Summary ERK signaling requires RAS-induced RAF dimerization and is limited by feedback. Activated BRAF mutants evade feedback inhibition of RAS by either of two mechanisms. BRAF V600 mutants are activated monomers when RAS activity is low; all other activating BRAF mutants function as constitutive RAS-independent dimers. RAF inhibitors effectively inhibit mutant monomers, but not dimers; their binding to one site in the dimer significantly reduces their affinity for the second. Tumors with non-V600E BRAF mutants are insensitive to these drugs and increased expression of BRAF V600E dimers causes acquired resistance. A compound that equally inhibits both sites of mutant RAF dimers inhibits tumors driven by either class of mutants or those BRAF V600E tumors with dimer-dependent acquired resistance to monomer-specific inhibitors.

Purpose IFITM3, an interferon-inducible gene, is overexpressed in human colorectal cancer. In this study, we sought to determine the clinical significance and underlying mechanisms of its dysregulated expression in human colon tumor specimens and murine models of this disease. Experimental Design IFITM3 expression in a tissue microarray of tumor and matched normal colon tissue specimens and lymph node metastasis specimens obtained from 203 patients with colon cancer was measured immunohistochemically. Results IFITM3 was expressed at higher levels in colon tumors and, particularly, nodal metastases than in normal colon tissue. A Cox proportional hazards model showed that IFITM3 expression was an independent prognostic factor for disease-free survival in patients with colon cancer. Knockdown of IFITM3 expression by a specific small interfering RNA significantly suppressed the proliferation, colony formation, migration, and invasion of colon cancer cells in vitro and tumor growth and metastasis in a xenograft model. Restored expression of KLF4, a putative tumor suppressor, downregulated IFITM3 expression in colon cancer cells in vitro. Two KLF4-binding sites in the IFITM3 promoter bound specifically to KLF4 protein in a chromatin immunoprecipitation assay and promoter mutagenesis analyses. Specific deletion of KLF4 led to IFITM3 overexpression in colon mucosa in Villin-Cre+;Klf4fl/fl mice. An inverse correlation between loss of KLF4 expression and IFITM3 overexpression was evident in human colon tumors. Conclusion these clinical and mechanistic findings indicate that IFITM3 is a direct transcriptional target of KLF4 and that dysregulated KLF4 expression leads to aberrant IFITM3 expression, thus contributing to colon cancer progression and metastasis.

Translational relevanceHepatocyte growth factor (HGF) is involved in at least three important steps of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) resistance in EGFR mutant lung cancer, inducing resistance to reversible EGFR-TKIs by restoring Met/Gab1/PI3K/Akt pathways, inducing resistance to next-generation EGFR-TKIs (irreversible TKI and mutant-selective EGFR-TKI), and accelerating the emergence of EGFR-TKI-resistant clones by continuous exposure to HGF. Therefore, HGF may be an ideal target for overcoming EGFR-TKI resistance in EGFR mutant lung cancer.

a b s t r a c tMicroRNAs (miRNAs) act as key regulators of multiple cancers. miR-329 functions as a tumor suppressor in some malignancies. However, its role in neuroblastoma remains poorly understood. We found that miR-329 was decreased in metastatic tumor tissues compared with matched primary tumor tissues. Forced overexpression of miR-329 substantially suppressed cell proliferation, colony formation, migration, and invasion of neuroblastoma cells. Lysine-specific demethylase 1 (KDM1A) was found to be a target of miR-329. Furthermore, down-regulation of KDM1A by shRNA performed similar effects with overexpression of miR-329. Overexpression of KDM1A partially reversed the tumor suppressive effects of miR-329 in neuroblastoma cells. Collectively, miR-329 may suppress neuroblastoma cell growth and motility partially by targeting KDM1A.

One of many types of extracellular vesicles (EVs), exosomes are nanovesicle structures that are released by almost all living cells that can perform a wide range of critical biological functions. Exosomes play important roles in both normal and pathological conditions by regulating cell-cell communication in cancer, angiogenesis, cellular differentiation, osteogenesis, and inflammation. Exosomes are stable in vivo and they can regulate biological processes by transferring lipids, proteins, nucleic acids, and even entire signaling pathways through the circulation to cells at distal sites. Recent advances in the identification, production, and purification of exosomes have created opportunities to exploit these structures as novel drug delivery systems, modulators of cell signaling, mediators of antigen presentation, as well as biological targeting agents and diagnostic tools in cancer therapy. This review will examine the functions of immunocyte-derived exosomes and their roles in the immune response under physiological and pathological conditions. The use of immunocyte exosomes in immunotherapy and vaccine development is discussed.

