RNA interference (RNAi) is a posttranscriptional gene-silencing event in which short double-stranded RNA (siRNA) degrades target mRNA. Because of its potent and highly specific gene-silencing effect, RNAi is expected to be used in the treatment of various diseases. Cancer is one of the major targets of RNAi-based therapy, because silencing oncogenes or other genes contributing to tumor progression can be target genes for RNAi. The delivery of RNAi effector to target cells is one of the key factors determining therapeutic efficacy, because gene silencing is limited to cells reached by RNAi effectors. Tumor cell lines stably expressing reporter genes were confirmed to be effective in sensitively and quantitatively evaluating RNAi effects in tumor cells in vitro and in vivo. Quantitative analyses of the gene-silencing effect revealed that short-hairpin RNA expressing plasmid DNA (pshRNA) has more durable effects than siRNA. Intratumoral injection of RNAi effectors was effective in suppressing target gene expression in tumor cells, and silencing of beta-catenin or hypoxia-inducible factor-1alpha (HIF-1alpha) significantly inhibited tumor growth. RNAi effectors were successfully delivered to tumor cells colonizing the liver through the vascular route. We found that tumor-bearing liver showed elevated HIF-1alpha expression in the cells, and the silencing of the expression in normal liver cells is also effective in inhibiting metastatic tumor growth. These results indicate the possibility of RNAi-based cancer therapy.

Gene rearrangement is an important diagnostic marker of malignant lymphoma, and rearrangements of the immunoglobulin heavy chain (IgH) and T-cell receptor gamma chain (TCRgamma) genes are useful markers for Band T-cell lymphoma, respectively. A polymerase chain reaction (PCR) can be used to analyze clonality in formalin-fixed paraffin-embedded specimens. We performed 73 monoclonal analyses of such specimens of lymphoma tissues and examined the ability to diagnose malignant lymphoma by this method. Monoclonality of lymphoma cells was found in 71.9% and 78.9% of specimens with IgH and TCRgamma gene rearrangements, respectively. Therefore, in diagnosing cases of non-Hodgkin lymphoma in which neoplasms and reactive lymphoid tissues are difficult to identify by morphological and immunohistochemical findings, PCR-based monoclonal analysis may allow confirmation of a pathological diagnosis of malignant lymphoma.

We report a case of acute leukemia with an isolated isochromosome 17q karyotypic abnormality, which may be transformed from myeloproliferative disease (MPD)/myelodysplastic syndrome (MDS). A 69-year-old male patient with 27% of blasts in the peripheral blood underwent hematological examinations including cytochemical staining of cells such as myeloperoxydase (MPO), surface marker study on blasts, chromosomal test and bcr-abl mRNA analysis. The cytological and molecular findings (MPO-positive, myeloid marker CD13 expression (67.3%) and megakaryocytic marker CD41 expression (24.8%)) indicated that the blasts were consistent with myeloid leukemic cells partially committed to megakaryocytes. He was diagnosed as having leukemic transformation from MPD/MDS based on history of leukocytosis and thrombocytosis, isolated i(17q), bcr-abl negative, hepatosplenomegaly, increased eosinophil/basophil count and cytologic dysplasia. Positivity of BMI-1 in CD34+ blasts was 25.8% at the diagnosis and anti-leukemic drugs including anthracyclines were effective for his disease control during 6 months. However, the CD34+ cells turned out to highly express BMI-1 (83.1%), and leukemic cells started to increase progressively following which the leukemic cells failed to respond efficiently to any anti-leukemic drugs. Thus, expression of BMI-1 was well correlated with the disease progression, growth ability of blasts and resistance to anti-cancer drugs, indicating that BMI-1 positivity in CD34+blasts is an excellent molecular marker for disease progression and prognosis in such patients.

A 47-year-old woman was admitted to our hospital in December 1994 with polycythemia. The patient's red blood cell volume was 33 ml/kg and bone marrow cytology was able to rule out other myeloproliferative diseases such as chronic myelogenous leukemia, essential thrombocytosis and myelofibrosis. The patient was diagnosed as having polycythemia vera. She had undergone only phlebotomy until 1999 when the thrombocytosis appeared, subsequent to which she was treated with oral hydroxyurea. However, in March 2006, she developed upper abdominal pain and was admitted to our hospital on March 14th, 2006. Computed tomography scan revealed thromboses in the portal and superior mesenteric veins. Anticoagulation therapy delivered intravenously via the superior mesenteric vein dramatically improved her symptoms and liver function. She is currently on anticoagulation therapy in our outpatient clinic.

Imatinib mesilate, which efficiently inhibits BCR-ABL,and KIT as well as platelet-derived growth factor receptor (PDGF-R) kinases, is highly effective for clinical treatment of CML, Ph+ALL, and advanced GIST with good tolerability, respectively. Acquired resistance to the drug,however, becomes an clinically emerging problem with long-standing use. Meanwhile, sunitinib malate,which inhibits three VEGF-Rs and FLT 3 in addition to KIT as well as PDGF-R, was clinically evaluated in the phase II clinical trials for imatinib-resistant or intolerant GIST, and advanced renal cell carcinoma in Japan. Sunitinib is therapeutically effective for both on imatinib-resistant GIST and advanced renal cell carcinoma with modest tolerability, and is now under review for approval in Japan.

Epidermal growth factor receptor (EGFR) gene mutations are frequent in lung cancer of Asian ethnicity, female gender, non-smokers,and of adenocarcinoma histology. About 80% of the patients with EGFR mutations respond to EGFR tyrosine kinase inhibitor (TKI) including gefitinib and erlotinib, while only 10% of those without EGFR mutations do so. Therefore, EGFR mutation is being recognized as one of the most reliable predictive factors in gefitinib treatment. Another important issue in clinical practice is fatal interstitial lung disease (ILD) in patients with gefitinib treatment, especially for Asian patients. A nested case-control study recently conducted in Japan identified some risk factors which cause ILD. About half of the acquired resistance to gefitinib that almost always occurs during the course of gefitinib administration is reportedly caused by secondary mutation at codon 79 0 (T 79 0 M). EGFR-TKIs are not universally effective for lung cancer,but these drugs are effective in patients who have particular characteristics. Therefore, patients who would benefit from gefitinib therapy should be included in clinical trials. Based on this concept, phaseIII clinical trials comparing gefitinib monotherapy with standard platinum-based chemotherapy in lung cancer patients with EGFR mutations are ongoing.