Akimitsu Konishi

Involvement of Histone H1.2 in Apoptosis Induced by DNA Double-Strand Breaks

It is poorly understood how apoptotic signals arising from DNA damage are transmitted to mitochondria, which release apoptogenic factors into the cytoplasm that activate downstream destruction programs. Here, we identify histone H1.2 as a cytochrome c-releasing factor that appears in the cytoplasm after exposure to X-ray irradiation. While all nuclear histone H1 forms are released into the cytoplasm in a p53-dependent manner after irradiation, only H1.2, but not other H1 forms, induced cytochrome c release from isolated mitochondria in a Bak-dependent manner. Reducing H1.2 expression enhanced cellular resistance to apoptosis induced by X-ray irradiation or etoposide, but not that induced by other stimuli including TNF-alpha and UV irradiation. H1.2-deficient mice exhibited increased cellular resistance in thymocytes and the small intestine to X-ray-induced apoptosis. These results indicate that histone H1.2 plays an important role in transmitting apoptotic signals from the nucleus to the mitochondria following DNA double-strand breaks.

EGFR Mutation Status in Japanese Lung Cancer Patients: Genotyping Analysis Using LightCycler

Purpose: Recently, somatic mutations of the epidermal growth factor receptor (EGFR) gene were found in ∼25% of Japanese lung cancer patients. These EGFR mutations are reported to be correlated with clinical response to gefitinib therapy. However, DNA sequencing using the PCR methods described to date is time-consuming and requires significant quantities of DNA; thus, this existing approach is not suitable for a routine pretherapeutic screening program. Experimental Design: We have genotyped EGFR mutation status in Japanese lung cancer patients, including 102 surgically treated lung cancer cases from Nagoya City University Hospital and 16 gefitinib-treated lung cancer cases from Kinki-chuo Chest Medical Center. The presence or absence of three common EGFR mutations were analyzed by real-time quantitative PCR with mutation-specific sensor and anchor probes. Results: In exon 21, EGFR mutations (CTG → CGG; L858R) were found from 8 of 102 patients from Nagoya and 1 of 16 from Kinki. We also detected the deletion mutations in exon 19 from 7 of 102 patients from Nagoya (all were deletion type 1a) and 4 of 16 patients from Kinki (one was type 1a and three were type 1b). In exon 18, one example of G719S mutation was found from both Nagoya and Kinki. The L858R mutation was significantly correlated with gender (women versus men, P < 0.0001), Brinkman index (600 ≤ versus 600>, P = 0.001), pathologic subtypes (adenocarcinoma versus nonadenocarcinoma, P = 0.007), and differentiation status of the lung cancers (well versus moderately or poorly, P = 0.0439), whereas the deletion mutants were not. EGFR gene status, including the type of EGFR somatic mutation, was correlated with sensitivity to gefitinib therapy. For example, some of our gefitinib-responsive patients had L858R or deletion type 1a mutations. On the other hand, one of our gefitinib-resistant patients had a G719S mutation. Conclusions: Using the LightCycler PCR assay, the EGFR L858R mutation status might correlate with gender, pathologic subtypes, and gefitinib sensitivity of lung cancers. However, further genotyping studies are needed to confirm the mechanisms of EGFR mutations for the sensitivity or resistance of gefitinib therapy for the lung cancer.

Depletion of Chk1 Leads to Premature Activation of Cdc2-cyclin B and Mitotic Catastrophe

Mitotic catastrophe occurs as a result of the uncoupling of the onset of mitosis from the completion of DNA replication, but precisely how the ensuing lethality is regulated or what signals are involved is largely unknown. We demonstrate here the essential role of the ATM/ATR-p53 pathway in mitotic catastrophe from premature mitosis. Chk1 deficiency resulted in a premature onset of mitosis because of abnormal activation of cyclin B-Cdc2 and led to the activation of caspases 3 and 9 triggered by cytoplasmic release of cytochrome c. This deficiency was associated with foci formation by the phosphorylated histone, H2AX (γH2AX), specifically at S phase. Ectopic expression of Cdc2AF, a mutant that cannot be phosphorylated at inhibitory sites, also induced premature mitosis and foci formation by γH2AX at S phase in both embryonic stem cells and HCT116 cells. Depletion of ATM and ATR protected against cell death from premature mitosis. p53-deficient cells were highly resistant to lethality from premature mitosis as well. Our results therefore suggest that ATM/ATR-p53 is required for mitotic catastrophe that eliminates cells escaping Chk1-dependent mitotic regulation. Loss of this function might be important in mammalian tumorigenesis.

