Quantitative real-time imaging of molecular dynamics during cancer cell invasion and metastasis in vivo

Resveratrol inhibits proliferation, migration and invasion via Akt and ERK1/2 signaling pathways in renal cell carcinoma cells

Recent studies have shown that resveratrol (RES) inhibits cancer cell growth, migration and invasion. Here, we evaluated RES in two human renal cell carcinoma (RCC) cell lines, ACHN and A498. We investigated the effects of RES on proliferation, cell morphology, colony formation, migration, and invasion. We used a proliferation assay to demonstrate that RES inhibited cell growth with IC₅₀ values 132.9±1.064μM in ACHN, and 112.8±1.191μM in A498, respectively. Using inverted contrast microscopy, we showed that RES reduced cell-to-cell contact and inhibited formation of filopodia. A wound healing assay showed that RES inhibited migration of RCC cells. A Transwell assay showed that RES inhibited RCC migration and invasion. Western blot analysis showed that RES suppresses expression of N-cadherin, Vimentin, Snail, MMP-2, MMP-9, p-Akt and p-ERK1/2, but increased expression of E-cadherin and TIMP-1. In the presence of PD98059, the inhibitor of ERK1/2 pathway, we repeated all of the above experiments, showed that RES acted via the ERK1/2 pathway. Taken together, our results suggested that RES suppressed RCC cell proliferation, migration, and invasion in a concentration- and time-dependent manner. These effects likely resulted from inactivation of the Akt and ERK1/2 signaling pathways.

Advanced intravital subcellular imaging reveals vital three-dimensional signalling events driving cancer cell behaviour and drug responses in live tissue

The integration of signal transduction pathways plays a fundamental role in governing disease initiation, progression and outcome. It is therefore necessary to understand disease at the signalling level to enable effective treatment and to intervene in its progression. The recent extension of in vitro subcellular image-based analysis to live in vivo modelling of disease is providing a more complete picture of real-time, dynamic signalling processes or drug responses in live tissue. Intravital imaging offers alternative strategies for studying disease and embraces the biological complexities that govern disease progression. In the present review, we highlight how three-dimensional or live intravital imaging has uncovered novel insights into biological mechanisms or modes of drug action. Furthermore, we offer a prospective view of how imaging applications may be integrated further with the aim of understanding disease in a more physiological and functional manner within the framework of the drug discovery process.

Caught in the act: revealing the metastatic process by live imaging

The prognosis of metastatic cancer in patients is poor. Interfering with metastatic spread is therefore important for achieving better survival from cancer. Metastatic disease is established through a series of steps, including breaching of the basement membrane, intravasation and survival in lymphatic or blood vessels, extravasation, and growth at distant sites. Yet, although we know the steps involved in metastasis, the cellular and molecular mechanisms of dissemination and colonization of distant organs are incompletely understood. Here, we review the important insights into the metastatic process that have been gained specifically through the use of imaging technologies in murine, chicken embryo and zebrafish model systems, including high-resolution two-photon microscopy and bioluminescence. We further discuss how imaging technologies are beginning to allow researchers to address the role of regional activation of specific molecular pathways in the metastatic process. These technologies are shedding light, literally, on almost every step of the metastatic process, particularly with regards to the dynamics and plasticity of the disseminating cancer cells and the active participation of the microenvironment in the processes.

Photoacoustic imaging: a potential tool to detect early indicators of metastasis

The metastasis of cancer is a multistage process involving complex biological interactions and difficult to predict outcomes. Accurate assessment of the extent of metastasis is critical for clinical practice; unfortunately, medical imaging methods capable of identifying the early stages of invasion and metastasis are lacking. Photoacoustic imaging is capable of providing noninvasive, real-time imaging of significant anatomical and physiological changes. indicating the progression of cancer invasion and metastasis. Preclinically, photoacoustic methods have been used to image lymphatic anatomy, including the sentinel lymph nodes, to identify circulating tumor cells within vasculature and to detect micrometastases. Progress has begun toward the development of clinically applicable photoacoustic imaging systems to assist with the determination of cancer stage and likelihood of metastatic invasion.

