Oncogenes induce a vimentin filament collapse mediated by HDAC6 that is linked to cell stiffness

Oncogenes deregulate fundamental cellular functions, which can lead to development of tumors, tumor-cell invasion, and metastasis. As the mechanical properties of cells govern cell motility, we hypothesized that oncogenes promote cell invasion by inducing cytoskeletal changes that increase cellular stiffness. We show that the oncogenes simian virus 40 large T antigen, c-Myc, and cyclin E induce spatial reorganization of the vimentin intermediate filament network in cells. At the cellular level, this reorganization manifests as increased width of vimentin fibers and the collapse of the vimentin network. At nanoscale resolution, the organization of vimentin fibers in these oncogene-expressing cells was more entangled, with increased width of the fibers compared with control cells. Expression of these oncogenes also resulted in up-regulation of the tubulin deacetylase histone deacetylase 6 (HDAC6) and altered spatial distribution of acetylated microtubules. This oncogene expression also induced increases in cellular stiffness and promoted the invasive capacity of the cells. Importantly, HDAC6 was required and sufficient for the structural collapse of the vimentin filament network, and was required for increased cellular stiffness of the oncogene-expressing cells. Taken together, these data are consistent with the possibility that oncogenes can induce cellular stiffness via an HDAC6-induced reorganization of the vimentin intermediate filament network.Oncogenes induce major changes in cell behavior that can result in the development of tumors and tumor-cell metastases. Although expression of oncogenes promotes the ability of cells to invade the surrounding environment and to form metastases (1–3), the mechanisms behind this remain to be further elucidated. Many tumors show increased tissue stiffness, which can at least in part be explained by an increase in the stiffness of the extracellular microenvironment in tumors (4). Nonetheless, this increase in stiffness might also be due to an increase in the intrinsic stiffness of the cytoplasm of transformed cells. As the mechanical properties of cells govern their motile behavior, we hypothesized that oncogenes promote cell invasion via the control of cellular stiffness.The cell cytoskeleton is composed of actin filaments, microtubules, and intermediate filaments (IFs), and it is believed to govern the mechanical properties of cells. In particular, the actin filaments have been shown to control cell mechanics (5, 6). In addition, there are a number of observations that indicate that vimentin IFs also contribute to the mechanical properties of cells. Vimentin IFs are a major cytoskeletal component in motile mesenchymal cells and metastatic tumors of epithelial origin. Epithelial-to-mesenchymal transition (EMT) is a diagnostic marker of migration and invasion of cancer cells, and it is characterized by expression of vimentin. Vimentin IFs functionally control the cell shape changes that occur during EMT and are strongly associated with cell invasion and poor tumor prognosis (7–10). This suggests that vimentin IFs have roles in the mechanical and motile properties of cells. In vitro, the mechanical properties of IFs are clearly distinct from the actin microfilament and microtubule systems (11). Under slight deformation, IFs provide compliance to cells. However, under great stress and deformation, IFs provide cells with mechanical strength and stiffness (12, 13). Vimentin fills the entire cytoplasm, and fibroblasts from mice that lack functional vimentin are significantly more pliant than normal fibroblasts (14, 15). Taken together, these observations suggest that the vimentin IF network can contribute to the mechanical strength and stiffness of cells.In addition to the mechanical properties of individual filaments, the mechanical properties of the IF network depend equally on the geometry and bonds that link individual filaments together in a network (13). Hence, not only the presence, but also the organization of the vimentin IF network will have major effects on the mechanical properties of cells. Therefore, we set out to determine whether, and if so how, oncogenes can change the spatial organization of the vimentin IF network, cellular stiffness, and cell invasion.Simian virus 40 large T antigen (SV40T), c-Myc, and cyclin E oncogenes are all intimately linked to development and progression of tumors. The SV40T antigen induces cell transformation and promotes tumor formation in various cell systems and animal models through its ability to initiate DNA replication (16). Many cancers show defective c-Myc activity, and aberrant expression of c-Myc induces major changes in gene expression, which result in enhanced cell proliferation (17). Overexpression of cyclin E, which results in accelerated G1 progression and chromosomal instability, is seen in many different types of tumors (18).Many studies have shown that increased activity of histone deacetylase 6 (HDAC6) is intimately linked to tumor formation and the invasive capacity of tumor cells. HDAC6 is up-regulated in many tumor types, and is required for optimal tumor growth; it is also used as a marker for patient prognosis (19). In addition, the Ras oncogene requires a functional HDAC6 to transform cells, as defined through anchorage-independent cell proliferation (20). Also, whereas increased expression of HDAC6 increases the invasive phenotype of cells (21), inhibition of HDAC6 inhibits cell migration (22, 23). Together, this suggests that HDAC6 is required for the cellular changes that lead to cell transformation and tumor-cell invasion. Consequently, HDAC6 is a key target for the development of anticancer drugs (24).In the present study we analyzed how oncogenes change the organization of the vimentin IF network and how this is linked to changes in cellular stiffness and invasion. Our data indicate that oncogenes cause an HDAC6-mediated reorganization of the vimentin IF network in cells, which is accompanied by increased cellular stiffness and cell invasion.     

