p16INK4a downregulation is involved in immortalization of primary human prostate epithelial cells induced by telomerase

Derivation of human primary prostate epithelial cell lines by differentially targeting the CDKN2A locus along with expression of hTERT

Prostate cancer (PCa) is the most common cancer diagnosed in men worldwide and was the second leading cause of cancer-related deaths in US males in 2022. Prostate cancer also represents the second highest cancer mortality disparity between non-Hispanic blacks and whites. However, there is a relatively small number of prostate normal and cancer cell lines compared to other cancers. To identify the molecular basis of PCa progression, it is important to have prostate epithelial cell (PrEC) lines as karyotypically normal as possible. Our lab recently developed a novel methodology for the rapid and efficient immortalization of normal human PrEC that combines simultaneous CRISPR-directed inactivation of CDKN2A exon 2 (which directs expression of p16INK4A and p14ARF) and ectopic expression of an hTERT transgene. To optimize this methodology to generate immortalized lines with minimal genetic alterations, we sought to target exon 1α of the CDKN2A locus so that p16INK4A expression is ablated while the exons encoding p14ARF remains unaltered. Here we describe the establishment of two cell lines: one with the above-mentioned p16INK4A only loss, and a second line targeting both products in the CDKN2A locus. We characterize the potential lineage origin of these new cell lines along with our previously obtained clones, revealing distinct gene expression signatures. Based on the analyses of protein markers and RNA expression signatures, these cell lines are most closely related to a subpopulation of basal prostatic cells. Given the simplicity of this one-step methodology and the fact that it uses only the minimal genetic alterations necessary for immortalization, it should also be suitable for the establishment of cell lines from primary prostate tumor samples, an urgent need given the limited number of available prostate cancer cell lines.

Driving effect of P16 methylation on telomerase reverse transcriptase-mediated immortalization and transformation of normal human fibroblasts

BACKGROUND

P16 inactivation is frequently accompanied by telomerase reverse transcriptase (TERT) amplification in human cancer genomes. P16 inactivation by DNA methylation often occurs automatically during immortalization of normal cells by TERT. However, direct evidence remains to be obtained to support the causal effect of epigenetic changes, such as P16 methylation, on cancer development. This study aimed to provide experimental evidence that P16 methylation directly drives cancer development.

METHODS

A zinc finger protein-based P16-specific DNA methyltransferase (P16-Dnmt) vector containing a "Tet-On" switch was used to induce extensive methylation of P16 CpG islands in normal human fibroblast CCD-18Co cells. Battery assays were used to evaluate cell immortalization and transformation throughout their lifespan. Cell subcloning and DNA barcoding were used to track the diversity of cell evolution.

RESULTS

Leaking P16-Dnmt expression (without doxycycline-induction) could specifically inactivate P16 expression by DNA methylation. P16 methylation only promoted proliferation and prolonged lifespan but did not induce immortalization of CCD-18Co cells. Notably, cell immortalization, loss of contact inhibition, and anchorage-independent growth were always prevalent in P16-Dnmt&TERT cells, indicating cell transformation. In contrast, almost all TERT cells died in the replicative crisis. Only a few TERT cells recovered from the crisis, in which spontaneous P16 inactivation by DNA methylation occurred. Furthermore, the subclone formation capacity of P16-Dnmt&TERT cells was two-fold that of TERT cells. DNA barcoding analysis showed that the diversity of the P16-Dnmt&TERT cell population was much greater than that of the TERT cell population.

CONCLUSION

P16 methylation drives TERT-mediated immortalization and transformation of normal human cells that may contribute to cancer development.

Immortalization of human primary prostate epithelial cells via CRISPR inactivation of the CDKN2A locus and expression of telomerase

BACKGROUND

Immortalization of primary prostate epithelial cells (PrEC) with just hTERT expression is particularly inefficient in the absence of DNA tumor viral proteins or p16INK4A knockdown.

MATERIALS AND METHODS

Here, we describe the establishment of immortalized normal prostate epithelial cell line models using CRISPR technology to inactivate the CDKN2A locus concomitantly with ectopic expression of an hTERT transgene.

