Cyclin E expression in papillary thyroid carcinoma: Relation to staging

Activation of CXCL5-CXCR2 axis promotes proliferation and accelerates G1 to S phase transition of papillary thyroid carcinoma cells and activates JNK and p38 pathways

C-X-C motif chemokine ligand 5 (CXCL5) is initially identified to recruit neutrophils by interacting with its receptor, C-X-C motif chemokine receptor 2 (CXCR2). Our prior work demonstrated that the expression levels of CXCL5 and CXCR2 were higher in the papillary thyroid carcinoma (PTC) tumors than that in the non-tumors. This study was performed to further investigate how this axis regulates the growth of PTC cells. B-CPAP cells (BRAF^V600E) and TPC-1 cells (RET/PTC rearrangement) expressing CXCR-2 were used as in vitro cell models. Our results showed that the recombinant human CXCL5 (rhCXCL5) promoted the proliferation of PTC cells. rhCXCL5 accelerated the G1/S transition, upregulated the expression of a group of S (DNA synthesis) or M (mitosis)-promoting cyclins and cyclin-dependent kinases (CDKs), and downregulated CDK inhibitors in PTC cells. The CDS region of homo sapiens CXCL5 gene was inserted into an eukaryotic expression vector to mediate the overexpression of CXCL5 in PTC cells. The phosphorylation of c-Jun N-terminal kinases (JNK) and p38, and the nuclear translocation of c-Jun were enhanced by CXCL5 overexpression, whereas attenuated by CXCR2 antagonist SB225002. Additionally, CXCL5/CXCR2 axis, JNK and p38 pathway inhibitors, SB225002, SP600125 and SB203580, suppressed the growth of PTC cells overexpressing CXCL5 in nude mice, respectively. Collectively, our study demonstrates a growth-promoting effect of CXCL5-CXCR2 axis in PTC cells in vitro and in vivo.

Genetic mutations, molecular markers and future directions in research

Recent molecular studies have described a number of abnormalities associated with the pathogenesis of thyroid carcinoma. These distinct molecular events are often associated with specific stages of tumor development and may serve as prognostic factors and therapeutic targets. A better understanding of the mechanisms involved in thyroid cancer pathogenesis, will hopefully help translate these discoveries to improved patient care.

Expression of cell-cycle regulators (cyclin D1, cyclin E, p27kip1, p57kip2) in papillary thyroid carcinoma

Objective: To evaluate the expression of cell-cycle regulators in papillary thyroid carcinoma in relation to lymph node metastatic features, and to determine whether immunohistochemical staining of cell-cycle markers can predict lymph node metastasis.

Study Design: Cross-sectional study of prior surgical specimens.

Setting: Academic tertiary referral center.

Subjects and Methods: We reviewed the clinical records of patients who had undergone surgery for thyroid cancer and follicular adenoma between January 2005 and May 2008 at our clinic. Among these cases, 92 patients, comprising 28 patients with follicular adenoma, 32 with papillary thyroid carcinoma without lymph node metastasis, and 32 with papillary thyroid carcinoma with lymph node metastasis, were selected randomly. Formalin-fixed, paraffin-embedded tissues from the 92 patients were immunohistochemically stained for cyclin D1, cyclin E, p27kip1, and p57kip2, and protein expression levels were quantified and compared among the groups.

Results: Tumor specimens from the papillary thyroid carcinoma group had significantly higher expression levels of cyclin D1 and cyclin E, and cytoplasmic expression of p57kip2 than the other two groups ( P < 0.05). In particular, all malignant cases expressed cyclin D1, and cytoplasmic p57kip2 was expressed only in malignant cases. Furthermore, differences in the grade of cyclin D1 expression according to lymph node metastasis were statistically significant ( P < 0.05).

Conclusion: Our results suggest that immunohistochemistry of certain cell-cycle regulators may be helpful in the diagnosis of papillary thyroid carcinoma, and that cyclin D1 in particular may be a useful marker for evaluating lymph node metastasis.

Clinical implications of molecular markers in follicular cell-derived thyroid cancer

The increasing use/applications of molecular biology techniques have provided new insights on the genetic changes that underlie carcinogenesis and tumor progression in thyroid cancer. Molecular analysis may improve the histopathologic evaluation of follicular cell-derived thyroid carcinoma, not only elucidating some unresolved problems related to the diagnosis and disease prognosis, but also by improving patient management. Besides increasing our comprehension of cancer biology, either genetic alterations or gene expression profiles implicated in thyroid carcinogenesis shed new light on innovative diagnostic procedures as well as on targeted therapies.

