Janusz A. Siedlecki

HAX-1 overexpression, splicing and cellular localization in tumors

BackgroundHAX-1 has been described as a protein potentially involved in carcinogenesis and especially metastasis. Its involvement in regulation of apoptosis and cell migration along with some data indicating its overexpression in cancer cell lines and tumors suggests that HAX-1 may play a role in neoplastic transformation. Here we present the first systematic analysis of HAX-1 expression in several solid tumors.MethodsUsing quantitative RT-PCR, we have determined the mRNA levels of HAX1 splice variant I in several solid tumors. We have also analyzed by semiquantitative and quantitative RT-PCR the expression of five HAX-1 splice variants in breast cancer samples and in normal tissue from the same individuals. Quantitative PCR was also employed to analyze the effect of estrogen on HAX1 expression in breast cancer cell line. Immunohistochemical analysis of HAX-1 was performed on normal and breast cancer samples.ResultsThe results reveal statistically important HAX1 up-regulation in breast cancer, lung cancer and melanoma, along with some minor variations in the splicing pattern. HAX-1 up-regulation in breast cancer samples was confirmed by immunohistochemical analysis, which also revealed an intriguing HAX-1 localization in the nuclei of the tumor cells, associated with strong ER status.ConclusionHAX-1 elevated levels in cancer tissues point to its involvement in neoplastic transformation, especially in breast cancer. The connection between HAX-1 nuclear location and ER status in breast cancer samples remains to be clarified.

Hairpin structure within the 3′UTR of DNA polymerase β mRNA acts as a post-transcriptional regulatory element and interacts with Hax-1

Aberrant expression of DNA polymerase β, a key enzyme involved in base excision repair, leads to genetic instability and carcinogenesis. Pol β expression has been previously shown to be regulated at the level of transcription, but there is also evidence of post-transcriptional regulation, since rat transcripts undergo alternative polyadenylation, and the resulting 3′UTR contain at least one regulatory element. Data presented here indicate that RNA of the short 3′UTR folds to form a strong secondary structure (hairpin). Its regulatory role was established utilizing a luciferase-based reporter system. Further studies led to the identification of a protein factor, which binds to this element—the anti-apoptotic, cytoskeleton-related protein Hax-1. The results of in vitro binding analysis indicate that the formation of the RNA–protein complex is significantly impaired by disruption of the hairpin motif. We demonstrate that Hax-1 binds to Pol β mRNA exclusively in the form of a dimer. Biochemical analysis revealed the presence of Hax-1 in mitochondria, but also in the nuclear matrix, which, along with its transcript-binding properties, suggests that Hax-1 plays a role in post-transcriptional regulation of expression of Pol β.

The Role of SWI/SNF Chromatin Remodeling Complexes in Hormone Crosstalk

SWI/SNF-type ATP-dependent chromatin remodeling complexes (CRCs) are evolutionarily conserved multiprotein machineries controlling DNA accessibility by regulating chromatin structure. We summarize here recent advances highlighting the role of SWI/SNF in the regulation of hormone signaling pathways and their crosstalk in Arabidopsis thaliana. We discuss the functional interdependences of SWI/SNF complexes and key elements regulating developmental and hormone signaling pathways by indicating intriguing similarities and differences in plants and humans, and summarize proposed mechanisms of SWI/SNF action on target loci. We postulate that, given their viability, several plant SWI/SNF mutants may serve as an attractive model for searching for conserved functions of SWI/SNF CRCs in hormone signaling, cell cycle control, and other regulatory pathways.

Chloroplast DNA synthesis in light and dark grown cultured Nicotiana tabacum cells as determined by molecular hybridization.