RESULTS

Using this approach, we have obtained immortal cell clones that exhibit fundamental characteristics of normal cells, including diploid genomes, near normal karyotypes, normal p53 and pRB cell responses, the ability to form non-invasive spheroids, and a non-transformed phenotype. Based on marker expression, these clones are of basal cell origin.

CONCLUSIONS

Use of this approach resulted in the immortalization of independent clones of PrEC that retained normal characteristics, were stable, and non-transformed. Thus, this approach could be used for the immortalization of normal primary prostate cells. This technique could also be useful for establishing cell lines from prostate tumor tissues of different tumor grades and/or from patients of diverse ethnicities to generate cell line models that facilitate the study of the molecular basis of disease disparity.

Telomerase activation in the treatment of aging or degenerative diseases: a systematic review

Telomeres are protective structures that are shortened during the lifetime, resulting in aging and degenerative diseases. Subjects experiencing aging and degenerative disorders present smaller telomeres than young and healthy ones. The size of these structures can be stabilized by telomerase, an enzyme which is inactive in adult tissues but functional in fetal and newborn tissues and adult testes and ovaries. The aim of this study was to perform a systematic review to evaluate the effect of telomerase activation in the treatment of degenerative and aging disorders. We accomplished the search using the Pubmed interface for papers published from September 1985 to April 16th, 2020. We found twenty one studies that matched our eligibility criteria. I concluded that telomerase is probably a potential and safe treatment for aging and degenerative diseases, demonstrating neither side effects nor risk of cancer in the selected studies. Further studies in humans are needed to confirm safety and efficiency of this treatment.

RecQL4-Aurora B kinase axis is essential for cellular proliferation, cell cycle progression, and mitotic integrity

Human RecQL4 helicase plays critical roles in the maintenance of genomic stability. Mutations in RecQL4 helicase results in three clinically related autosomal recessive disorders: Rothmund–Thomson syndrome (RTS), RAPADILINO, and Baller–Gerold syndrome. In addition to several premature aging features, RTS patients are characterized by aneuploidy involving either loss or gain of a single chromosome. Chromosome mosaicism and isochromosomes involving chromosomes 2, 7, and 8 have been reported in RecQL4-deficient RTS patients, but the precise role of RecQL4 in chromosome segregation/stability remains to be elucidated. Here, we demonstrate that RecQL4 physically and functionally interacts with Aurora B kinase (AURKB) and stabilizes its expression by inhibiting its ubiquitination process. Our study indicates that the N-terminus of RecQL4 interacts with the catalytic domain of AURKB. Strikingly, RecQL4 suppression reduces the expression of AURKB leading to mitotic irregularities and apoptotic cell death. RecQL4 suppression increases the proportion of cells at the G2/M phase followed by an extensive cell death, presumably owing to the accumulation of mitotic irregularities. Both these defects (accumulation of cells at G2/M phase and an improper mitotic exit to sub-G1) are complemented by the ectopic expression of AURKB. Finally, evidence is provided for the requirement of both human telomerase reverse transcriptase and RecQL4 for stable immortalization and longevity of RTS fibroblasts. Collectively, our study suggests that the RecQL4–AURKB axis is essential for cellular proliferation, cell cycle progression, and mitotic stability in human cells.

Persistent in vivo cytogenetic effects of radioiodine therapy: a 21-year follow-up study using multicolor FISH

