Transcription regulation and protein subcellular localization of the truncated basic hair keratin hHb1-DeltaN in human breast cancer cells

Ectopic Expression of a Truncated Isoform of Hair Keratin 81 in Breast Cancer Alters Biophysical Characteristics to Promote Metastatic Propensity

Keratins are an integral part of cell structure and function. Here, it is shown that ectopic expression of a truncated isoform of keratin 81 (tKRT81) in breast cancer is upregulated in metastatic lesions compared to primary tumors and patient-derived circulating tumor cells, and is associated with more aggressive subtypes. tKRT81 physically interacts with keratin 18 (KRT18) and leads to changes in the cytosolic keratin intermediate filament network and desmosomal plaque formation. These structural changes are associated with a softer, more elastically deformable cancer cell with enhanced adhesion and clustering ability leading to greater in vivo lung metastatic burden. This work describes a novel biomechanical mechanism by which tKRT81 promotes metastasis, highlighting the importance of the biophysical characteristics of tumor cells.

Ectopic production of hair keratin constitutes Rushton's hyaline bodies in association with hematogenous deposits

A Rushton's hyaline body (HB) is a concretion occasionally found in odontogenic cysts. Unspecified substances produced by the lining epithelium or derived from blood components have been suggested as possible causes of HB formation, but the origin of HBs is still elusive. This study aimed to clarify the origin of HBs. Ten specimens with HBs were obtained from 400 odontogenic cysts. HBs were stained by orcein and Congo red. Immunohistochemical examination revealed that HBs were positive for hair keratin and keratin 17. Hair keratin was concentrated in HBs, and cells with hair keratin expression were hardly seen, while cells with keratin 17 expression were observed near HBs. HBs were also positive for hemoglobin alpha chain. The presence of hair keratin in HBs was confirmed by Western blot analysis. The present study suggests that HBs are formed as a consequence of two independent events: unusual alteration of epithelial differentiation so as to provide hair keratin, and hemorrhage so as to provide erythrocytic substances. Although the ectopic production of hair keratin appears more essential, our results reconcile the long-standing debate between two theories, the keratin theory versus the hematogenous theory, concluding that both substances are required for the genesis of HBs, and also suggesting that they might be novel non-pathological amyloidogenic proteins.

In silico analysis of combinatorial microRNA activity reveals target genes and pathways associated with breast cancer metastasis

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Aberrant microRNA activity has been reported in many diseases, and studies often find numerous microRNAs concurrently dysregulated. Most target genes have binding sites for multiple microRNAs, and mounting evidence indicates that it is important to consider their combinatorial effect on target gene repression. A recent study associated the coincident loss of expression of six microRNAs with metastatic potential in breast cancer. Here, we used a new computational method, miR-AT!, to investigate combinatorial activity among this group of microRNAs. We found that the set of transcripts having multiple target sites for these microRNAs was significantly enriched with genes involved in cellular processes commonly perturbed in metastatic tumors: cell cycle regulation, cytoskeleton organization, and cell adhesion. Network analysis revealed numerous target genes upstream of cyclin D1 and c-Myc, indicating that the collective loss of the six microRNAs may have a focal effect on these two key regulatory nodes. A number of genes previously implicated in cancer metastasis are among the predicted combinatorial targets, including TGFB1, ARPC3, and RANKL. In summary, our analysis reveals extensive combinatorial interactions that have notable implications for their potential role in breast cancer metastasis and in therapeutic development.

The oncogenic potential of a prostate cancer-derived androgen receptor mutant

BACKGROUND

The role of androgen receptor (AR) mutations in the initiation of prostate cancer (CaP) remains unclear. The purpose of this study was to assess the influence of an AR mutation on prostate tumorigenesis and to determine the resulting molecular alterations.

METHODS

Wild-type AR (AR(WT)) or the CaP-derived K580R AR (AR(K580R)) mutant was stably transfected into SV40-immortalized human prostate epithelial pRNS-1-1 cells that lack AR expression and fail to grow in nude mice. The ability of these AR-transfected cell lines to form tumor was investigated in vitro and in vivo. Additionally, gene expression profiling of these cell lines was performed.

RESULTS

Compared with the AR(WT), the AR(K580R) induced greater than sixfold increase in colony formation in soft agar. In vivo studies confirmed that the AR(K580R)-transfected pRNS-1-1 cells were able to form tumors in nude mice. Using a combination of microarray and RT-PCR, 29 differentially expressed genes were identified in AR(K580R) cells. It was found that silencing the expression of placental alkaline phosphatase (ALPP) that was upregulated in AR(K580R) cells resulted in significant inhibition of cell growth. Furthermore, the AR(K580R)-transfected pRNS-1-1 cells expressed markedly increased p-Akt and p-p70 S6K.

CONCLUSION

The AR(K580R) mutation promoted the malignant transformation of prostate epithelial cells. This was associated with upregulation of ALPP and subsequent activation of the Akt signaling pathway.

Upregulation of the truncated basic hair keratin 1(hHb1-?N) in carcinoma cells by Epstein-Barr virus (EBV)

To investigate the role of Epstein-Barr virus (EBV) in epithelial tumors, we compared the expression pattern of cellular genes in the EBV-infected gastric carcinoma cell line, NU-GC-3, and its uninfected control. Subtractive suppression hybridization (SSH) was combined with high-density DNA array screening to identify differentially expressed genes. We have discovered that EBV infection upregulated a truncated variant of human basic hair keratin 1 (hHb1-DeltaN), a gene that had previously been identified in metastatic breast carcinoma. We verified the differential expression of hHb1-DeltaN in 3 independent EBV-positive and -negative NU-GC-3 clones by Northern blotting. We further verified the EBV-dependent upregulation of hHb1-DeltaN in 3 other carcinoma cell lines (AGS, TWO3 and DLD1) by RT-PCR. Inhibition of CpG methylation by 5-Aza-CdR induced hHb1-DeltaN mRNA expression in the EBV-negative clones but did not alter the expression in the EBV-positive clones. The expression of hHb1-DeltaN protein was detectable by immunofluorescence and Western blotting in EBV-positive but not in EBV-negative NU-GC-3 clones after proteasome inhibitor (MG132) treatment. hHb1-DeltaN protein formed fibrous structures in the cytoplasm and accumulated in distinct nuclear bodies in the euchromatic areas of the cell nucleus. We suggest that the unstable hHb1-DeltaN protein may inhibit some of the functions of the keratin cytoskeleton and/or interfere with transcription regulation. It also may establish a link between EBV and the low differentiated or anaplastic status of the carcinomas that carry the virus.