Phenotypic heterogeneity is widely observed in cancer cell populations. Here, to probe this heterogeneity, we developed an image-guided genomics technique termed spatiotemporal genomic and cellular analysis (SaGA) that allows for precise selection and amplification of living and rare cells. SaGA was used on collectively invading 3D cancer cell packs to create purified leader and follower cell lines. The leader cell cultures are phenotypically stable and highly invasive in contrast to follower cultures, which show phenotypic plasticity over time and minimally invade in a sheet-like pattern. Genomic and molecular interrogation reveals an atypical VEGF-based vasculogenesis signalling that facilitates recruitment of follower cells but not for leader cell motility itself, which instead utilizes focal adhesion kinase-fibronectin signalling. While leader cells provide an escape mechanism for followers, follower cells in turn provide leaders with increased growth and survival. These data support a symbiotic model of collective invasion where phenotypically distinct cell types cooperate to promote their escape.

Withaferin A (WFA) is purified from the plant Withania somnifera and inhibits the vimentin cytoskeleton. Vimentin overexpression in cancer correlates with metastatic disease, induction of epithelial to mesenchymal transition and reduced patient survival. As vimentin functions in cell motility, we wanted to test the hypothesis that WFA inhibits cancer metastasis by disrupting vimentin function. These data showed that WFA had weak cytotoxic and apoptotic activity at concentrations less than or equal to 500 nM, but retained potent anti-invasive activity at these low doses. Imaging of breast cancer cell lines revealed that WFA induces perinuclear vimentin accumulation followed by rapid vimentin depolymerization. A concomitant induction of vimentin ser56 phosphorylation was observed, which is consistent with vimentin disassembly. Structure activity relationships were established using a set of chemically modified WFA analogs and showed that the predicted vimentin-binding region of WFA is necessary to induce vimentin ser56 phosphorylation and for its anti-invasive activity. Pharmacokinetic studies in mice revealed that WFA reaches peak concentrations up to 2 lM in plasma with a half-life of 1.36 hr following a single 4 mg/kg dose. In a breast cancer metastasis mouse model, WFA showed dose-dependent inhibition of metastatic lung nodules and induced vimentin ser56 phosphorylation, with minimal toxicity to lung tissue. Based upon these studies, we conclude that WFA is a potent breast cancer anti-metastatic agent and the anti-metastatic activity of WFA is, at least in part, mediated through its effects on vimentin and vimentin ser56 phosphorylation.Metastatic disease is the major cause of death in almost all cancer types; however, most treatments are developed to target the primary tumor and not the metastases. This is due to metastatic cells being difficult to detect, highly aggressive, chemoresistant and experimentally challenging to model. 1 At present, there is no agent in clinical use that effectively prevents metastasis and most patients ultimately succumb to metastatic disease.The metastatic process can be broadly categorized into three stages-tumor cell invasion into surrounding tissue, intravasation into blood or lymphatic vessels and extravasation into a new host environment. These events are triggered by genetic and epigenetic alterations that transform stationary epithelial cells into migratory cells, a process termed epithelialmesenchymal transition (EMT). 2,3 Recent data suggests that cancer cells can re-trigger EMT to migrate into surrounding tissue. 3,4 A classical EMT protein is vimentin; numerous reports show that vimentin is overexpressed in invasive human tumors but is nearly undetectable in non-invasive, stationary tumors. 3,[5][6][7] Vimentin is a Type III intermediate filament 8 and its overexpression correlates with metastatic disease, EMT induction, poor prognosis and reduced patient survival. 7,[9][10][11] Similar correlations between vimentin overexpression and invasion are observed in cancer ce...

Arl2 and Arl3 are closely related members of the Arf family of regulatory GTPases that arose from a common ancestor early in eukaryotic evolution yet retain extensive structural, biochemical, and functional features. The presence of Arl3 in centrosomes, mitotic spindles, midzones, midbodies, and cilia are all supportive of roles in microtubule-dependent processes. Knockdown of Arl3 by siRNA resulted in changes in cell morphology, increased acetylation of alpha-tubulin, failure of cytokinesis, and increased number of binucleated cells. We conclude that Arl3 binds microtubules in a regulated manner to alter specific aspects of cytokinesis. In contrast, an excess of Arl2 activity, achieved by expression of the [Q70L]Arl2 mutant, caused the loss of microtubules and cell cycle arrest in M phase. Initial characterization of the underlying defects suggests a defect in the ability to polymerize tubulin in the presence of excess Arl2 activity. We also show that Arl2 is present in centrosomes and propose that its action in regulating tubulin polymerization is mediated at centrosomes. Somewhat paradoxically, no phenotypes were observed Arl2 expression was knocked down or Arl3 activity was increased in HeLa cells. We conclude that Arl2 and Arl3 have related but distinct roles at centrosomes and in regulating microtubule-dependent processes.

Quantum dot bioconjugates can be used for multiplexed and quantitative detection of tumor biomarkers in cells and tissues. This new technology should have significant impact on molecular pathology if validated with traditional techniques (such as western blotting, FISH, and IHC), and with large‐scale clinical studies. In addition, it could also become the first clinical application of quantum dots.

As genomics advances reveal the cancer gene landscape, a daunting task is to understand how these genes contribute to dysregulated oncogenic pathways. Integration of cancer genes into networks offers opportunities to reveal protein–protein interactions (PPIs) with functional and therapeutic significance. Here, we report the generation of a cancer-focused PPI network, termed OncoPPi, and identification of >260 cancer-associated PPIs not in other large-scale interactomes. PPI hubs reveal new regulatory mechanisms for cancer genes like MYC, STK11, RASSF1 and CDK4. As example, the NSD3 (WHSC1L1)–MYC interaction suggests a new mechanism for NSD3/BRD4 chromatin complex regulation of MYC-driven tumours. Association of undruggable tumour suppressors with drug targets informs therapeutic options. Based on OncoPPi-derived STK11-CDK4 connectivity, we observe enhanced sensitivity of STK11-silenced lung cancer cells to the FDA-approved CDK4 inhibitor palbociclib. OncoPPi is a focused PPI resource that links cancer genes into a signalling network for discovery of PPI targets and network-implicated tumour vulnerabilities for therapeutic interrogation.