Overexpression of cyclin E messenger ribonucleic acid in nasopharyngeal carcinoma correlates with poor prognosis

AIMS

S-phase kinase-associated protein 2 is required for the degradation of p27 protein, which is a negative regulator of cyclin E/cyclin-dependent kinase 2 complex. The present study examined the expression of cyclin E, S-phase kinase-associated protein 2 and p27 protein in nasopharyngeal carcinoma.

METHODS

Tissue from 35 cases of nasopharyngeal carcinoma and 10 normal nasopharyngeal tissue samples underwent reverse polymerase chain reaction to detect messenger ribonucleic acid. Immunohistochemical analysis was performed on 29 nasopharyngeal tissue samples in order to detect protein expression.

RESULTS

Messenger ribonucleic acid expression in the nasopharyngeal carcinoma tissue samples analysed indicated a 1.75-fold change in the amount of S-phase kinase-associated protein 2, a 0.34-fold change in the amount of cyclin E and a 0.31-fold change in the amount of p27 protein, compared with positive controls. High levels of cyclin E significantly correlated with late-stage nasopharyngeal carcinoma (p = 0.009) and a poor overall survival (p = 0.010). Immunohistochemical analysis indicated positive expression of S-phase kinase-associated protein 2 in 16/29 nasopharyngeal tissue samples (55 per cent), of cyclin E in 13/29 samples (45 per cent) and of p27 protein in 17/29 (59 per cent) samples.

CONCLUSIONS

Overexpression of cyclin E messenger ribonucleic acid showed an adverse prognostic significance, correlating with an advanced stage of nasopharyngeal carcinoma and a low overall survival rate.

Expression of cell cycle biomarkers and telomere length in papillary thyroid carcinoma: a comparative study between radiation-associated and spontaneous cancers

OBJECTIVE

Radiation exposure during childhood is the only well-established risk factor for papillary thyroid carcinoma (PTC). To better define the biologic profile of radiation-induced and sporadic PTC, we compared in these two groups of PTC the expression of cell cycle regulatory proteins and telomere length.

METHODS

Cell cycle markers (cyclin A, B1, D1, E, and Ki67) were evaluated on 100 PTC specimens (26 radiation-induced and 74 sporadic PTCs). The expression of cell cycle regulators was studied using immunohistochemistry; telomere length heterogeneity was studied using in situ hybridization in a subset of 16 formalin-fixed samples (8 radiation-induced and 8 sporadic PTCs).

RESULTS

At multivariate analysis, only cytoplasmic cyclin E staining was overexpressed in sporadic cases (P = 0.006). The other cell cycle markers and telomere length did not differ significantly between sporadic PTC and radiation-induced PTC.

CONCLUSIONS

These markers cannot be used to differentiate radiation-induced from sporadic PTCs.

Peroxisome proliferator-activated receptor-delta induces cell proliferation by a cyclin E1-dependent mechanism and is up-regulated in thyroid tumors

Peroxisome proliferator-activated receptors (PPARs) are lipid-sensing nuclear receptors that have been implicated in multiple physiologic processes including cancer. Here, we determine that PPARdelta induces cell proliferation through a novel cyclin E1-dependent mechanism and is up-regulated in many human thyroid tumors. The expression of PPARdelta was induced coordinately with proliferation in primary human thyroid cells by the activation of serum, thyroid-stimulating hormone/cyclic AMP, or epidermal growth factor/mitogen-activated protein kinase mitogenic signaling pathways. Engineered overexpression of PPARdelta increased thyroid cell number, the incorporation of bromodeoxyuridine, and the phosphorylation of retinoblastoma protein by 40% to 45% in just 2 days, one usual cell population doubling. The synthetic PPARdelta agonist GW501516 augmented these PPARdelta proliferation effects in a dose-dependent manner. Overexpression of PPARdelta increased cyclin E1 protein by 9-fold, whereas knockdown of PPARdelta by small inhibitory RNA reduced both cyclin E1 protein and cell proliferation by 2-fold. Induction of proliferation by PPARdelta was abrogated by knockdown of cyclin E1 by small inhibitory RNA in primary thyroid cells and by knockout of cyclin E1 in mouse embryo fibroblasts, confirming a cyclin E1 dependence for this PPARdelta pathway. In addition, the mean expression of native PPARdelta was increased by 2-fold to 5-fold (P < 0.0001) and correlated with that of the in situ proliferation marker Ki67 (R = 0.8571; P = 0.02381) in six different classes of benign and malignant human thyroid tumors. Our experiments identify a PPARdelta mechanism that induces cell proliferation through cyclin E1 and is regulated by growth factor and lipid signals. The data argue for systematic investigation of PPARdelta antagonists as antineoplastic agents and implicate altered PPARdelta-cyclin E1 signaling in thyroid and other carcinomas.

