient with acquired resistance to osimertinib was also subjected to immunohistochemical analysis. RESULTS: Whole-exome sequencing analysis demonstrated that genetic alterations, such as acquisition of EGFR C797S, loss of T790M mutation, MET amplification, or mutated KRAS, MEK, BRAF, PIK3CA, were not detected. Analysis of phospho-RTK array revealed that insulin-like growth factor-1 receptor (IGF1R) was activated in PC9/T790M/AZDR and H1975/AZDR cells. Knockdown of IGF1R by siRNA as well as inhibition of IGF1R activation by linstinib (IGF1R inhibitor) significantly restored the sensitivity to osimertinib. Immunohistochemical analysis revealed that the expression level of phosphorylated IGF1R was higher in the tumor specimen from the EGFR-mutant NSCLC patient with acquired resistance to osimertinib than in the specimen collected prior to the treatment. CONCLUSIONS: IGF1R activation could occur following treatment with osimertinib in EGFR-mutant NSCLC with T790M mutation, and might be one of the mechanisms underlying osimertinib resistance. Combined treatment of osimertinib and IGF1R inhibitor might be effective in overcoming the acquired resistance to osimertinib induced by IGF1R activation. KEY POINTS: Significant findings of the study: Using osimertinib-resistant cells, we found that IGF1R activation induced by osimertinib treatment in EGFR-mutant NSCLC with T790M mutation is involved in resistance. Increased phosphorylation of IGF1R was observed in the tumor specimen from an EGFR-mutant NSCLC patient with acquired osimertinib resistance. WHAT THIS STUDY ADDS: IGF1R activation might be one of the mechanisms of osimertinib resistance. A combination therapy with osimertinib and an IGF1R inhibitor might be an optimal approach for overcoming the acquired resistance to osimertinib induced by IGF1R activation.

Role of FBXW7 in the quiescence of gefitinib-resistant lung cancer stem cells in EGFR-mutant non-small cell lung cancer.

Several recent studies suggest that cancer stem cells (CSCs) are involved in intrinsic resistance to cancer treatment. Maintenance of quiescence is crucial for establishing resistance of CSCs to cancer therapeutics. F-box/WD repeat-containing protein 7 (FBXW7) is a ubiquitin ligase that regulates quiescence by targeting the c-MYC protein for ubiquitination. We previously reported that gefitinib-resistant persisters (GRPs) in EGFR-mutant non-small cell lung cancer (NSCLC) cells highly expressed octamer-binding transcription factor 4 (Oct-4) as well as the lung CSC marker CD133, and they exhibited distinctive features of the CSC phenotype. However, the role of FBXW7 in lung CSCs and their resistance to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors in NSCLC is not fully understood. In this study, we developed GRPs from the two NSCLC cell lines PC9 and HCC827, which express an EGFR exon 19 deletion mutation, by treatment with a high concentration of gefitinib. The GRPs from both PC9 and HCC827 cells expressed high levels of CD133 and FBXW7, but low levels of c-MYC. Cell cycle analysis demonstrated that the majority of GRPs existed in the G0/G1 phase. Knockdown of the FBXW7 gene significantly reduced the cell number of CD133-positive GRPs and reversed the cell population in the G0/G1-phase. We also found that FBXW7 expression in CD133-positive cells was increased and c-MYC expression was decreased in gefitinib-resistant tumors of PC9 cells in mice and in 9 out of 14 tumor specimens from EGFR-mutant NSCLC patients with acquired resistance to gefitinib. These findings suggest that FBXW7 plays a pivotal role in the maintenance of quiescence in gefitinib-resistant lung CSCs in EGFR mutation-positive NSCLC.

Dasatinib Suppresses TGFß-Mediated Epithelial-Mesenchymal Transition in Alveolar Epithelial Cells and Inhibits Pulmonary Fibrosis.

PURPOSE: Transforming growth factor ß (TGFß)-mediated epithelial-mesenchymal transition (EMT) of alveolar epithelial cells contributes to pulmonary fibrosis. Dasatinib (DAS), a potent and broad-spectrum tyrosine kinase inhibitor, has been widely studied as an anti-cancer agent. However, the therapeutic application of DAS for pulmonary fibrosis has not been clarified. Our purpose here is to investigate the effect of DAS on TGFß1-induced EMT in human alveolar and bronchial epithelial cells in vitro and to evaluate the efficacy of DAS on lung fibrosis in vivo. METHODS: TGFß1-stimulated human alveolar epithelial (A549) and bronchial epithelial (BEAS-2B) cells were treated with or without DAS in vitro. Murine pulmonary fibrosis model was generated by injection of bleomycin (BLM). RESULTS: A549 and BEAS-2B cells exposed to TGFß1 underwent EMT, as indicated by downregulation of epithelial protein E-cadherin and induction of the mesenchymal proteins, fibronectin and type I and type IV collagen. These effects were dramatically suppressed by DAS treatment, which also prevented Smad2 and Smad3 phosphorylation. DAS inhibited TGFß1-induced cell motility and migration. Furthermore, DAS administration significantly attenuated lung fibrosis in mice by histological analysis. Treatment with DAS also significantly reduced the levels of collagen and fibronectin and phosphorylation of Smad2 in the lung tissues of the murine model. CONCLUSIONS: These findings suggest that DAS inhibited TGFß-mediated EMT of alveolar and bronchial epithelial cells and attenuated BLM-induced lung fibrosis in mice by suppressing the TGFß/Smad pathway. DAS may be a promising and novel anti-fibrotic agent for preventing lung fibrosis.