A simple method using molecular hybridization was devised to quantitatively measure chloroplast DNA synthesis in vivo. Total cellular DNA isolated from Nicotiana tabacum suspension cells, labeled with 3H-thymidine, was hybridized to nitrocellulose membrane-bound cloned chloroplast DNA (ct DNA) fragments. Colorless, dark grown N. tabacum cells were found to contain approximately 3300–4800 chloroplast genome copies per cell, whereas light grown, green cells contain about 9500–12000 chloroplast genomes per cell. This difference in ct DNA levels suggests that the chloroplast genome is somewhat amplified during growth of the cells in the light. The hybridization technique was also used to measure the efficiency of hybridization between cloned spinach ct DNA and tobacco ct DNA. The two DNAs were found to cross-hybridize with an efficiency of 69–75%.

The frequency of human papillomavirus infection in polish patients with vulvar squamous cell carcinoma.

Introduction: Vulvar cancer is a rare condition representing about 4% of all female genital tract tumors. In contrast to the established relationship of virtually all cervical cancer cases with the human papillomavirus (HPV) infection, the reported HPV positivity in vulvar carcinoma ranges widely. Methods: Using the Linear Array HPV Genotyping Test, we investigated the HPV incidence in a group of 46 Polish patients with vulvar squamous cell carcinoma (age range, 37-93 years; median age, 70.2 years) in clinical stages T1-2, N0-2, and M0. Results: The presence of HPV DNA was confirmed in 7 of 46 (15%) primary tumor samples. HPV 16 was found in 5 tumors (71%). HPVs 6 and 58 were detected in the remaining 2 cases of virus-associated tumors. Conclusions: We conclude that a fraction of cancers of vulva associated with HPV is insignificant, given the HPV prevalence of 8.6% in the Polish population aged 55 to 59 years (the oldest cohort of Polish women studied to date).

HAX‐1 is a nucleocytoplasmic shuttling protein with a possible role in mRNA processing

HAX‐1 is a multi‐functional protein that is involved in the regulation of apoptosis, cell motility and calcium homeostasis. It is also reported to bind RNA: it associates with structural motifs present in the 3′ untranslated regions of at least two transcripts, but the functional significance of this binding remains unknown. Although HAX‐1 has been detected in various cellular compartments, it is predominantly cytoplasmic. Our detailed localization studies of HAX‐1 isoforms revealed partial nuclear localization, the extent of which depends on the protein isoform. Further studies demonstrated that HAX‐1 is in fact a nucleocytoplasmic shuttling protein, dependent on the exportin 1 nuclear export receptor. Systematic mutagenesis allowed identification of the two nuclear export signals in the HAX‐1 sequence. HAX‐1 nuclear accumulation was observed after inhibition of nuclear export by leptomycin B, but also after specific cellular stress. The biological role of HAX‐1 nuclear localization and shuttling remains to be established, but the HAX‐1 transcript‐binding properties suggest that it may be connected to mRNA processing and surveillance. In this study, HAX‐1 status was shown to influence mRNA levels of DNA polymerase β, one of the HAX‐1 mRNA targets, although this effect becomes pronounced only after specific stress is applied. Moreover, HAX‐1 tethering to the reporter transcript caused a significant decrease in its expression. Additionally, the HAX‐1 co‐localization with P‐body markers, reported here, implies a role in mRNA processing. These results suggest that HAX‐1 may be involved in the regulation of expression of bound transcripts, possibly as part of the stress response.

EGFR, PIK3CA, KRAS and BRAF mutations in meningiomas

Meningiomas are among the most frequent intracranial tumors. Treatment involves surgical resection with optional subsequent radiotherapy for high-grade meningiomas or radiosurgery following incomplete tumor removal. At present, no pharmacological agents are used as treatment. The use of targeted therapies has been considered, and specific therapies, including anti-EGFR treatment, have been clinically tested. The experience from the treatment of various types of cancers shows that patient outcome depends on the mutational status of particular molecules, including epithelial growth factor receptor (EGFR), Kirsten rat sarcoma viral oncogene homolog (KRAS), v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit α (PIK3CA). Therefore, the aim of the present study was to assess the occurrence and potential use of these markers in patients with meningioma. In total, 55 formalin-fixed, paraffin-embedded meningioma samples were subjected to genomic sequencing of EGFR (exons 18–21), KRAS (exon 1), BRAF (exon 15) and PI3K (exons 9, 20). No mutations were identified in EGFR, KRAS or BRAF. Point mutations in PIK3CA were revealed in the samples of two patients with atypical and anaplastic meningiomas. Although these mutations appear to be rare, this result, along with previously reported findings, indicates that the PI3K/protein kinase B pathway may serve as a more reasonable molecular target for meningioma than EGFR.