Involvement of JNK in the regulation of autophagic cell death

Programmed cell death is a crucial process in the normal development and physiology of metazoans, and it can be divided into several categories that include type I death (apoptosis) and type II death (autophagic cell death). The Bcl-2 family proteins are well-characterized regulators of apoptosis, among which multidomain pro-apoptotic members (such as Bax and Bak) function as a mitochondrial gateway at which various apoptotic signals converge. Although embryonic fibroblasts from Bax/Bak double-knockout (DKO) mice are resistant to apoptosis, we have previously reported that these cells still die by autophagy in response to various death stimuli. In this study, we found that jun N-terminal kinase (JNK) was activated in etoposide- and staurosporine-treated, but not serum-starved, Bax/Bak DKO cells, and that autophagic cell death was suppressed by the addition of a JNK inhibitor and by a dominant-negative mutant of JNK. Studies with sek1−/−mkk7−/− cells revealed that disruption of JNK prevented the induction of autophagic cell death. Co-activation of JNK and autophagy induced autophagic cell death. Activation of JNK occurred downstream of the induction of autophagy, and was dependent on the autophagic process. These results indicate that JNK activation is crucial for the autophagic death of Bax/Bak DKO cells.

Cell cycle control of telomere protection and NHEJ revealed by a ts mutation in the DNA-binding domain of TRF2

TRF2 is a component of shelterin, the telomere-specific protein complex that prevents DNA damage signaling and inappropriate repair at the natural ends of mammalian chromosomes. We describe a temperature-sensitive (ts) mutation in the Myb/SANT DNA-binding domain of TRF2 that allows controlled and reversible telomere deprotection. At 32 degrees C, TRF2ts was functional and rescued the lethality of TRF2 deletion from conditional TRF2(F/-) mouse embryonic fibroblasts (MEFs). When shifted to the nonpermissive temperature (37 degrees C), TRF2ts cells showed extensive telomere damage resulting in activation of the ATM kinase and nonhomologous end-joining (NHEJ) of chromosome ends. The inactivation of TRF2ts at 37 degrees C was rapid and reversible, permitting induction of short periods (3-6 h) of telomere dysfunction in the G0, G1, and S/G2 phases of the cell cycle. The results indicate that both the induction of telomere dysfunction and the re-establishment of the protected state can take place throughout interphase. In contrast, the processing of dysfunctional telomeres by NHEJ occurred primarily in G1, being repressed in S/G2 in a cyclin-dependent kinase (CDK)-dependent manner.

Cten mRNA expression was correlated with tumor progression in lung cancers.

Cten is a recently isolated gene, which has homology with tensin suggesting that it is a focal adhesion molecule. Tensin family proteins play an important role in cell motility. We attempted to determine the influence of cten expression on clinicopathological features in patients with lung cancer who had undergone surgery. Expression of cten messenger RNA was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) in 89 lung carcinomas and adjacent histological normal lung samples using LightCycler. Cten/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA expression was not significantly different between lung cancer tissue (1.479+/-2.060) and normal lung tissue (1.528+/-1.592, P=0.8267). There was no relationship between cten/GAPDH expression and age, gender or N-status. However, tumor/normal ratio (T/N ratio) of cten/GAPDH expression was significantly higher in stage II-IV lung cancer (3.113+/-6.493) when compared with stage I lung cancer (1.237+/-1.820, P=0.0316). T/N ratio of cten/GAPDH expression was significantly higher in T4 lung cancer (4.612+/-9.726) when compared with T1 lung cancer (0.896+/-0.860, P=0.0252), and T2 lung cancer (1.636+/-2.066, P=0.0470), respectively. Thus cten/GAPDH mRNA expression has been correlated with evidence of tumor progression in terms of T and overall stage of lung cancer. Alternatively, cell motility or migration might play a role in progression of lung cancer.

