Rho family small GTPase Rif regulates Wnt5a-Ror1-Dvl2 signaling and promotes lung adenocarcinoma progression.

Rho in filopodia (Rif), a member of the Rho family of small GTPases, induces filopodia formation primarily on the dorsal surface of cells; however, its function remains largely unclear. Here, we show that Rif interacts with Ror1, a receptor for Wnt5a that can also induce dorsal filopodia. Our immunohistochemical analysis revealed a high frequency of coexpression of Ror1 and Rif in lung adenocarcinoma. Lung adenocarcinoma cells cultured on Matrigel established front-rear polarity with massive filopodia on their front surfaces, where Ror1 and Rif were accumulated. Suppression of Ror1 or Rif expression inhibited cell proliferation, survival, and invasion, accompanied by the loss of filopodia and cell polarity in vitro, and prevented tumor growth in vivo. Furthermore, we found that Rif was required to activate Wnt5a-Ror1 signaling at the cell surface leading to phosphorylation of the Wnt signaling pathway hub protein Dvl2, which was further promoted by culturing the cells on Matrigel. Our findings reveal a novel function of Rif in mediating Wnt5a-Ror1-Dvl2 signaling, which is associated with the formation of polarized filopodia on 3D matrices in lung adenocarcinoma cells.

Characterization of morphological alterations in micropapillary adenocarcinoma of the lung using an established cell line.

Micropapillary adenocarcinoma of the lung is a type of cancer associated with a poor prognosis and is characterized by the presence of tumor cells with a ring­like glandular structure floating within alveolar spaces. In the present study, the association between its morphological, biochemical and immunohistochemical characteristics, and malignancy was investigated using the KU­Lu­MPPt3 cell line established from a patient with MIP adenocarcinoma. Two subpopulations of KU­Lu­MPPt3 cells, namely adhesive (AD) and clumpy and suspended (CS) cells, were prepared and subjected to DNA microarray, reverse transcription­quantitative PCR, western blot and immunostaining analyses. Protein expression patterns were compared between the cell types and their derived tissues using immunostaining. The results revealed similar protein expression patterns between the tumor cells found in the alveolar spaces and CS cells, which exhibited morphological characteristic of MIP adenocarcinoma. Based on the results of DNA microarray analysis, the present study then focused on Akt and focal adhesion kinase (FAK), which were markedly activated in the KU­Lu­MPPt3 CS and AD cells, respectively. Following KU­Lu­MPPt3 CS cell plating onto collagen­coated culture dishes, some cells exhibited a transformation of their morphology into KU­Lu­MPPt3 AD­like cells within a few days, and their Akt and FAK activities were similar to those of the AD cells. Additionally, the inhibition of Akt and FAK activities with Akt and FAK inhibitors reduced KU­Lu­MPPt3 CS cell adhesion and proliferation. Thus, the aforementioned results indicated that the phosphorylation of FAK and Akt may play a crucial role in the regulation of KU­Lu­MPPt3 CS cell adhesion and proliferation, respectively. Furthermore, the malignant potential of MIP adenocarcinoma may be attributed to these morphological and biochemical alterations in the KU­Lu­MPPt3 cells.

Live-cell imaging and optical manipulation of Arabidopsis early embryogenesis.

Intercellular communications are essential for cell proliferation and differentiation during plant embryogenesis. However, analysis of intercellular communications in living material in real time is difficult owing to the restricted accessibility of the embryo within the flower. We established a live-embryo imaging system to visualize cell division and cell fate specification in Arabidopsis thaliana from zygote division in real time. We generated a cell-division lineage tree for early embryogenesis in Arabidopsis. Lineage analysis showed that both the direction and time course of cell division between sister cells differed along the apical-basal or radial axes. Using the Arabidopsis kpl mutant, in which single-fertilization events are frequent, we showed that endosperm development is not required for pattern formation during early embryogenesis. Optical manipulation demonstrated that damage to the embryo initial cell induces cell fate conversion of the suspensor cell to compensate for the disrupted embryo initial cell even after cell fate is specified.