Vimentin is an intermediate filament protein whose expression correlates with increased metastatic disease, reduced patient survival, and poor prognosis across multiple tumor types. Despite these well-characterized correlations, the molecular role of vimentin in cancer cell motility remains undefined. To approach this, we used an unbiased phosphoproteomics screen in lung cancer cell lines to discover cell motility proteins that show significant changes in phosphorylation upon vimentin depletion. We identified the guanine nucleotide exchange factor (GEF) VAV2 as having the greatest loss of phosphorylation due to vimentin depletion. Since VAV2 serves as a GEF for the small Rho GTPase Rac1, a key player in cell motility and adhesion, we explored the vimentin-VAV2 pathway as a potential novel regulator of lung cancer cell motility. We show that VAV2 localizes to vimentin positive focal adhesions (FAs) in lung cancer cells and complexes with vimentin and focal adhesion kinase (FAK). Vimentin loss impairs both pY142-VAV2 and downstream pY397-FAK activity showing that vimentin is critical for maintaining VAV2 and FAK activity. Importantly, vimentin depletion reduces the activity of the VAV2 target, Rac1, and a constitutively active Rac1 rescues defects in FAK and cell adhesion when vimentin or VAV2 is compromised. Based upon this data, we propose a model whereby vimentin promotes FAK stabilization through VAV2-mediated Rac1 activation. This model may explain why vimentin expressing metastatic lung cancer cells are more motile and invasive.

Purpose: Vimentin is an epithelial-to-mesenchymal transition (EMT) biomarker and intermediate filament protein that functions during cell migration to maintain structure and motility. Despite the abundance of clinical data linking vimentin to poor patient outcome, it is unclear if vimentin is required for metastasis or is a correlative biomarker. We developed a novel genetically engineered mouse model (GEMM) to probe vimentin in lung adenocarcinoma metastasis.Experimental Design: We used the LSL- CIPs correlate with tumor grade and are vimentin-negative and E-cadherin-positive, indicating a lack of cancer cell EMT. A similar heterotypic staining pattern was observed in human lung adenocarcinoma samples. In vitro studies show that vimentin is required for CAF motility to lead tumor cell invasion, supporting a vimentin-dependent model of collective invasion. Conclusions: These data show that vimentin is required for lung adenocarcinoma metastasis by maintaining heterotypic tumor cell-CAF interactions during collective invasion. Clin Cancer Res; 24(2); 420-32. Ó2017 AACR.

Diverse kinesin motor proteins are involved in spindle function; however, the mechanisms by which they are targeted to specific sites within spindles are not well understood. Here, we show that a fusion between yellow fluorescent protein (YFP) and a minus-end-directed Kinesin-14 (C-terminal family) from Arabidopsis, ATK5, localizes to mitotic spindle midzones and regions rich in growing plus-ends within phragmoplasts. Notably, in Arabidopsis interphase cells, YFP::ATK5 localizes to microtubules with a preferential enrichment at growing plus-ends; indicating ATK5 is a plus-end tracking protein (؉TIP). This ؉TIP activity is conferred by regions outside of the C-terminal motor domain, which reveals the presence of independent plus-end tracking and minus-end motor activities within ATK5. Furthermore, mitotic spindles of atk5 null mutant plants are abnormally broadened. Based on these data, we propose a model in which ATK5 uses plus-end tracking to reach spindle midzones, where it then organizes microtubules via minus-end-directed motor activity. INTRODUCTIONDuring cell division, the proper segregation of genetic material into daughter cells requires the action of the microtubule spindle apparatus and its associated proteins. The spindle consists of two opposing sets of microtubules oriented with the minus-ends at the poles and the plus-ends at the midzone. The midzone represents the region of overlap between the two halves of the spindle, where microtubule plus-ends terminate at chromosomal kinetochores (kinetochore microtubules) or interdigitate in an antiparallel manner with microtubules from the opposite pole (interpolar microtubules). The spindle midzone is the site of force generation during anaphase spindle elongation (Leslie and Pickett-Heaps, 1983;Khodjakov et al., 2004), and in plants it persists through telophase to form the cytokinetic microtubule apparatus, the phragmoplast (Euteneuer et al., 1982).The assembly and functioning of spindles involve the highly orchestrated activities of diverse microtubule motor proteins. Kinesins convert the energy derived from ATP hydrolysis into translational movement along microtubules (Dagenbach and Endow, 2004;Lawrence et al., 2004). Kinesin-14 family members (previously referred to as C-terminal kinesins), such as Ncd from Drosophila and Kar3p from budding yeast, are unique in that they translocate exclusively toward microtubule minus-ends (Walker et al., 1990). Several Kinesin-14 family members contain microtubule binding sites in their tail regions, which specifies the ability to carry microtubules as cargo along other microtubules; in effect, moving microtubules in relation to one another (Walczak et al., 1997;Narasimhulu and Reddy, 1998;Karabay and Walker, 1999;Matuliene et al., 1999). This finding, in conjunction with subcellular localization and loss-of-function studies, has revealed two distinct roles for Kinesin-14s in spindle functioning. The first role is inferred from studies showing that loss or depletion of various Kinesin-14 family members rescues the s...