Elevated serum epidermal growth factor receptor level is correlated with lymph node metastasis in lung cancer

Abstract.Background: Using an enzyme immunoassay for epidermal growth factor receptor (EGFR), we investigated whether serum EGFR levels could be used as predictors of the development and extent of lung cancer. Methods: The study included 106 lung cancer patients and 16 patients with nonmalignant thoracic disease. Serum samples were collected before clinical treatment. Results: There was no difference between serum EGFR levels in patients with lung cancer (21.275 ± 22.035 fm/ml) in comparison with those in nonmalignant-disease controls (22.630 ± 7.330 fm/ml; P = 0.8083). However, lung cancer patients with lymph node metastasis (23.515 ± 20.065 fm/ml) had significantly higher EGFR levels compared with those in patients without lymph node metastasis (16.390 ± 10.970 fm/ml; P = 0.0228). The serum EGFR levels were similar in samples from lung cancer patients with various pathological subtypes. There was no difference in the prognosis between the lung cancer group with normal EGFR levels (<850 ng/ml) and the group with elevated EGFR levels (>850 ng/ml). Conclusion: Serum EGFR levels may serve as a marker that can be used as an indicator of lymph node metastasis in lung cancer. However, there was no difference between levels in patients with lung cancer and those in nonmalignant-disease controls, indicating that the measurement of serum EGFR levels was of limited value in the detection of lung cancer.

Involvement of Beclin 1 in Engulfment of Apoptotic Cells

Background: Engulfment of apoptotic cell is facilitated by Rac1-GTPase and phosphatidylinositol 3-kinase (PI3K). Beclin 1 is known to form PI3K complex. Results: Beclin 1 was bound to Rac1, recruited to early phagocytotic cups, and required for apoptotic cell internalization. Conclusion: Beclin 1 regulates apoptotic cell engulfment in cooperation with Rac1. Significance: This report reveals a novel function of Beclin 1 in apoptotic cell clearance. Efficient apoptotic cell engulfment is important for both tissue homeostasis and immune response in mammals. In the present study, we report that Beclin 1 (a regulator of autophagy) is required for apoptotic cell engulfment. The engulfment process was largely abolished in Beclin 1 knock-out cells, and Beclin 1 knockdown significantly decreased apoptotic cell internalization in macrophage and fibroblast cell lines. Beclin 1 was recruited to the early phagocytic cup along with the generation of phosphatidylinositol 3-phosphate and Rac1, which regulates actin dynamics in lamellipodia. No lamellipodia were formed in Beclin 1 knock-out cells, and Beclin 1 knockdown completely inhibited the promotion of engulfment by ectopic expression of Rac1. Beclin 1 was co-immunoprecipitated with Rac1. These data indicate that Beclin 1 coordinates actin dynamics and membrane phospholipid synthesis to promote efficient apoptotic cell engulfment.

Elevated Serum Epidermal Growth Factor Receptor Level in Stage IV Thymoma

Using the enzyme immunoassay for epidermal growth factor receptor (EGFR), we investigated whether serum EGFR levels could be used as a predictor of the development and extension of thymoma. Serum samples were collected from 31 patients with thymoma and 16 patients with nonmalignant thoracic disease before clinical treatment. There was no difference between the serum EGFR levels of the patients with thymoma and the nonmalignant controls, being 49.1 ± 136.3 and 22.6 ± 7.3 fm/ml, respectively (P = 0.11). However, patients with stage IV thymoma had significantly higher EGFR levels than those with stage I or stage II thymoma, the respective values being 127.8 ± 243.9, 10.9 ± 9.2 (P = 0.02), and 19.7 ± 10.6 (P = 0.0433) fm/ml. The serum EGFR levels were similar in the pathological subtypes. These findings suggest that serum EGFR levels may serve as a marker that could be used as a diagnostic indicator of the invasion of thymoma.

Endostatin gene transfection using a cationic lipid: advantages of transfection before tumor cell inoculation and repeated transfection.

Intravenous endostatin gene transfection results in tumor suppression in a murine pulmonary metastasis model. We transfected the endostatin gene at different times, in order to achieve an optimal protective effect. pST2-Endo encoding murine endostatin was injected in a complex with cationic lipid. Pulmonary metastases were caused by intravenous injection of murine fibrosarcoma cells. Mice were observed for 14 days following fibrosarcoma cell inoculation (FSI). In the study groups, the animals were transfected with pST2-Endo at three different times: 2 days before and 3 and 7 days after FSI. In the group transfected with pST2-Endo 2 days before FSI, the weights of the lungs and tumor-occupied area ratio were significantly less than in the other groups. Significant inhibition of tumor neovascularization was documented by means of CD31 immunohistochemistry. The effect of repeated endostatin transfection on survival after FSI was determined. Animals repeatedly transfected with the endostatin gene survived significantly longer than the groups treated with a single endostatin gene transfection. A stable endostatin-expressing fibrosarcoma transfectant was created and tested for migration and invasion. Compared with controls, endostatin expression reduced migration and invasion by 15%. It is concluded that endostation gene transfection before FSI and repeated transfection thereafter results in significant tumor suppression.