Functional recovery in a tendon autograft used to bridge a peripheral nerve defect.

The functional recovery was examined after two different methods had been used to bridge an extended nerve gap. A 15 mm defect in the rat sciatic nerve was repaired using a tendon autograft--a new graft material--on one side and a freeze-thawed muscle graft--a well established experimental material--on the other side. Evaluation after 12 weeks included measurements of tetanic force in the gastrocnemius muscle and computerised morphometry of the tibial nerve. The muscular tetanic force recovered to 26% and 21% of control muscles, respectively, but there were no significant differences between the two types of grafts in any of the measurements. The number of regenerated axons of the tibial nerve correlated with functional recovery as judged by muscular tetanic force in the gastrocnemius muscle. We conclude that the tendon autograft supports functional recovery, as judged by return of muscular tetanic force, to an extent comparable to that of the freeze-thawed muscle graft.     

Factors affecting attitudes towards medical abortion in Lithuania

Objective Surgical abortion in Lithuania is governed by a 1994 ministerial decree that made it legal for any woman 16 or older. This article seeks to determine the key demographic factors in Lithuanian attitudes towards medical abortion, which is currently not legal.

Methods A random sample of the adult population was asked if they supported medical abortion. The dependent variable of attitude towards medical abortion was tested against the eight independent variables reported for each respondent using Chi-square tests and odds ratios. The effects of the variables upon each other were tested with two logistic regression models.

Results Among the respondents, 62.6% supported access to medical abortion. The independent variables of urban/rural residence, employment status and educational level significantly affected opinion. Overall, education level provided the strongest odds ratio for support of medical abortion.

Conclusion The majority of the Lithuanian population supports the legalisation of medical abortion. There is somewhat less support for it in rural areas, among those who are least educated and in certain nonworking population groups. Lithuanian policy-makers should consider responding to popular sentiment and legalising medical abortion.     

Is usage of hypnotics associated with mortality?

ObjectiveTo investigate the influence of hypnotic usage on all-cause and cause-specific mortality in a middle-aged population.MethodsA cohort of 1750 men and 1773 women aged 30–65 years who responded to a postal questionnaire in 1983. The questionnaire included questions about hypnotic usage, sleep duration, sleep complaints, medical conditions, depression, demographic and life style variables. Mortality data for the period 1983–2003 were collected.ResultsRegular hypnotic usage was reported by 1.7% of men and 2.2% of women, and was associated with short sleep, sleeping difficulties, several health problems and depression. During the 20-year follow-up period 379 men (21.5%) and 278 women (15.5%) died. After adjustment for potential risk factors in multivariate analyses regular hypnotic usage was associated with significantly increased risk of all-cause mortality in men (Hazard ratios [HR], 4.54; 95% confidence interval [CI], 2.47–8.37) and in women 2.03 (95% CI, 1.07–3.86). With regard to cause-specific mortality, regular hypnotic usage in men was a risk factor for coronary artery disease death, cancer death, suicide and death from “all remaining causes.” In women it was a risk factor for suicide.ConclusionsOur results show an increased risk of all-cause mortality and cause-specific mortality in regular users of hypnotics.     

Priorities in emergency obstetric care in Bolivia––maternal mortality and near-miss morbidity in metropolitan La Paz

Objective  To document the frequency and causes of maternal mortality and severe (near-miss) morbidity in metropolitan La Paz, Bolivia.
Design  Facility-based cross-sectional study.
Setting  Four maternity hospitals in La Paz and El Alto, Bolivia, where free maternal health care is provided through a government-subsidised programme.
Population  All maternal deaths and women with near-miss morbidity.
Methods  Inclusion of near-miss using clinical and management-based criteria.
Main outcome measures  Maternal mortality ratio (MMR), severe morbidity ratio (SMR), mortality indices and proportion of near-miss cases at hospital admission.
Results  MMR was 187/100 000 live births and SMR was 50/1000 live births, with a relatively low mortality index of 3.6%. Severe haemorrhage and severe hypertensive disorders were the main causes of near-miss, with 26% of severe haemorrhages occurring in early pregnancy. Sepsis was the most common cause of death. The majority of near-miss cases (74%) were in critical condition at hospital admission and differed from those fulfilling the criteria after admission as to diagnostic categories and socio-demographic variables.
Conclusions  Pre-hospital barriers remain to be of great importance in a setting of this type, where there is wide availability of free maternal health care. Such barriers, together with haemorrhage in early pregnancy, pre-eclampsia detection and referral patterns, should be priority areas for future research and interventions to improve maternal health. Near-miss upon arrival and near-miss after arrival at hospital should be analysed separately as that provides additional information about factors that contribute to maternal ill-health.