FUNCTIONAL AND MECHANISTIC CHARACTERIZATION OF THE NUCLEAR IMPORT RECEPTOR KARYOPHERIN-α2 IN LIVER CANCER

Exchange of macromolecules between the nucleo- and cytoplasm is provided by the nuclear transport system (NTS). Karyopherins represent essential components of NTS) by serving as nuclear transport receptors/adaptor proteins. Dysregulation of karyopherins in (hepato ) carcinogenesis, including the pivotal nuclear import factor karyopherin-α2 (KPNA2), has been previously reported. However, the functional and regulatory role of KPNA2 in hepatocellular carcinoma (HCC) remains incompletely understood. To further characterize KPNA2 in this context, mass spectrometry-based proteomics was combined with functional/mechanistic cell-based approaches and data derived from murine and human HCC samples. Quantitative mass spectrometry upon siRNA-mediated KPNA2 knockdown in HCC cells revealed the microtubule-related oncoprotein stathmin among the most downregulated proteins. KPNA2 depletion resulted in impaired colony formation and tumor cell migration in HCC cells, which could be recapitulated by direct knockdown of stathmin. Having identified stathmin as functional relevant “downstream” target of KPNA2 the underlying molecular mechanism of KPNA2-dependent stathmin regulation was dissected. Out of several candidates the transcription factors E2F1 and TFDP1 were identified as transport substrates of KPNA2 and to be retained in the cytoplasm upon KPNA2 ablation followed by reduced STMN1 expression. Finally, significant correlations of STMN1 with E2F1/TFDP1 and KPNA2 expression were found based on data derived from murine HCC models and human HCC cohorts with high KPNA2 and STMN1 expression being associated with poorer patient outcome. Taken together, these data suggest that KPNA2 regulates STMN1 by mediating nuclear import of E2F1/TFDP1 and thereby provide a functionally relevant link between the NTS and microtubule-interacting proteins in HCC. Though further studies are required, interfering with nuclear import factors such as KPNA2 could represent a promising therapeutic approach in liver cancer

Photosensitizing Medications and Skin Cancer: A Comprehensive Review

(1) The incidence of skin cancer is increasing in the United States (US) despite scientific advances in our understanding of skin cancer risk factors and treatments. In vitro and in vivo studies have provided evidence that suggests that certain photosensitizing medications (PSMs) increase skin cancer risk. This review summarizes current epidemiological evidence on the association between common PSMs and skin cancer. (2) A comprehensive literature search was conducted to identify meta-analyses, observational studies and clinical trials that report on skin cancer events in PSM users. The associated risks of keratinocyte carcinoma (squamous cell carcinoma and basal cell carcinoma) and melanoma are summarized, for each PSM. (3) There are extensive reports on antihypertensives and statins relative to other PSMs, with positive and null findings, respectively. Fewer studies have explored amiodarone, metformin, antimicrobials and vemurafenib. No studies report on the individual skin cancer risks in glyburide, naproxen, piroxicam, chlorpromazine, thioridazine and nalidixic acid users. (4) The research gaps in understanding the relationship between PSMs and skin cancer outlined in this review should be prioritized because the US population is aging. Thus the number of patients prescribed PSMs is likely to continue to rise

Karyopherin α2-dependent import of E2F1 and TFDP1 maintains protumorigenic stathmin expression in liver cancer

Background: Members of the karyopherin superfamily serve as nuclear transport receptors/adaptor proteins and provide exchange of macromolecules between the nucleo- and cytoplasm. Emerging evidence suggests a subset of karyopherins to be dysregulated in hepatocarcinogenesis including karyopherin-alpha 2 (KPNA2). However, the functional and regulatory role of KPNA2 in liver cancer remains incompletely understood. Methods: Quantitative proteomics (LC-MS/MS, similar to 1750 proteins in total) was used to study changes in global protein abundance upon siRNA-mediated KPNA2 knockdown in HCC cells. Functional and mechanistic analyses included colony formation and 2D migration assays, co-immunoprecipitation (CoIP), chromatin immunoprecipitation (ChIP), qRT-PCR, immmunblotting, and subcellular fractionation. In vitro results were correlated with data derived from a murine HCC model and HCC patient samples (3 cohorts, n > 600 in total). Results: The proteomic approach revealed the pro-tumorigenic, microtubule (MT) interacting protein stathmin (STMN1) among the most downregulated proteins upon KPNA2 depletion in HCC cells. We further observed that KPNA2 knockdown leads to reduced tumor cell migration and colony formation of HCC cells, which could be phenocopied by direct knockdown of stathmin. As the underlying regulatory mechanism, we uncovered E2F1 and TFDP1 as transport substrates of KPNA2 being retained in the cytoplasm upon KPNA2 ablation, thereby resulting in reduced STMN1 expression. Finally, murine and human HCC data indicate significant correlations of STMN1 expression with E2F1/TFPD1 and with KPNA2 expression and their association with poor prognosis in HCC patients. Conclusion: Our data suggest that KPNA2 regulates STMN1 by import of E2F1/TFDP1 and thereby provide a novel link between nuclear transport and MT-interacting proteins in HCC with functional and prognostic significance

