Tissue invasion and metastasis are leading causes of death among cancer patients due to cells escaping from the primary tumor and invading distant sites. To better understand these phenomena and develop efficient therapeutic regimens against different types of malignancies, there is a need for exclusive cellular and molecular examination of migrating cells. In this study, aggressive brain cancer cells, G55, migrating through confined microchannels were directly extracted and used for subsequent proteomic analysis via Western Blot and/or immunostaining quantification. The method was based on an engineered Polydimethylsiloxane microchannel platform that facilitated the exclusive extraction of migrating cells and their contents while preventing non-migrating (or proliferatingdenoted as 2D) cell contamination. The migrating cells in physical confinement of the microchannels were exclusively examined for their protein expression. They were found with increased expression of Vimentin, approximately 2.5-fold higher than 2D cells. On the other hand, the migrating cells showed significantly decreased β3-Tubulin and Met signal compared to 2D cells. The differences in biomarker expression between migrating cells and non-migrating cells revealed by this study provided an insight into key features of cancer invasion and metastasis. The successful outcome of this research suggests improved targets for ceasing different types of malignancies. REVISED
Uncontrolled invasive cancer cell migration is among the major challenges for the treatment and management of brain cancer. Although the genetic profiles of brain cancer cells have been well characterized, the relationship between the genetic mutations and the cells' mobility has not been clearly understood. In this study, using microfluidic devices that provide a wide range of physical confinements from 20 × 5 μm to 3 × 5 μm in cross sections, we studied the effect of physical confinement on the migratory capacity of cell lines with different types of mutations. Human glioblastoma and genetically modified mouse astrocytes were used. Human glioblastoma cells with EGFRvIII mutation were found to exhibit high degree of migratory capacity in narrow confinement. From mouse astrocytes, cells with triple mutations (p53-/- PTEN-/- BRAF) were found to exhibit the highest level of migratory capacity in narrow confinement compared to both double (p53-/- PTEN-/-) and single (p53-/-) mutant cells. Furthermore, when treating the triple mutant astrocytes with AZD-6244, an inhibitor of the RAF/MEK/ERK pathway, we found significant reduction in migration through the confined channels when compared to that of controls (83% decrease in 5 × 5 μm and 86% in 3 × 5 μm channels). Our data correlate genetic mutations from different cell lines to their motility in different degrees of confinement. Our results also suggest a potential therapeutic target such as BRAF oncogene for inhibition of brain cancer invasion.
Coordination of mitochondrial and nuclear processes is key to the cellular health; however, very little is known about the molecular mechanisms regulating nuclear-mitochondrial crosstalk. Here, we report a novel molecular mechanism controlling the shuttling of CREB (cAMP response element-binding protein) protein complex between mitochondria and nucleoplasm. We show that a previously unknown protein, herein termed as Jig, functions as a tissue-specific and developmental timing-specific coregulator in the CREB pathway. Our results demonstrate that Jig shuttles between mitochondria and nucleoplasm, interacts with CrebA protein and controls its delivery to the nucleus, thus triggering CREB-dependent transcription in nuclear chromatin and mitochondria. Ablating the expression of Jig prevents CrebA from localizing to the nucleoplasm, affecting mitochondrial functioning and morphology and leads to Drosophila developmental arrest at the early third instar larval stage. Together, these results implicate Jig as an essential mediator of nuclear and mitochondrial processes. We also found that Jig belongs to a family of nine similar proteins, each of which has its own tissue- and time-specific expression profile. Thus, our results are the first to describe the molecular mechanism regulating nuclear and mitochondrial processes in a tissue- and time-specific manner.
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