Novel MEK inhibitor trametinib and other retinoblastoma gene (RB)-reactivating agents enhance efficacy of 5-fluorouracil on human colon cancer cells.

Chemotherapy for colorectal cancer has become more complicated and diversified with the appearance of molecular-targeting agents. 5-Fluorouracil (5-FU) has been a mainstay of chemotherapy for colorectal cancer, but it is still unknown whether the combining of 5-FU with novel molecular-targeting agents is effective. Thymidylate synthase (TS) is a direct target of 5-FU, and the low TS level has been generally supposed to sensitize 5-FU's efficacy. We therefore hypothesized that RB-reactivating agents could enhance the efficacy of 5-FU, because the RB-reactivating agents could suppress the function of transcription factor E2F of TS gene promoter. We used three RB-reactivating agents, trametinib/GSK1120212 (MEK inhibitor), fenofibrate (PPARα agonist), and LY294002 (PI3K inhibitor), with 5-FU against human colon cancer HT-29 and HCT15 cells. Trametinib induced p15 and p27 expression and reduced cyclin D1 levels in HT-29 cells. Fenofibrate also dephosphorlated ERK1/2 and reduced cyclin D1 levels in HT-29 cells. LY294002 induced p27 expression in HCT15 cells. All three agents caused dephosphorylation of RB protein and G1-phase arrest with a reduction of TS expression. As a consequence, the combination of 5-FU with each of the agents resulted in a significant decrease of colony numbers in HT-29 or HCT15 cells. These results suggest "RB-reactivation therapy" using molecular-targeting agents to be a new strategy for 5-FU-based chemotherapy. In particular, we strongly expect trametinib, which was discovered in Japan and was recently submitted to FDA for approval, to be used together with established regimens for colorectal cancer.

Simultaneous detection of JAK2, CALR, and MPL mutations and quantitation of JAK2 V617F allele burden in myeloproliferative neoplasms using the quenching probe-Tm method in i-densy IS-5320.

INTRODUCTION: Accurate detection of myeloproliferative neoplasms (MPN)-associated gene mutations is necessary to correctly diagnose MPN. However, conventional gene testing has various limitations, including the requirement of skilled technicians, cumbersome experimental procedures, and turnaround time of several days. The gene analyzer i-densy IS-5320 allows gene testing using the quenching probe-Tm method. Specifically, pretreatment of samples including DNA extraction, amplification and detection of genes, and analysis of results are performed in a fully automatic manner after samples and test reagents are added into this system, which is compact and can be easily installed in a laboratory. The aim of this study is to investigate the sensitivity and specificity associated with the simultaneous detection of MPN-associated gene mutations. METHODS: We conducted an analysis of MPN-associated genes using i-densy IS-5320. We analyzed 384 samples (171 JAK2 V617F mutations, 10 JAK2 exon12 mutations, 104 CALR mutations, and 26 MPL mutations) that had been examined using conventional approaches such as allele-specific polymerase chain reaction (PCR), droplet digital PCR, and the direct sequencing method. RESULTS: The detection accuracy of JAK2 V617F, JAK2 exon 12, CALR, and MPL was 100.0% (383/383), 99.7% (383/384), 100.0% (370/370), and 99.7% (377/378), respectively. There was a strong positive correlation between the JAK2 V617F allele burden measured using conventional methods and i-densy IS-5320 (r = .989). CONCLUSION: Overall, i-densy IS-5320 exhibited good accuracy in terms of analyzing MPN-associated genes; thus, it can serve as a replacement for conventional methods of MPN-associated gene testing.

Cyclin-dependent kinase inhibitor SU9516 enhances sensitivity to methotrexate in human T-cell leukemia Jurkat cells.

Methotrexate (MTX) has been used to treat various hematological malignancies. Since MTX prevents tumor cells from proliferating by inhibiting dihydrofolate reductase (DHFR), DHFR expression is a key determinant of resistance to MTX in malignant hematological tumor cells. The antiproliferative effect of MTX was significantly enhanced by the knockdown of DHFR expression by siRNA in Jurkat cells. Therefore, a novel strategy down-regulating DHFR expression seems promising for enhancing sensitivity to MTX. We found that SU9516, a cyclin-dependent kinase inhibitor, reduced the expression of both DHFR mRNA and protein. Moreover, we found that DHFR promoter activity was attenuated by SU9516 dependent on the E2F site. Finally, pretreatment with SU9516 significantly enhanced sensitivity to MTX in a colony formation assay. We conclude that a combination of cyclin-dependent kinase inhibitors and MTX may be useful for overcoming resistance to MTX.