Esophageal ulcer of unknown origin complicated by left atrial myxoma.

Myxoma induces the onset of paraneoplastic syndromes by excreting various humoral mediators and is therefore known to present with diverse symptoms. A 40-year-old woman was admitted to our hospital for the treatment of an esophageal ulcer, the cause of which could not be identified on various examinations. Notably, a left atrial tumor was incidentally found on chest enhanced computed tomography. The esophageal ulcer, which was intractable to conventional therapy, improved with the administration of 5-aminosalicylate, a drug known to inhibit IL-1ß. This inhibitory action effectively suppressed the development of myxoma-induced paraneoplastic syndrome.

Areolae of the placenta in the Antarctic minke whale (Balaenoptera bonaerensis).

In this study, we examined the existence and structure of areolae and the steroidogenesis of areolar trophoblast cells in the Antarctic minke whale placenta morphologically and immunohistochemically. Placentas were collected from the 15th, 16th and 18th Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) and 1st JARPA II organized by the Institute of Cetacean Research in Tokyo, Japan. The opening and cavity of fetal areolae formed by taller columnar trophoblast cells (areolar trophoblast cells) with long microvilli and a bright cytoplasm, as compared with the trophoblast cells of the chorionic villi interdigitating with the endometrial crypts, were recognized in observations of serial sections. The opening of the areolar cavity was hidden by chorionic villi with areolar trophoblast cells. Furthermore, a closed pouch-like structure lined by tall columnar cells similar to areolar trophoblast cells within the stroma of chorionic villi was noticed and continued to the areolar cavity, with the opening seen on serial sections. In a surface investigation of the chorion and endometrium by SEM, maternal (endometrial) areolae irregularly surrounded by endometrial folds were obvious. Moreover, we distinguished areolar trophoblast cells with long microvilli attached with many blebs from trophoblast cells. In our immunohistochemical observations, a steroidogenic enzyme, cytochrome P450 side chain cleavage enzyme (P450scc), was detected with strong immunoreactivity in trophoblast cells. However, areolar trophoblast cells showed weak or no immunoreactivity for P450scc.

Structure and steroidogenesis of the placenta in the Antarctic minke whale (Balaenoptera bonaerensis).

There are few reports describing the structure and function of the whale placenta with the advance of pregnancy. In this study, therefore, the placenta and nonpregnant uterus of the Antarctic minke whale were observed morphologically and immunohistochemically. Placentas and nonpregnant uteri were collected from the 15th, 16th and 18th Japanese Whale Research Programme with Special Permit in the Antarctic (JARPA) and 1st JARPA II organized by the Institute of Cetacean Research in Tokyo, Japan. In the macro- and microscopic observations, the placenta of the Antarctic minke whale was a diffuse and epitheliochorial placenta. The chorion was interdigitated to the endometrium by primary, secondary and tertiary villi, which contained no specialized trophoblast cells such as binucleate cells, and the interdigitation became complicated with the progress of gestation. Furthermore, fetal and maternal blood vessels indented deeply into the trophoblast cells and endometrial epithelium respectively with fetal growth. The minke whale placenta showed a fold-like shape as opposed to a finger-like shape. In both nonpregnant and pregnant uteri, many uterine glands were distributed. The uterine glands in the superficial layer of the pregnant endometrium had a wide lumen and large epithelial cells as compared with those in the deep layer. On the other hand, in the nonpregnant endometrium, the uterine glands had a narrower lumen and smaller epithelial cells than in the pregnant endometrium. In immunohistochemical detection, immunoreactivity for P450scc was detected in most trophoblast cells, but not in nonpregnant uteri, suggesting that trophoblast epithelial cells synthesized and secreted the sex steroid hormones and/or their precursors to maintain the pregnancy in the Antarctic minke whale.

Immunohistochemical localization of steroidogenic enzymes in the testis of the sika deer (Cervus nippon) during developmental and seasonal changes.

Testicular steroidogenesis and spermatogenesis during developmental and seasonal changes were investigated in male sika deer (Cervus nippon), a short-day seasonal breeder, to clarify the physiological mechanisms for reproductive function. The immunohistochemical localization of steroidogenic enzymes (P450scc, P450c17, 3betaHSD and P450arom), spermatogenesis and cell proliferation were analyzed in the testes of fetal (164 to 218 days of fetal age), fawn (0 years old), yearling (1 year old) and adult (more than 2 years old) male sika deer. Three kinds of steroidogenic enzymes, P450scc, P450c17 and 3betaHSD, essential for the synthesis of testosterone were located only in the Leydig cells of the testes from the fetal period, and these localizations did not change during developmental or seasonal stages. Immunoreactivity for P450arom, a key enzyme converting testosterone to estradiol, was also localized only in the Leydig cells of testes but was also further limited to the testes of yearlings and adults. Seminiferous tubules had already formed in the fetal testes examined in the present study. Spermatogenesis started in yearlings and was more active in the breeding season. In the adult sika deer testes, the Leydig cells, which displayed immunoreactivities for steroidogenic enzymes, changed to have more cytoplasm in the breeding season than in the non-breeding season. Cell proliferation of Leydig cells was hardly observed in adult testes during seasonal changes. The present results suggested that sika deer testes start to synthesize testosterone from the fetal period, that seasonal changes in testosterone and estradiol syntheses are dependent on the quantitative variation of steroidogenic enzymes synchronized with the size of Leydig cells and that estradiol synthesized in yearling and adult testes makes a contribution to the initiation and recrudescence of spermatogenesis and spermiogenesis in the sika deer.