Our previous studies demonstrated the cytogenetic effects in the peripheral blood lymphocytes of a 34-year-old male patient who received ablative radioactive 131iodine therapy (RIT) on two different occasions in 1992 and 1994. Assessment of RIT-induced chromosomal damage by the cytokinesis-blocked micronucleus assay (CBMN) showed the persistence of elevated micronucleus frequency in this patient for more than two decades since the first RIT. Subsequent cytogenetic analysis performed in 2012 revealed both stable and unstable aberrations, whose frequencies were higher than the baseline reported in the literature. Here, we report the findings of our recent cytogenetic analysis peformed in 2015 on this patient using the multicolor fluorescence in situ hybridization (mFISH) technique. Our results showed that both reciprocal and non-reciprocal translocations persisted at higher frequencies in the patient than those reported in 2012. Persistence of structural aberrations for more than two decades indicate that these aberrations might have originated from long-lived T-lymphocytes or hematopoietic stem cells. Our study suggests that the long-term persistence of chromosome translocations in circulating lymphocytes can be useful for monitoring the extent of RIT-induced chromosomal instability several years after exposure and for estimating the cumulative absorbed dose after multiple RITs for retrospective biodosimetry purposes. This is perhaps the first and longest follow-up study documenting the persistence of cytogenetic damage for 21 years after internal radiation exposure.

Implications of telomeres and telomerase in endometrial pathology

BACKGROUND

Eukaryotic chromosomal ends are linear and are protected by nucleoprotein complexes known as telomeres. The complex structural anatomy and the diverse functions of telomeres as well as the unique reverse transcriptase enzyme, telomerase that maintains telomeres are under intensive scientific scrutiny. Both are involved in many human diseases including cancer, but also in ageing and chronic disease such as diabetes. Their intricate involvement in many cellular processes and pathways is being dynamically deciphered in many organs including the endometrium. This review summarizes our current knowledge on the topic of telomeres and telomerase and their potential role in providing plausible explanations for endometrial aberrations related to common gynaecological pathologies.

OBJECTIVE AND RATIONALE

This review outlines the recent major findings in telomere and telomerase functions in the context of endometrial biology. It highlights the contemporary discoveries in hormonal regulation, normal endometrial regeneration, stem cells and common gynaecological diseases such as endometriosis, infertility, recurrent reproductive failure and endometrial cancer (EC).

SEARCH METHODS

The authors carried out systematic PubMed (Medline) and Ovid searches using the key words: telomerase, telomeres, telomere length, human telomerase reverse transcriptase, telomeric RNA component, with endometrium, hormonal regulation, endometrial stem/progenitor cells, endometrial regeneration, endometriosis, recurrent miscarriage, infertility, endometrial hyperplasia, EC and uterine cancer. Publications used in this review date from 1995 until 31st June 2016.

OUTCOMES

The human endometrium is a unique somatic organ, which displays dynamic telomerase activity (TA) related to the menstrual cycle. Telomerase is implicated in almost all endometrial pathologies and appears to be crucial to endometrial stem cells. In particular, it is vital for normal endometrial regeneration, providing a distinct route to formulate possible curative, non-hormonal therapies to treat chronic endometrial conditions. Furthermore, our current understanding of telomere maintenance in EC is incomplete. Data derived from other malignancies on the role of telomerase in carcinogenesis cannot be extrapolated to EC because unlike in other cancers, TA is already present in proliferating healthy endometrial cells.

WIDER IMPLICATIONS

Since telomerase is pivotal to endometrial regeneration, further studies elucidating the role of telomeres, telomerase, their associated proteins and their regulation in normal endometrial regeneration as well as their role in endometrial pathologies are essential. This approach may allow future development of novel treatment strategies that are not only non-hormonal but also potentially curative.

Chemopreventive effect of omega-3 polyunsaturated fatty acids and atorvastatin in rats with bladder cancer

