Increased chromatin plasticity supports enhanced metastatic potential of mouse melanoma cells.

Metastasis formation is strongly dependent on the migration capabilities of tumor cells. Recently it has become apparent that nuclear structure and morphology affect the cellular ability to migrate. Previously we found that migration of melanoma cells is both associated with and dependent on global chromatin condensation. Therefore, we anticipated that tumor progression would be associated with increased chromatin condensation. Interestingly, the opposite has been reported for melanoma. In trying to resolve this contradiction, we show that during growth conditions, tumor progression is associated with global chromatin de-condensation that is beneficial for faster proliferation. However, upon induction of migration, in both low- and high-metastatic mouse melanoma cells chromatin undergoes condensation to support cell migration. Our results reveal that throughout tumor progression induction of chromatin condensation by migration signals is maintained, whereas the organization of chromatin during growth conditions is altered. Thus, tumor progression is associated with an increase in chromatin dynamics.

Localization of cofilin mRNA to the leading edge of migrating cells promotes directed cell migration.

mRNA trafficking, which enables the localization of mRNAs to particular intracellular targets, occurs in a wide variety of cells. The importance of the resulting RNA distribution for cellular functions, however, has been difficult to assess. We have found that cofilin-1 mRNA is rapidly localized to the leading edge of human lung carcinoma cells and that VICKZ family RNA-binding proteins help mediate this localization through specific interactions with the 3'UTR of cofilin mRNA. Using a phagokinetic assay for cell motility, we have been able to quantify the effect of mRNA localization on the rescue of lung carcinoma cells in which cofilin was knocked down by using short hairpin RNA (shRNA). Although restoring cofilin protein to normal endogenous levels rescues general lamellipodia formation around the periphery of the cell, only when the rescuing cofilin mRNA can localize to the leading edge is it capable of also fully rescuing directed cell movement. These results demonstrate that localization of an mRNA can provide an additional level of regulation for the function of its protein product.

Patient-derived tumor spheroid cultures as a promising tool to assist personalized therapeutic decisions in breast cancer.

Background: Breast cancer is the most common cause of cancer related deaths in women. Treatment of breast cancer has many limitations including a lack of accurate biomarkers to predict success of chemotherapy and intrinsic resistance of a significant group of patients to the gold standard of therapy. Therefore, new tools are needed to provide doctors with guidance in choosing the most effective treatment plan for a particular patient and thus to increase the survival rate for breast cancer patients. Methods: Here, we present a successful method to grow in vitro spheroids from primary breast cancer tissue. Samples were received in accordance with relevant ethical guidelines and regulations. After tissue dissociation, in vitro spheroids were generated in a scaffold-free 96-well plate format. Spheroid composition was investigated by immunohistochemistry (IHC) of epithelial [pan cytokeratin (panCK)], stromal (vimentin) and breast cancer-specific markers (ER, PR, HER2, GATA). Growth and cell viability of the spheroids were assessed upon treatment with multiple anti-cancer compounds. Student's t-test and two-way ANOVA test were used to determine statistical significance. Results: We were able to successfully grow spheroids from 27 out of 31 samples from surgical resections of breast cancer tissue from previously untreated patients. Recapitulation of the histopathology of the tissue of origin was confirmed. Furthermore, a drug panel of standard first-line chemotherapy drugs used to treat breast cancer was applied to assess the viability of the patient-derived spheroids and revealed variation between samples in the response of the spheroids to different drug treatments. Conclusions: We investigated the feasibility and the utility of an in vitro, patient-derived spheroid model for breast cancer therapy, and we conclude that spheroids serve as a highly effective platform to explore cancer therapeutics and personalized treatment efficacy. These results have significant implications for the application of this model in clinical personalized medicine.

Using Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy to distinguish between melanoma cells with a different metastatic potential.

The vast majority of cancer related deaths are caused by metastatic tumors. Therefore, identifying the metastatic potential of cancer cells is of great importance both for prognosis and for determining the correct treatment. Infrared (IR) spectroscopy of biological cells is an evolving research area, whose main aim is to find the spectral differences between diseased and healthy cells. In the present study, we demonstrate that Attenuated Total Reflection Fourier Transform IR (ATR-FTIR) spectroscopy may be used to determine the metastatic potential of cancer cells. Using the ATR-FTIR spectroscopy, we can identify spectral alterations that are a result of hydration or molecular changes. We examined two murine melanoma cells with a common genetic background but a different metastatic level, and similarly, two human melanoma cells. Our findings revealed that higher metastatic potential correlates with membrane hydration level. Measuring the spectral properties of the cells allows us to determine the membrane hydration levels. Thus, ATR-FTIR spectroscopy has the potential to help in cancer metastasis prognosis.

Shaping of interphase chromosomes by the microtubule network.

It is well established that microtubule dynamics play a major role in chromosome condensation and localization during mitosis. During interphase, however, it is assumed that the metazoan nuclear envelope presents a physical barrier, which inhibits interaction between the microtubules located in the cytoplasm and the chromatin fibers located in the nucleus. In recent years, it has become apparent that microtubule dynamics alter chromatin structure and function during interphase as well. Microtubule motor proteins transport several transcription factors and exogenous DNA (such as plasmid DNA) from the cytoplasm to the nucleus. Various soluble microtubule components are able to translocate into the nucleus, where they bind various chromatin elements leading to transcriptional alterations. In addition, microtubules may apply force on the nuclear envelope, which is transmitted into the nucleus, leading to changes in chromatin structure. Thus, microtubule dynamics during interphase may affect chromatin spatial organization, as well as transcription, replication and repair.

VICKZ proteins mediate cell migration via their RNA binding activity.

The highly conserved, RNA binding VICKZ proteins help regulate RNA localization, stability, and translation in many eukaryotes. These proteins are also required for cell migration in embryos and cultured cells. In adults, many tumors overexpress VICKZ homologs, and it has been hypothesized that the proteins can mediate cell motility and invasion. How these proteins facilitate cell movement and, in particular, whether their ability to bind RNA plays a role in their function remain unclear. Using HPLC and mass spectrometry to identify a region of Xenopus Vg1 RBP (xVICKZ3) that binds the vegetal localization element of Vg1 RNA, we generated a deletion construct that functions in a dominant-negative manner. The construct associates with full-length xVICKZ3 and severely reduces binding to target RNAs. This dominant-negative construct phenocopies the effect of down-regulating xVICKZ3 in Xenopus embryos. A corresponding deletion in the human homolog hVICKZ1 similarly functions in a dominant-negative fashion to reduce the ability of full-length hVICKZ protein to bind RNA. Expression of the dominant-negative construct in human carcinoma cells inhibits cell movement by several criteria. We conclude that the ability of VICKZ proteins to mediate cell migration, in vitro and in vivo, requires their RNA binding activity.