The usefulness of diffusion-weighted magnetic resonance (MR) imaging (DWI) for differentiating central lung cancer from postobstructive lobar collapse (POC) was investigated. Thirty-three cases suspected of lung cancer and POC on chest bolus computed tomography (CT) underwent thoracic MR imaging examinations. MR examinations were performed using a 1.5-T clinical scanner. Scanning sequences were T1-weighted imaging, T2-weighted imaging (T2WI) and DWI with b=0, 500 s/mm(2), four excitations and segmented breath-holding. The densities and signals of cancer and postobstructive collapsed lung were compared on bolus-enhanced CT, T2W and DW images. Statistical analyses were performed with chi-square test, paired t-test, non-parameter test and kappa statistics. Differentiation between cancer and POC was possible on bolus CT, T2W and DW images in 14, 21 and 26 patients, respectively. Eight cases that were impossible to differentiate on T2W images were distinguishable on DWI, demonstrating that DWI is complementary to T2WI. Using a combination of T2W and DW images, 88% (29/33) of cases were differentiated on MR imaging. Thus, a combination of T2W and DW imaging is superior to bolus-CT or T2WI alone. The contrast-to-noise ratio of DWI was significantly higher than that of T2WI. Agreement between two independent observers on the differential ability of lung cancer and POC was higher for DWI (kappa=0.474) than for T2WI (kappa=0.339). The degree of consolidation around the cancer was negatively correlated with the degree of artifact and degree of deformation. It is feasible to use DWI to differentiate lung cancer from POC. DWI played a role in confirming and providing complementary information to that obtained from T2WI. Our data indicate that using a combination of the two scanned sequences was the best means of distinguishing between lung cancer and POC.

Colorectal carcinoma is a frequent cause of cancer-related death in men and women. miRNAs (microRNAs) are endogenous small non-coding RNAs that regulate gene expression negatively at the post-transcriptional level. In the present study we investigated the possible role of microRNAs in the development of MDR (multidrug resistance) in colorectal carcinoma cells. We analysed miRNA expression levels between MDR colorectal carcinoma cell line HCT116/L-OHP cells and their parent cell line HCT116 using a miRNA microarray. miR-297 showed lower expression in HCT116/L-OHP cells compared with its parental cells. MRP-2 (MDR-associated protein 2) is an important MDR protein in platinum-drug-resistance cells and is a predicted target of miR-297. Additionally miR-297 was down-regulated in a panel of human colorectal carcinoma tissues and negatively correlated with expression levels of MRP-2. Furthermore, we found that ectopic expression of miR-297 in MDR colorectal carcinoma cells reduced MRP-2 protein level and sensitized these cells to anti-cancer drugs in vitro and in vivo. Taken together, our findings suggest that miR-297 could play a role in the development of MDR in colorectal carcinoma cells, at least in part by modulation of MRP-2.

Small-cell lung cancer (SCLC) grows rapidly and metastasizes to multiple organs. We examined the antimetastatic effects of the humanized anti-ganglioside GM2 (GM2) antibodies, BIW-8962 and KM8927, compared with the chimeric antibody KM966, in a SCID mouse model of multiple organ metastases induced by GM2-expressing SCLC cells. BIW-8962 and KM8927 induced higher antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity than KM966 against the GM2-expressing SCLC cell line SBC-3 in vitro. These humanized antibodies inhibited the production of multiple organ metastases, increased the number of apoptotic cells, and prolonged the survival of the SCID mice. Histological analyses using clinical specimens showed that SCLC cells expressed GM2. These findings suggest that humanized anti-GM2 antibodies could be therapeutically useful for controlling multiple organ metastases of GM2-expressing SCLC. (Cancer Sci 2011; 102: 2157-2163 L ung cancer is the leading cause of malignancy-related deaths worldwide.(1-3) Its high mortality rate has been attributed to its high metastatic potential to multiple organs, including the brain, liver, bones, and lymph nodes. (4,5) Metastasis to these organs frequently causes severe symptoms, such as pain, paresis, and dyspnea, and decreases patients' quality of life. (6) Approximately 15% of lung tumors are classified as small-cell lung cancer (SCLC); these tumors grow and metastasize to multiple organs much faster than non-small-cell lung cancer (NSCLC).(7) Although initially sensitive to conventional chemotherapy and radiotherapy, SCLC tumors eventually relapse and become refractory to conventional chemotherapy agents.(8) In addition, although several molecularly targeted drugs, such as the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors gefitinib and erlotinib and the angiogenesis inhibitor bevacizumab, are successful in the treatment of NSCLC, no effective molecularly targeted drugs are currently available for SCLC. Therefore, novel therapeutic methods are essential for improving the poor prognosis of patients with this disease.Ganglioside GM2 (GM2) is a glycolipid that localizes to plasma membranes and is involved in cell adhesion and signal transduction. GM2 also plays crucial roles in metastasis. (9,10) Highly metastatic tumor cells contain higher amounts of gangliosides than do tumor cells with low metastatic potential. (11,12) Moreover, normal cells such as fibroblasts and epithelial cells express little GM2, indicating that GM2 is an ideal target for antimetastatic therapy.We recently established a multiple organ metastasis model in natural killer (NK) cell-depleted SCID mice, consisting of the GM2-expressing SCLC cell line SBC-3. We found that the chimeric anti-GM2 antibody, KM966, induced antibody-dependent cellular cytotoxicity (ADCC) and inhibited multiple organ metastasis of SBC-3 cells in vivo. (13,14) Moreover, these SBC-3 cells continued to express GM2 even after becoming resistant to adriamycin. (15,16) These findings provide a therape...