Bladder cancer remains a huge concern for the medical community because of its incidence and prevalence rates, as well as high percentage of recurrence and progression. Omega-3 polyunsaturated fatty acids and atorvastatin proved anti-inflammatory effects through peroxisome proliferator-activated receptor gamma mechanism. However, their chemopreventive effect still remained to be examined and clarified. In this study, bladder cancer was induced in rats by the chemical carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine. Omega-3 polyunsaturated fatty acids (docosahexaenoic acid and eicosapentaenoic acid: 2:3 w/w; 1200 mg/kg) and/or atorvastatin (6 mg/kg) were given orally daily to rats for eight consecutive weeks concomitantly with N-butyl-N-(4-hydroxybutyl)nitrosamine and continued for further 4 weeks after cessation of N-butyl-N-(4-hydroxybutyl)nitrosamine administration. The histopathological examination of rat bladder revealed the presence of tumors and the absence of apoptotic bodies in sections from N-butyl-N-(4-hydroxybutyl)nitrosamine group, while tumors were absent and apoptotic bodies were clearly observed in sections from rat groups treated with omega-3 polyunsaturated fatty acids, atorvastatin, or both drugs. The study of the molecular mechanisms illustrated downregulation of COX-2 and P53 (mutant) genes and suppression of transforming growth factor beta-1 and the lipid peroxidation product malondialdehyde in serum of rats of the three treated groups. This chemopreventive effect was confirmed by and associated with lower level of bladder tumor antigen in urine. However, the combined treatment with both drugs exhibited the major protective effect and nearly corrected the dyslipidemia that has been induced by N-butyl-N-(4-hydroxybutyl)nitrosamine. Collectively, omega-3 polyunsaturated fatty acids and atorvastatin, besides having anti-inflammatory properties, proved a chemopreventive effect against bladder cancer, which nominates them to be used as adjuvant therapy with other chemotherapeutics.

Extremely stringent activation of p16INK4a prevents immortalization of uterine cervical epithelial cells without human papillomavirus oncogene expression

Cervical epithelial cell immortalization with defined genetic factors without viral oncogenes has never been reported. Here we report that HPV-negative cervical epithelial cells failed to be immortalized by telomerase activation or the combination of p53 knockdown and telomerase activation. Under those conditions, p16^INK4a expression was always elevated during the late stage of limited cell lifespan, suggesting that cervical epithelial cells possess an intrinsic property of uniquely stringent activation of p16^INK4a, which may offer an explanation for the rarity of HPV-negative cervical cancer. Combining p16^INK4a knockdown with telomerase activation resulted in efficient immortalization of HPV-negative cervical epithelial cells under ordinary culture conditions. Compared with the HPV16-E6E7-immortalized cell lines derived from the same primary cell sources, the novel HPV-negative immortalized cell lines had lower degrees of chromosomal instability, maintained more sensitive p53/p21 response to DNA damage, exhibited more stringent G2 checkpoint function, and were more resistant to replication-stress-induced genomic instability. The newly immortalized HPV-negative cervical epithelial cell lines were non-tumorigenic in nude mice. The cell lines can be used not only as much-needed HPV-negative non-malignant cell models but also as starting models that can be genetically manipulated in a stepwise fashion to investigate the roles of defined genetic alterations in the development of HPV-negative cervical cancer.

Epigenetic linkage of aging, cancer and nutrition

Epigenetic mechanisms play a pivotal role in the expression of genes and can be influenced by both the quality and quantity of diet. Dietary compounds such as sulforaphane (SFN) found in cruciferous vegetables and epigallocatechin-3-gallate (EGCG) in green tea exhibit the ability to affect various epigenetic mechanisms such as DNA methyltransferase (DNMT) inhibition, histone modifications via histone deacetylase (HDAC), histone acetyltransferase (HAT) inhibition, or noncoding RNA expression. Regulation of these epigenetic mechanisms has been shown to have notable influences on the formation and progression of various neoplasms. We have shown that an epigenetic diet can influence both cellular longevity and carcinogenesis through the modulation of certain key genes that encode telomerase and p16. Caloric restriction (CR) can also play a crucial role in aging and cancer. Reductions in caloric intake have been shown to increase both the life- and health-span in a variety of animal models. Moreover, restriction of glucose has been demonstrated to decrease the incidence of age-related diseases such as cancer and diabetes. A diet rich in compounds such as genistein, SFN and EGCG can positively modulate the epigenome and lead to many health benefits. Also, reducing the quantity of calories and glucose in the diet can confer an increased health-span, including reduced cancer incidence.

