To investigate the regulatory mechanisms of the cell cycle transition from M phase to M phase in meiotic cycles, a Xenopus oocyte extract that performs the M–M transition has been developed. Using ...the meiotic extract, we found that a low level of Cdc2 activity remained at the exit of meiosis I (MI), due to incomplete degradation of cyclin B. The inactivation of the residual Cdc2 activity induced both entry into S phase and tyrosine phosphorylation on Cdc2 after MI. Quantitative analysis demonstrated that a considerable amount of Wee1 was present at the MI exit and Cdc2 inhibitory phosphorylation during this period was suppressed by the dominance of Cdc2 over Wee1. Consistently, the addition of more than a critical amount of Wee1 to the extract induced Cdc2 inhibitory phosphorylation, changing the M–M transition into an M–S–M transition. Thus, the Cdc2 activity remaining at MI exit is required for suppressing entry into S phase during the meiotic M–M transition period.
In meiotic cell cycles, meiosis I (MI) is followed by meiosis II (MII) without an intervening S phase, whereas in mitotic cell cycles, an S phase necessarily alternates with an M phase. For the study ...of mitotic cell cycles, extracts prepared from unfertilized and parthenogenetically activated Xenopus eggs have been very useful as they can perform the progression of mitotic cycles in vitro. To establish a cell-free system to study the regulatory mechanisms of meiotic transition from MI to MII, extracts have been prepared from maturing Xenopus oocytes isolated from ovaries, stimulated with progesterone to induce the resumption of meiosis, and arrested at meiotic metaphase I by cold treatment. In oocyte extracts, the activity of cyclin B-Cdc2 complexes, the M phase inducer, fluctuates in the same manner as it does in maturing oocytes during the MI to MII transition period. By the use of oocyte extracts, it has been found that incomplete inactivation of Cdc2 at the end of MI is required for meiotic M-M transition. The meiotic extract should provide a useful tool to elucidate molecular mechanisms of meiotic M to M transition, including a role of Mos/mitogen-activated protein kinase cascade in the suppression of S phase entry after MI exit. In this chapter, we describe methods for the preparation and the uses of meiotic extracts. As a comparison, we also include a protocol for the preparation of mitotic extracts.
Chromobox 2 (CBX2), an epigenetic reader and component of Polycomb Repressor Complex 1 (PRC1), is highly expressed in >75% of high-grade serous carcinoma (HGSC). Increased CBX2 expression is ...associated with poorer survival, while CBX2 knockdown leads to improved chemotherapy sensitivity. In an HGSC immune competent murine model, knockdown of CBX2 decreased tumor progression. We sought to explore the impact of modulation of CBX2 on the tumor immune microenvironment (TIME), understanding that the TIME plays a critical role in disease progression and development of therapy resistance. Exploration of existing datasets demonstrated that elevated CBX2 expression significantly correlated with the specific immune cell types in the TIME. RNA-seq and pathway analysis of differentially expressed genes demonstrated immune signature enrichment. Confocal microscopy and co-culture experiments found modulation of CBX2 leads to increased recruitment and infiltration of macrophages. Flow cytometry of macrophages cultured with CBX2 overexpressing cells showed increased M2-like macrophages and decreased phagocytosis activity. Cbx2 knockdown in the Trp53, Brca2 null ID8 syngeneic murine model (ID8 Trp53-/- Brca2-/-) led to decreased tumor progression compared to control. NanoString Immuno-Oncology Panel analysis suggested knock down in Cbx2 shifts immune cell composition, with an increase in macrophages. Multispectral immunohistochemistry further confirmed an increase in macrophage infiltration. Increased CBX2 expression leads to recruitment and polarization of pro-tumor macrophages and targeting CBX2 may serve to modulate the TIME to enhance the efficacy of immune therapies.Chromobox 2 (CBX2), an epigenetic reader and component of Polycomb Repressor Complex 1 (PRC1), is highly expressed in >75% of high-grade serous carcinoma (HGSC). Increased CBX2 expression is associated with poorer survival, while CBX2 knockdown leads to improved chemotherapy sensitivity. In an HGSC immune competent murine model, knockdown of CBX2 decreased tumor progression. We sought to explore the impact of modulation of CBX2 on the tumor immune microenvironment (TIME), understanding that the TIME plays a critical role in disease progression and development of therapy resistance. Exploration of existing datasets demonstrated that elevated CBX2 expression significantly correlated with the specific immune cell types in the TIME. RNA-seq and pathway analysis of differentially expressed genes demonstrated immune signature enrichment. Confocal microscopy and co-culture experiments found modulation of CBX2 leads to increased recruitment and infiltration of macrophages. Flow cytometry of macrophages cultured with CBX2 overexpressing cells showed increased M2-like macrophages and decreased phagocytosis activity. Cbx2 knockdown in the Trp53, Brca2 null ID8 syngeneic murine model (ID8 Trp53-/- Brca2-/-) led to decreased tumor progression compared to control. NanoString Immuno-Oncology Panel analysis suggested knock down in Cbx2 shifts immune cell composition, with an increase in macrophages. Multispectral immunohistochemistry further confirmed an increase in macrophage infiltration. Increased CBX2 expression leads to recruitment and polarization of pro-tumor macrophages and targeting CBX2 may serve to modulate the TIME to enhance the efficacy of immune therapies.