Cellular apoptosis susceptibility (CAS) is linked to integrin β1 and required for tumor cell migration and invasion in hepatocellular carcinoma (HCC)

Importins and exportins represent an integral part of the nucleocytoplasmic transport machinery with fundamental importance for eukaryotic cell function. A variety of malignancies including hepatocellular carcinoma (HCC) show de-regulation of nuclear transport factors such as overexpression of the exportin Cellular Apoptosis Susceptibility (CAS). The functional implications of CAS in hepatocarcinogenesis remain, however, poorly understood. Here we integrated proteomics, transcriptomics and functional assays with patient data to further characterize the role of CAS in HCC. By analyzing ~ 1700 proteins using quantitative mass spectrometry in HCC cells we found that CAS depletion by RNAi leads to de-regulation of integrins, particularly down-regulation of integrin β1. Consistent with this finding, CAS knockdown resulted in substantially reduced migration and invasion of HCC cell lines as analyzed by 2D ‘scratch’ and invasion chamber assays, respectively. Supporting the potential in vivo relevance, high expression levels of CAS in HCC tissue samples were associated with macroangioinvasion and poorer patient outcome. Our data suggest a previously unanticipated link between CAS and integrin signaling which correlates with an aggressive HCC phenotype

Isotopic evidence for dietary ecology of cave lion (Panthera spelaea) in North-Western Europe: Prey choice, competition and implications for extinction

The prey choice of extinct cave lions Panthera spelaea was determined using bone collagen isotopic signatures in the Belgian Ardennes and the Swabian Jura between 40,000 and 25,000 years ago as well as in the Late-glacial of the northwestern Alp foreland and of the Paris Basin. More than 370 specimens of large carnivorous and herbivorous mammals from 25 sites coeval with cave lion were analyzed. The isotopic results point to an individualistic prey choice for cave lions, with some individuals more oriented on reindeer and others on young cave bears. The isotopic signatures and therefore dietary choice of cave lions did not overlap with those of cave hyenas, indicating competitive exclusion between the large predators. The most recent western European cave lions seem to have been consuming mainly reindeer until the local extirpation of this prey species, which coincides chronologically with their own extinction. This restricted prey choice may be involved in the extinction of this large predator in Western Europe

HELLS Is Negatively Regulated by Wild-Type P53 in Liver Cancer by a Mechanism Involving P21 and FOXM1

Simple Summary The tumor suppressor protein P53 is a major player in preventing liver cancer development and progression. In this study we could show that P53 negatively regulates the expression of Helicase, lymphoid specific (HELLS), previously described as an important pro-tumorigenic epigenetic regulator in hepatocarcinogenesis. The regulatory mechanism included induction of the P53 target gene P21 (CDKN1A) resulting in repression of HELLS via downregulation of the transcription factor Forkhead Box Protein M1 (FOXM1). Our in vitro and in vivo findings indicate an important additional aspect of the tumor suppressive function of P53 in liver cancer linked to epigenetic regulation. Abstract The major tumor suppressor P53 (TP53) acts primarily as a transcription factor by activating or repressing subsets of its numerous target genes, resulting in different cellular outcomes (e.g., cell cycle arrest, apoptosis and senescence). P53-dependent gene regulation is linked to several aspects of chromatin remodeling; however, regulation of chromatin-modifying enzymes by P53 is poorly understood in hepatocarcinogenesis. Herein, we identified Helicase, lymphoid specific (HELLS), a major epigenetic regulator in liver cancer, as a strong and selective P53 repression target within the SNF2-like helicase family. The underlying regulatory mechanism involved P53-dependent induction of P21 (CDKN1A), leading to repression of Forkhead Box Protein M1 (FOXM1) that in turn resulted in downregulation of HELLS expression. Supporting our in vitro data, we found higher expression of HELLS in murine HCCs arising in a Trp53−/− background compared to Trp53+/+ HCCs as well as a strong and highly significant correlation between HELLS and FOXM1 expression in different HCC patient cohorts. Our data suggest that functional or mutational inactivation of P53 substantially contributes to overexpression of HELLS in HCC patients and indicates a previously unstudied aspect of P53′s ability to suppress liver cancer formation