Establishment and characterization of a telomerase-immortalized canine bronchiolar epithelial cell line

Dogs are susceptible to infectious diseases that occur primarily in the respiratory tract. The airway epithelium acts as a first line of defense and is constantly exposed to microorganisms present in the environment. Respiratory epithelial cells have recently gained wide use as a cell model for studying the pathogenesis of human, murine or swine respiratory pathogen infections. However, studies of the pathogenic mechanisms of canine pathogens have been hindered by the lack of reliable respiratory cell lines. Here, we cultured primary canine bronchiolar epithelial cells (CBECs), whose characteristics were confirmed by their expression of the epithelial cell-specific marker cytokeratin 18, and have provided protocols for their isolation and ex vivo expansion. Further, we established immortalized CBECs containing the human telomerase reverse transcriptase (hTERT) gene via transfection of primary CBECs with the recombinant plasmid pEGFP-hTERT. Immortalized bronchiolar epithelial cells (hTERT-CBECs) retain the morphological and functional features of primary CBECs, as indicated by reverse transcriptase polymerase chain reaction, proliferation assays, karyotype analysis, telomerase activity assay, and Western blotting, which demonstrate that hTERT-CBECs have higher telomerase activity, an extended proliferative lifespan, and a diploid complement of chromosomes, even after Passage 50. Moreover, this cell line is not transformed, as evaluated using soft agar assays and tumorigenicity analysis in nude mice, and can therefore be safely used in future studies. The isolation and establishment of stable hTERT-CBECs is of great importance for use as an in vitro model for mechanistic studies of canine pathogenic infections.

Effects of baicalin against UVA-induced photoaging in skin fibroblasts

Ultraviolet A (UVA) radiation contributes to skin photoaging. Baicalin, a plant-derived flavonoid, effectively absorbs UV rays and has been shown to have anti-oxidant and anti-inflammatory properties that may delay the photoaging process. In the current study, cultured human skin fibroblasts were incubated with 50 μg/ml baicalin 24 hours prior to 10 J/cm(2) UVA irradiation. In order to examine the efficacy of baicalin treatment in delaying UVA-induced photoaging, we investigated aging-related markers, cell cycle changes, anti-oxidant activity, telomere length, and DNA damage markers. UVA radiation caused an increased proportion of β-Gal positive cells and reduced telomere length in human skin fibroblasts. In addition, UVA radiation inhibited TGF-β1 secretion, induced G1 phase arrest, reduced SOD and GSH-Px levels, increased MDA levels, enhanced the expression of MMP-1, TIMP-1, p66, p53, and p16 mRNA, reduced c-myc mRNA expression, elevated p53 and p16 protein expression, and reduced c-myc protein expression. Baicalin treatment effectively protected human fibroblasts from these UVA radiation-induced aging responses, suggesting that the underlying mechanism involves the inhibition of oxidative damage and regulation of the expression of senescence-related genes, including those encoding for p53, p66(Shc) and p16.

Immortalization of T-cells is accompanied by gradual changes in CpG methylation resulting in a profile resembling a subset of T-cell leukemias

We have previously described gene expression changes during spontaneous immortalization of T-cells, thereby identifying cellular processes important for cell growth crisis escape and unlimited proliferation. Here, we analyze the same model to investigate the role of genome-wide methylation in the immortalization process at different time points pre-crisis and post-crisis using high-resolution arrays. We show that over time in culture there is an overall accumulation of methylation alterations, with preferential increased methylation close to transcription start sites (TSSs), islands, and shore regions. Methylation and gene expression alterations did not correlate for the majority of genes, but for the fraction that correlated, gain of methylation close to TSS was associated with decreased gene expression. Interestingly, the pattern of CpG site methylation observed in immortal T-cell cultures was similar to clinical T-cell acute lymphoblastic leukemia (T-ALL) samples classified as CpG island methylator phenotype positive. These sites were highly overrepresented by polycomb target genes and involved in developmental, cell adhesion, and cell signaling processes. The presence of non-random methylation events in in vitro immortalized T-cell cultures and diagnostic T-ALL samples indicates altered methylation of CpG sites with a possible role in malignant hematopoiesis.