In the early embryonic cell cycle, exit from M phase is immediately followed by entry into S phase without an intervening gap phase. To understand the regulatory mechanisms for the cell cycle ...transition from M to S phase, we examined dependence on Cdc2 inactivation of cell-cycle events occurring during the M-S transition period, using Xenopus egg extracts in which the extent of Cdc2 inactivation at M phase exit was quantitatively controlled. The result demonstrated that MCM binding to and the initiation of DNA replication of nuclear chromatin occurred depending on the decrease of Cdc2 activity to critical levels. Similarly, we found that Cdc2 inhibitory phosphorylation and cyclin B degradation were turned on and off, respectively, depending on the decrease in Cdc2 activity. However, their sensitivity to Cdc2 activity was different, with the turning-on of Cdc2 inhibitory phosphorylation occurring at higher Cdc2 activity levels than the turning-off of cyclin B degradation. This means that, when cyclin B degradation ceases at M phase exit, Cdc2 inhibitory phosphorylation is necessarily activated. In the presence of constitutive synthesis of cyclin B, this condition favors the occurrence of the Cdc2 inactivation period after M phase exit, thereby ensuring progression through S phase. Thus, M phase exit and S phase entry are coordinately regulated by the Cdc2 activity level in the early embryonic cell cycle.
IntroductionOsimertinib may be effective in treating central nervous system (CNS) metastasis, but its efficacy in treating radiation therapy (RT)-naive metastasis is unclear. The OCEAN study assessed ...the efficacy of osimertinib against RT-naive CNS metastasis in patients previously treated (T790M cohort) and untreated patients (first-line cohort) with EGFR mutation. Here, we report the results of the first-line cohort.MethodsPreviously untreated patients with RT-naive CNS metastasis and EGFR mutation-positive NSCLC were treated with osimertinib. The brain metastasis response rate (BMRR), progression-free survival (PFS), and overall survival in the first-line cohort were secondary end points.ResultsA total of 26 patients were enrolled in the study between September 2019 and July 2020. The median age was 72.0 years with 80.8% female. There were 20 patients who had multiple CNS metastases. BMRR assessed by PAREXEL criteria was 76.9% (90% confidence interval CI: 63.3%-90.5%), BMRR assessed by Response Evaluation Criteria in Solid Tumors was 76.9% (95% CI: 54.0%-99.8%), and median PFS of CNS metastasis was 22.0 months (95% CI: 9.7 mo-not reached). The overall response rate was 64.0% (95% CI: 45.2%-82.8%), median PFS was 11.5 months (95% CI: 6.9 mo-not reached), and median survival time was 23.7 months (95% CI: 16.5 mo-not reached). Paronychia and increased creatinine level were the most frequent nonhematological toxicities observed in 13 patients (50%). Grade three and higher adverse events were less than 10%, and there were no treatment-related deaths. Pneumonitis was observed in five patients (19.2%).ConclusionsThese results suggest that osimertinib is effective in untreated patients with RT-naive asymptomatic CNS metastasis in a clinical practice first-line setting.Trial registrationUMIN identifier: UMIN000024218. jRCT identifier: jRCTs071180017.
Objective: We previously reported that macrophages contribute to the pathogenesis of refractory nephrotic syndrome (NS). To elucidate the mechanism behind macrophage accumulation and to identify a ...predictive biomarker of steroid responsiveness, we compared differences in cytokine and chemokine levels in serum and urine between steroid-sensitive (SSNS) and steroid-resistant (SRNS) children with NS.Methods: Eighteen children with NS (7.1±4.3 years; male-to-female ratio, 12:6) were divided into an SSNS group (n=10) and an SRNS group (n=8) according to their clinical course. Serum and urinary samples were collected at the time of onset and remission. Samples from age-matched healthy children were used as controls (n=15). Cytokines and chemokines were measured using a cytometric bead array kit.Results: Clinical findings and laboratory data at sampling were comparable between the SRNS and SSNS groups. Serum cytokines and chemokines did not significantly differ at the time of onset between remission and control groups. In contrast, at onset, several urinary chemokines were significantly elevated in children with NS (IP-10, MCP-1, MIG, RANTES; all p<0.01). Urinary MCP-1 levels were significantly elevated in the SRNS group compared with the SSNS group (p<0.01).Conclusions: Chemokines might be associated with the pathogenesis of NS. Increased urinary excretion of MCP-1 in children with SRNS is a potential predictive biomarker of steroid responsiveness in idiopathic NS. Further histological studies, including macrophage accumulation, are required to determine the mechanisms of steroid resistance in refractory NS.
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