Janus kinase 2 (JAK2) is an essential non-receptor type tyrosine kinase for various cytokine signals. In 2005, a somatic JAK2 mutation (V617F) was found in the majority of myeloproliferative neoplasm (MPN) patients. It has been shown that the V617F mutation caused the constitutive activation of JAK2, exhibiting the cytokine-independent survival and proliferation of Ba/F3 cells. In addition, tumorigenesis was induced after a transplantation of Ba/F3 cells expressing JAK2 V617F mutant in nude mice, suggesting that JAK2 V617F mutant behaves as a potent oncogene product. We found that JAK2 V617F mutant causes aberrant activation of a transcription factor c-Myc, which is critical for the JAK2 V617F mutant-caused oncogenic activities. In the screening of genes which expression was induced by JAK2 V617F mutant, we detected the significant induction of target genes of c-Myc such as Aurora kinase A (Aurka) and ornithine decarboxylase (ODC). Interestingly, JAK2 V617F mutant enhanced resistance to cisplatin (CDDP)-induced DNA damage and ectopic expression of Aurka in Ba/F3 cells exhibited similar resistance to CDDP. Conversely, knockdown and inhibition of Aurka in cells expressing JAK2 V617F mutant abolished the resistance to CDDP, suggesting that Aurka is most likely critical for resistance to DNA damage in cells transformed by JAK2 V617F mutant. In addition, we found that ODC inhibitor, DL-α-difluoromethylornithine (DFMO) prevented the proliferation of the JAK2 V617F mutant-induced transformed cells. Taking these observations together, c-Myc plays an essential role in JAK2 V617F mutant-induced hematopoietic disorder and would be a good target for the treatment of MPN.

The products of proto-oncogene play critical roles in the development or maintenance of multicellular societies in animals via strict regulatory systems. When these regulatory systems are disrupted, proto-oncogenes can become oncogenes, and thereby induce cell transformation and carcinogenesis. To understand the molecular basis for development of the regulatory system of proto-oncogenes during evolution, we screened for ancestral proto-oncogenes from the unicellular choanoflagellate Monosiga ovata (M. ovata) by monitoring their transforming ability in mammalian cells; consequently, we isolated a Pak gene ortholog, which encodes a serine/threonine kinase as a 'primitive oncogene'. We also cloned Pak orthologs from fungi and the multicellular sponge Ephydatia fluviatilis, and compared their regulatory features with that of M. ovata Pak (MoPak). MoPak is constitutively active and induces cell transformation in mammalian cells. In contrast, Pak orthologs from multicellular animals are strictly regulated. Analyses of Pak mutants revealed that structural alterations in the auto-inhibitory domain (AID) are responsible for the enhanced kinase activity and the oncogenic activity of MoPak. Furthermore, we show that Rho family GTPases-mediated regulatory system of Pak kinase is conserved throughout the evolution from unicellular to multicellular animals, but the MoPak is more sensitive to the Rho family GTPases-mediated activation than multicellular Pak. These results show that maturation of AID function was required for the development of the strict regulatory system of the Pak proto-oncogene, and support the potential link between the development of the regulatory system of proto-oncogenes and the evolution of multicellularity. Further analysis of oncogenic functions of proto-oncogene orthologs in the unicellular genes would provide some insights into the mechanisms of the destruction of multicellular society in cancer.

Recent developments in diagnostic radiology, which have enabled accurate differential diagnoses of brain tumors, have been well described in the last three decades. MR and PET imaging can also provide information to predict histological grades and prognoses that might influence treatment strategies. However, high-grade astrocytomas consist of many different subtypes that are associated with different imaging and histological characteristics. Hemorrhage and necrosis results in a variety of imaging features, and infiltrative tumor growth entrapping normal neurons may cause different clinical manifestations. We reviewed patients with high-grade astrocytomas that showed various imaging characteristics, with special emphasis on initial symptoms and histological features. Clinicopathological characteristics of astrocytomas were also compared with other malignant tumors. Neurological deficits were not notable in patients with grade 3-4 astrocytomas when they showed infiltrative tumor growth, while brain metastases with compact cellular proliferation caused more neurological symptoms. Infiltrative tumors did not show any enhancing masses on MR imaging, but these tumors may show intratumor heterogeneity. Seizures were reported to be more frequent in low-grade glioma and in secondary glioblastoma. Tumor heterogeneity was also reported in molecular genetic profile, and investigators identified some subsets of astrocytomas. They investigated IHD1/2 mutation, EGFR amplification, TP53 mutation, Ki-67 index, etc. In summary, high-grade astrocytomas are not homogenous groups of tumors, and this is associated with the heterogeneity of clinical manifestation, image characteristics, and histopathological findings. Molecular studies may explain the tumor heterogeneity in the near future.