An RNA-seq-based gene expression profiling of radiation-induced tumorigenic mammary epithelial cells

Immortality and tumorigenicity are two distinct characteristics of cancers. Immortalization has been suggested to precede tumorigenesis. To understand the molecular mechanisms of tumorigenicity and cancer progression in mammary epithelium, we established a tumorigenic cell model by means of heavy-ion radiation of an immortal cell model, which was created by overexpressing the human telomerase reverse transcriptase (hTERT) in normal human mammary epithelial cells. We examined the expression profile of this tumorigenic cell line (T_hMEC) using the hTERT-overexpressing immortal cell line (I_hMEC) as a control. In-depth RNA-seq data was generated by using the next-generation sequencing (NGS) platform (Life Technologies SOLiD3). We found that house-keeping (HK) and tissue-specific (TS) genes were differentially regulated during the tumorigenic process. HK genes tended to be activated while TS genes tended to be repressed. In addition, the HK genes and TS genes tended to contribute differentially to the variation of gene expression at different RPKM (gene expression in reads per exon kilobase per million mapped sequence reads) levels. Based on transcriptome analysis of the two cell lines, we defined 7053 differentially-expressed genes (DEGs) between immortality and tumorigenicity. Differential expression of 20 manually-selected genes was further validated using qRT-PCR. Our observations may help to further our understanding of cellular mechanism(s) in the transition from immortalization to tumorigenesis.

Senescent fibroblasts promote neoplastic transformation of partially transformed ovarian epithelial cells in a three-dimensional model of early stage ovarian cancer

Most epithelial ovarian cancers are diagnosed postmenopausally, although the well-established epidemiological risk factors (parity, oral contraceptive use) are premenopausal. We hypothesized that accumulation of senescent fibroblasts, together with concomitant loss of presenescent fibroblasts within the ovarian cortex, promotes initiation and early development of ovarian cancer from ovarian surface epithelial (OSE) cells. To test this, we established immortalized OSE (IOSE) cell lines that mimic early neoplastic transformation by overexpressing the CMYC oncogene (IOSE(CMYC)) and normal ovarian presenescent (PSN) and senescent (SEN) fibroblast cell lines. We then evaluated the ability of PSN and SEN fibroblasts to transform IOSE and IOSE(CMYC) after coculture. SEN fibroblasts significantly enhanced neoplastic development of IOSE(CMYC) cells; there was an up to 15-fold increase in migration of IOSE(CMYC) cells cocultured with SEN fibroblasts compared with PSN fibroblasts. Conditioned medium from SEN fibroblasts promoted anchorage-independent growth of IOSE(CMYC) cells. We studied fibroblast-epithelial cell interactions in heterotypic three-dimensional spheroid models. Dual immunohistochemical staining of spheroids for a proliferation marker (MIB-1) and cytokeratin-18 indicated that SEN fibroblasts induce approximately a five-fold increase in proliferation of IOSE(CMYC) cells relative to cocultures with PSN fibroblasts. SEN, but not PSN fibroblasts, also induced nuclear atypia in epithelial cells in three-dimensional spheroids. These data suggest for the first time that the accumulation of senescent, or loss of presenescent fibroblasts, can promote neoplastic development of partially transformed OSE cells in vitro and illustrates the power of using three-dimensional heterotypic modeling to gain better insights into the etiology underlying the development of epithelial ovarian cancer.