TET2 Promoter DNA Methylation and Expression Analysis in Pediatric B-cell Acute Lymphoblastic Leukemia.

TET2 is a novel tumor suppressor gene involved in several hematological malignancies of myeloid and lymphoid origin. Besides loss-of-function mutations and deletions, hypermethylation of the CpG island at the TET2 promoter was found in human cancer. Previous analysis revealed no TET2 mutations in acute lymphoblastic leukemia (ALL). Since the TET2 promoter methylation status in pediatric ALL has not been reported, the aim of the present study was to determine if promoter hypermethylation may be a mechanism of TET2 inactivation in a group of pediatric ALL cases. Methylation of TET2 promoter region in one (1/45) ALL B-common patient was detected by methylation specific polymerase chain reaction (PCR) and subsequently analyzed by bisulfite sequencing. We found no correlation between promoter methylation and gene expression, measured by quantitative reverse transcriptase-PCR, however the level of TET2 expression in ALL group was significantly decreased compared to children’s normal peripheral blood mononuclear cells and isolated B-cells. TET2 promoter hypermethylation seems to have limited clinical relevance in childhood B-cell ALL due to its low frequency.

Lack of microsatellite instability in squamous cell vulvar carcinoma

Mutator phenotypes with microsatellite instability (MSI) are observed in a subset of solid tumors. The objective of our study was to investigate the occurrence of MSI in vulvar squamous cell carcinoma (VSCC) and a possible relation between MSI and the presence of human papilloma virus (HPV). DNA samples from 44 tissue specimens of the primary VSCC as well as from six metastatic lymph node samples were analysed and compared with matched reference DNA from blood samples. The MSI status was examined by polymerase chain reaction (PCR) using the Bethesda panel of five microsatellite markers. PCR products were analysed by fluorescent capillary electrophoresis. No microsatellite instability was detected in tumor samples or in metastatic lymph nodes from any of the VSCC patients examined. Microsatellite instability seems not to play a major role in the carcinogenesis of VSCC and is probably not associated with the HPV‐related genetic background of this neoplasm.

Mutational Analysis of Recurrent Meningioma Progressing From Atypical to Rhabdoid Subtype

BACKGROUNDnRhabdoid meningioma is rare aggressive meningioma histological subtype that develops predominantly through progression from less malignant tumors. Owing to its low incidence, this tumors biological background is unknown. The aim of this study was to profile somatic mutations in 4 meningioma samples from the same patient, derived previously from 4 subsequent tumor resections.nnnCASE DESCRIPTIONnA 58-year-old woman presented with recurrent meningioma progressing from atypical to rhabdoid subtype. Four tumor samples that represent a primary tumor (atypical GII) and 3 recurrent tumors that were subsequently removed (anaplastic GIII, rhabdoid GIII, and anaplastic/rhabdoid GIII) from this patient were subjected to mutational analysis of coding sequences of 952 tumor-related genes. Three mutations were identified in all tumor samples exhibiting a high allelic frequency: ARID1A frameshift deletion, NF2 in-frame deletion, and missense variant of SRSF2. The predicted inactivating effect of ARID1A deletion was confirmed by immunohistochemical staining of tumor sections in which a high proportion of cells lacked protein expression. Additional low-allelic-fraction mutations were observed in all tumor samples, likely representing passenger, low-effect mutations that reflect a clonal selection of tumor cells through malignant progression of the meningioma.nnnCONCLUSIONnThe mutation of ARID1A that encodes the subunit of the SWI/SNF complex represents the most likely driver of the tumors malignant potential. It also may be involved in the acquisition of the rhabdoid phenotype, given that mutations in chromatin remodeling proteins are the hallmark of atypical teratoid/rhabdoid tumors.