We report a 69-year-old male with CD3-positive peripheral T-cell lymphoma, not otherwise specified (PTCL-nos). Interestingly, tumor cells slightly expressed CD20 as well. Southern analyses of the tumor cells showed rearrangement for only the T cell receptor gene but not the immunoglobulin genes. This patient achieved partial remission with a treatment regimen of THP-COP excluding prednisolone, but died of pneumonia. Although CD20-positive PTCL is rare, a review of the reported cases suggests that CD20-positive PTCL has a poor prognosis and that bone marrow infiltration of tumor cells results in a poorer prognosis in CD20-positive PTCL than in usual PTCL. By accumulating cases of this rare entity of lymphoma, we need to clarify the biological nature of the tumor cells and usefulness of rituximab combined with standard chemotherapy.

We conducted a retrospective study to evaluate outcomes and prognostic factors of newly diagnosed patients with t(8;21) acute myeloid leukemia (AML). There were 70 patients (43 men and 27 women) with a median age of 48 years old (range, 17∼76 years old). Sixty-five patients achieved complete remission (CR) after induction chemotherapy. Fifty-seven patients received consolidation chemotherapy based on the policy of not performing allogeneic hematopoietic stem cell transplantation (allo-HSCT) at the time of first CR. Twenty-seven of the 57 patients relapsed (relapse rate, 47%). The median time from the achievement of the first CR to relapse was 307 days (96∼1,256 days). A white blood cell count of more than 25,400/μl at diagnosis was associated with a higher relapse rate than a white blood cell count of less than or equal to 25,400/μl (75% vs. 43%, P=0.04). Nineteen of the 25 relapsed patients who received re-induction therapy experienced a second CR (second CR rate, 76%). Twenty-six patients (5 with first CR, 12 with second CR, and 9 without remission) received allo-HSCT. The five-year overall survival and disease-free survival rates were 61% and 45%, respectively. Patients with t(8;21) AML had a high CR rate, but about half of them relapsed. However, this report could not show prognostic factors for the identification of patients who should receive allo-HSCT at the time of their first CR.

Epigenetic alterations such as DNA methylation play a key role in silencing genes in carcinogenesis. DNA methylation leads to the silencing of a variety of genes involved in cell-cycle control, apoptosis, cell signaling and DNA repair in gastrointestinal cancer. The recent development of methylation analysis offers a quantitative, high sensitivity, high throughput and reliable method. This approach enabled us to apply methylation analysis in a clinical setting. The miR-34b/c gene is a tumor suppressor that is frequently silenced by DNA methylation in colorectal and gastric cancer (GC). Accurate preoperative diagnosis of invasiveness is essential for selecting appropriate therapeutic options for colorectal cancer, but the distinction between invasive and non-invasive colorectal tumor is often difficult. Methylation levels of miR-34b/c in colorectal washing fluid were highly discriminative between invasive and non-invasive tumors. Previous reports show that H. pylori infection, which plays an important role in gastric carcinogenesis, induces the methylation of various genes in the noncancerous gastric mucosae. These finding suggest that the accumulation of aberrant DNA methylation in noncancerous gastric mucosa is involved in the epigenetic field defect. Methylation of miR-34b/c was significantly elevated in noncancerous gastric mucosae of multiple GC patients compared with those of single GC patients and H. pylori-positive healthy individuals. These results suggest that methylation might be a useful marker for the diagnosis and risk assessment of cancer.