Inhibitor of differentiation 1 (ID1) promotes cell survival and proliferation of prostate epithelial cells

Id1 (inhibitor of differentiation 1) is a member of the bHLH protein family. Consistent with its role in promoting proliferation and inhibiting differentiation, Id1 expression is low or negligible in normal prostate epithelial cells but is high in prostate cancer. Ectopic expression of Id1 in normal prostate epithelial cells could therefore provide a model for understanding early events involved in initiation of prostate cancer. Over-expression of Id1 immortalized but did not transform ventral prostate epithelial cells (Id1-RPE). Immortalization was associated with decreased Cdkn2a, Cdkn1a, androgen receptor and increased Tert expression. Gene expression profiling over successive doublings was used to identify transcriptomic changes involved during immortalization (Tieg, Jun, alpha actin, Klf10, Id2) and in maintaining the immortalized phenotype (Igfbp3, Igfbp5, Mmp2, Tgfb3). Network analysis indicated that Id1 promotes cancer/tumor morphology, cell cycle and epithelial to mesenchymal transition by influencing AP1, tnf, tgfβ, PdgfBB and estradiol pathways. During immortalization, the expression of majority of differentially expressed genes reduced over progressive doublings suggesting a decline in transcriptional regulatory mechanisms. The associated molecular/gene expression profile of Id1-RPE cells provides an opportunity to understand the molecular pathways associated with prostate epithelial cell survival and proliferation.

An unusual self-limited clonal Mott cell proliferation with lymphoplasmacytic lymphoma-like features in a child with the Wiskott-Aldrich syndrome and Von Recklinghausen's neurofibromatosis

Patients with the Wiskott-Aldrich syndrome are at high risk for development of lymphomas, which are predominantly extranodal and of the immunoblastic type. We present a case of a self-limited lymphoproliferation with features of lymphoplasmacytic lymphoma arising in a patient with the Wiskott-Aldrich syndrome. The patient also had stigmata of von Recklinghausen's neurofibromatosis. The tumor was composed of CD138+, IgGkappa+, CD20-, PAX-5- Mott cells and CD5-, CD10-, CD19+, CD20+, CD43- small lymphoid B-cells that partially expressed CD23. The lymphadenopathy spontaneously resolved after a period of less than a year, and the patient had remained free of detectable lymphoproliferation for almost 4 years. He then developed Burkitt's lymphoma of the left parapharyngeal space. It is remarkable that both known lymphoproliferations with features of lymphoplasmatic lymphoma arising in patients with the Wiskott-Aldrich syndrome, this one and the previously described one, have spontaneously resolved. This observation is truly intriguing and requires further clinico-pathologic studies.

Early upregulation of cyclooxygenase-2 in human papillomavirus type 16 and telomerase-induced immortalization of human esophageal epithelial cells

BACKGROUND AND AIM

Cyclooxygenase-2 (COX-2) plays an important role in the carcinogenesis of esophageal squamous cell carcinoma (ESCC). However, it is not clear whether COX-2 is involved in the early or late stage of the development of ESCC. The aim of this study was to investigate the role of COX-2 in the carcinogenesis of ESCC by an immortalized esophageal epithelial cell line.

METHODS

Human papillomavirus type 16 (HPV16)-E6/E7 and human telomerase reverse transcriptase (hTERT) transfection were used for immortalization of esophageal epithelial cells. COX-2-specific RNA interference was used for the inhibition of COX-2 expression.

RESULTS

An immortalized esophageal epithelial cell line, NE6-E6E7/hTERT, was established, which had high proliferation activity but failed to induce colony formation in soft agar. COX-2 expression was upregulated in the early process of immortalization, while COX-2 small interfering RNA (siRNA) decreased the Bcl-2 expression, increased the expression of Bax, and induced cell-cycle arrest at the G0/G1 phase in NE6-E6E7/hTERT cells. Expressions of p53, cyclinD1, and the ratio of hyperphosphorylated-RB/hypophosphorylated-RB were progressively increased after E6E7 and the subsequent hTERT transfections. These changes were accompanied by the alteration of COX-2 expression, but could be reversed by COX-2 siRNA (P < 0.05). P16 expression was significantly downregulated in NE6-E6E7 or NE6-E6E7/hTERT cells (P < 0.05), and was not affected by COX-2 siRNA.

CONCLUSIONS

Our results suggest that induction of cyclooxygenase-2 is essential in the human papillomavirus type 16 and hTERT-induced immortalization of human esophageal epithelial cells, and that COX-2 inhibition may be a potential target to block the carcinogenesis of ESCC at the precancerous stage.