Y-box binding protein-1 is an evolutionary conserved transcription and translation regulating protein that is overexpressed in various human malignancies, including breast cancer. Despite reports of YB-1 and its association with distant spread of breast cancer, the intrinsic mechanism underlying this observation remains elusive. This study investigates the role of YB-1 in mediating metastasis in highly invasive breast cancer cell lines. Silencing the YBX1 gene (which encodes the YB-1 protein) by small interfering RNA (siRNA) was performed in MDA-MB-231 and Hs578T breast cancer cell lines, followed by phenotypic assays including cell migration and invasion assays. Gene expression profiling using Affymetrix GeneChip® Human Transcriptome 2.0 array was subsequently carried out in YB-1 silenced MDA-MB-231 cells. Overexpression and silencing of YBX1 were performed to assess the expression of CORO1C, one of the differentially regulated genes from the transcriptomic analysis. A Gaussia luciferase reporter assay was used to determine if CORO1C is a putative YB-1 downstream target. siRNA-mediated silencing of CORO1C and down-regulation of YBX1 in CORO1C overexpressing MDA-MB-231 cells were performed to evaluate cell migration and invasion. Downregulation of the YB-1 protein inhibited cell migration and invasion in MDA-MB-231 breast cancer cells. Global gene expression profiling in the YBX1 silenced MDA-MB-231 cells identified differential expression of several genes, including CORO1C (which encodes for an actin binding protein, coronin-1C) as a potential downstream target of YB-1. While knockdown of YBX1 gene decreased CORO1C gene expression, the opposite effects were seen in YB-1 overexpressing cells. Subsequent verification using the reporter assay revealed that CORO1C is an indirect downstream target of YB-1. Silencing of CORO1C by siRNA in MDA-MB-231 cells was also observed to reduce cell migration and invasion. Silencing of YBX1 caused a similar reduction in CORO1C expression, concomitant with a significant decrease in migration in Hs578T cells. In coronin-1C overexpressing MDA-MB-231 cells, increased migration and invasion were abrogated by YB-1 knockdown. It would appear that YB-1 could regulate cell invasion and migration via downregulation of its indirect target coronin-1C. The association between YB-1 and coronin-1C offers a novel approach by which metastasis of breast cancer cells could be targeted and abrogated.

The invasiveness of tumour cells depends on changes in cell shape, polarity and migration. Mutant p53 induces enhanced tumour metastasis in mice, and human cells overexpressing p53R273H have aberrant polarity and increased invasiveness, demonstrating the ‘gain of function’ of mutant p53 in carcinogenesis. We hypothesize that p53R273H interacts with mutant p53‐specific binding partners that control polarity, migration or invasion. Here we analyze the p53R273H interactome using stable isotope labelling by amino acids in cell culture and quantitative mass spectrometry, and identify at least 15 new potential mutant p53‐specific binding partners. The interaction of p53R273H with one of them—nardilysin (NRD1)—promotes an invasive response to heparin binding–epidermal growth factor‐like growth factor that is p53R273H‐dependant but does not require Rab coupling protein or p63. Advanced proteomics has thus allowed the detection of a new mechanism of p53‐driven invasion.

Annexin 1 (ANXA1), the first characterized member of the annexin superfamily, is known to bind or annex to cellular membranes in a calcium-dependent manner. Besides mediating inflammation, ANXA1 has also been reported to be involved in important physiopathological implications including cell proliferation, differentiation, apoptosis, cancer, and metastasis. However, with controversies in ANXA1 expression in breast carcinomas, its role in breast cancer initiation and progression remains unclear. To elucidate how ANXA1 plays a role in breast cancer initiation, we performed stable isotope labeling of amino acids in cell culture analysis on normal mammary gland epithelial cells from ANXA1-heterozygous (ANXA1^+/−) and ANXA1-null (ANXA1^−/−) mice. Among over 4000 quantified proteins, we observed 214 up-regulated and 169 down-regulated with ANXA1^−/−. Bioinformatics analysis of the down-regulated proteins revealed that ANXA1 is potentially implicated in DNA damage response, whereas the analysis of up-regulated proteins showed the possible roles of ANXA1 in cell adhesion and migration pathways. These observations were supported by relevant functional assays. The assays for DNA damage response demonstrated an accumulation of more DNA damage with slower recovery on heat stress and an impaired oxidative damage response in ANXA1^−/− cells in comparison with ANXA1^+/− cells. Overexpressing Yes-associated protein 1 or Yap1, the most down-regulated protein in DNA damage response pathway cluster, rescued the proliferative response in ANXA1^−/− cells exposed to oxidative damage. Both migration and wound healing assays showed that ANXA1^+/− cells possess higher motility with better wound closure capability than ANXA1^−/− cells. Knocking down of β-parvin, the protein with the highest fold change in the cell adhesion protein cluster, indicated an increased cell migration in ANXA1^−/− cells. Altogether our quantitative proteomics study on ANXA1 suggests that ANXA1 plays a protective role in DNA damage and modulates cell adhesion and motility, indicating its potential role in cancer initiation as well as progression in breast carcinoma.

Hepatitis B virus (HBV) infection is a major health problem affecting about 300 million people globally. Although successful administration of a prophylactic vaccine has reduced new infections, a cure for chronic hepatitis B (CHB) is still unavailable. Current anti-HBV therapies slow down disease progression but are not curative as they cannot eliminate or permanently silence HBV covalently closed circular DNA (cccDNA). The cccDNA minichromosome persists in the nuclei of infected hepatocytes where it forms the template for all viral transcription. Interactions between host factors and cccDNA are crucial for its formation, stability, and transcriptional activity. Here, we summarize the reported interactions between HBV cccDNA and various host factors and their implications on HBV replication. While the virus hijacks certain cellular processes to complete its life cycle, there are also host factors that restrict HBV infection. Therefore, we review both positive and negative regulation of HBV cccDNA by host factors and the use of small molecule drugs or sequence-specific nucleases to target these interactions or cccDNA directly. We also discuss several reporter-based surrogate systems that mimic cccDNA biology which can be used for drug library screening of cccDNA-targeting compounds as well as identification of cccDNA-related targets.