Bufalin prevents the migration and invasion of T24 bladder carcinoma cells through the inactivation of matrix metalloproteinases and modulation of tight junctions

Bufalin, a cardiotonic steroid extracted from toad venom, has generally been known to possess a range of biological activities; however, only a few studies have reported the anti-metastatic activity of bufalin. In the present study, we investigated the inhibitory effects of bufalin on cell migration and invasion, two critical cellular processes that are often deregulated during metastasis, using the human bladder cancer cell line, T24. Within the concentration range that was not cytotoxic, bufalin markedly inhibited the cell motility and invasiveness of T24 cells. The inhibitory effects of bufalin on cell invasiveness were associated with the tightening of tight junctions (TJs), which was demonstrated by an increase in transepithelial electrical resistance (TER). Bufalin treatment also repressed the levels of claudin proteins (claudin-2, -3 and -4) and the major components of TJs that play key roles in the control and selectivity of paracellular transport. Furthermore, the activities of matrix metalloproteinase (MMP)‑2 and -9 in T24 cells were dose‑dependently inhibited by treatment with bufalin and this also correlated with a decrease in their mRNA and protein expression levels; however, the mRNA and protein levels of the tissue inhibitor of metalloproteinase (TIMP)‑1 and -2 were increased. In addition, these effects were related to the increased phosphorylation of the extracellular signal-regulated protein kinase (ERK) pathway. The inhibition of ERK (PD98059) significantly prevented the bufalin‑induced suppression of T24 cell migration. These findings suggest that bufalin inhibits the migration and invasion of T24 cells by modulating the activity of TJs and MMPs, possibly in association with the activation of ERK.

Imaging molecular dynamics in vivo--from cell biology to animal models

Advances in fluorescence microscopy have enabled the study of membrane diffusion, cell adhesion and signal transduction at the molecular level in living cells grown in culture. By contrast, imaging in living organisms has primarily been restricted to the localization and dynamics of cells in tissues. Now, imaging of molecular dynamics is on the cusp of progressing from cell culture to living tissue. This transition has been driven by the understanding that the microenvironment critically determines many developmental and pathological processes. Here, we review recent progress in fluorescent protein imaging in vivo by drawing primarily on cancer-related studies in mice. We emphasize the need for techniques that can be easily combined with genetic models and complement fluorescent protein imaging by providing contextual information about the cellular environment. In this Commentary we will consider differences between in vitro and in vivo experimental design and argue for an approach to in vivo imaging that is built upon the use of intermediate systems, such as 3-D and explant culture models, which offer flexibility and control that is not always available in vivo. Collectively, these methods present a paradigm shift towards the molecular-level investigation of disease and therapy in animal models of disease.

Spatial regulation of RhoA activity during pancreatic cancer cell invasion driven by mutant p53

The ability to observe changes in molecular behavior during cancer cell invasion in vivo remains a major challenge to our understanding of the metastatic process. Here, we demonstrate for the first time, an analysis of RhoA activity at a subcellular level using FLIM-FRET (fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer) imaging in a live animal model of pancreatic cancer. In invasive mouse pancreatic ductal adenocarcinoma (PDAC) cells driven by mutant p53 (p53(R172H)), we observed a discrete fraction of high RhoA activity at both the leading edge and rear of cells in vivo which was absent in two-dimensional in vitro cultures. Notably, this pool of active RhoA was absent in noninvasive p53(fl) knockout PDAC cells, correlating with their poor invasive potential in vivo. We used dasatanib, a clinically approved anti-invasive agent that is active in this model, to illustrate the functional importance of spatially regulated RhoA. Dasatanib inhibited the activity of RhoA at the poles of p53(R172H) cells in vivo and this effect was independent of basal RhoA activity within the cell body. Taken together, quantitative in vivo fluorescence lifetime imaging illustrated that RhoA is not only necessary for invasion, but also that subcellular spatial regulation of RhoA activity, as opposed to its global activity, is likely to govern invasion efficiency in vivo. Our findings reveal the utility of FLIM-FRET in analyzing dynamic biomarkers during drug treatment in living animals, and they also show how discrete intracellular molecular pools might be differentially manipulated by future anti-invasive therapies.

Metastasis: tumor cells becoming MENAcing

During breast cancer metastasis cells emigrate from the primary tumor to the bloodstream, and this carries them to distant sites where they infiltrate and sometimes form metastases within target organs. These cells must penetrate the dense extracellular matrix comprising the basement membrane of the mammary duct/acinus and migrate toward blood and lymphatic vessels, processes that mammary tumor cells execute primarily using epidermal growth factor (EGF)-dependent protrusive and migratory activity. Here, we focus on how the actin regulatory protein Mena affects EGF-elicited movement, invasion and metastasis. Recent findings indicate that, in invasive migratory tumor cells, Mena isoforms that endow heightened sensitivity to EGF and increased protrusive and migratory abilities are upregulated, whereas other isoforms are selectively downregulated. This change in Mena isoform expression enables tumor cells to invade in response to otherwise benign EGF stimulus levels and could offer an opportunity to identify metastatic risk in patients.