Cell cycle regulators show diagnostic and prognostic utility for differentiated thyroid cancer

BACKGROUND

Differentiated thyroid cancer (DTC) generally has a favorable outcome, but some patients develop local recurrence and/or distant metastases and ultimately die of their disease. Molecular markers that accurately predict tumor behavior are lacking. This study's aim was to ascertain the role of cell cycle regulators in predicting malignant histology and tumor behavior in DTC.

METHODS

Tissue microarrays consisting of 100 benign and 105 malignant thyroid lesions, plus 24 lymph node samples, were stained for p16, p21, p27, p53, p57, p63, cyclin D1, cyclin E, and mdm2. Statistical analysis was used to compare the expression of the markers in benign versus DTC lesions and correlate their expression with clinicopathologic characteristics.

RESULTS

p16, p21, cyclin D1, and cyclin E showed significantly (P < .001) increased expression in DTCs compared with benign thyroid lesions (54.7% vs. 5%, 71.7% vs. 38%, 87.1% vs. 45.7%, and 72.3% vs. 37.4%, respectively). There was no significant difference in expression between benign lesions and DTC for the remaining markers. p16 expression correlated significantly with extrathyroidal tumor extension (P = .02) and the presence of cancer in lymph nodes (P = .03). A total of 73% vs. 45% of the cancers of patients with and without lymph node involvement, respectively, stained positive for p16 (P = .01).

CONCLUSIONS

There is a statistically significant difference in the expression of p16, p21, cyclin D1, and cyclin E between DTCs and benign thyroid lesions, and p16 expression correlates with clinicopathologic variables predicting poor outcomes for DTC. These results suggest that evaluation of cell cycle derangement in thyroid tumors may serve as a useful tool for both DTC diagnosis and prognosis.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.

The retinoblastoma protein--from bench to bedside

The retinoblastoma tumour suppressor protein (Rb) has come a long way since its initial discovery in 1986. Encoded by the first candidate tumour suppressor gene it has emerged a versatile and context-dependent modulator of cell behaviour. Its activity is managed by signalling networks sensing intra- and extracellular cues. These cues are relayed to hold or permit inactivation of Rb by phosphorylation. Loss or mutation of the retinoblastoma gene is rare in sporadic cancers but defects in the pathways that license inactivation of Rb are found in the majority of them, suggesting that loss of Rb control is central to tumour development and arguing that its reinstatement might reverse tumour formation. Furthermore, mouse models with engineered defects in the Rb-phosphorylating kinases provide evidence that moderation of Rb inactivation may be a strategy for the prevention of tumour formation. The rationale behind these arguments, their underlying molecular concepts and strategies towards therapeutic application will be discussed.

Altered expression of cyclins and cell cycle inhibitors in papillary thyroid cancer: prognostic implications

Currently we lack biochemical or molecular markers that predict recurrence and metastases in thyroid cancer. Recent studies in a number of other human malignancies indicate that expression and/or subcellular localization of certain cell cycle regulators has prognostic utility. We have investigated the expression of cyclins D1 and E and of cyclin-dependent kinase inhibitor's p21 and p27 in papillary thyroid cancer (PTC) and correlated this with clinical/histological stage at diagnosis and with clinical outcome. PTCs were compared to normal thyroid, adenomas, and undifferentiated thyroid cancers (UTCs). Our studies indicate that PTCs and UTCs demonstrate low nuclear expression of cyclin E and p27, allowing a clear distinction between adenomas and these carcinomas (p < 0.004). A pattern of low nuclear expression of all four markers was observed in stage IV PTCs and UTCs, while stage I PTCs had low D1 and E accompanied by high p21 or p27. Expression of cytoplasmic cyclin D1 was significantly lower in stage IV PTCs and UTCs than in stage I-III PTC's (p </= 0.020), and appeared to correlate inversely with poor outcome in PTCs (p = 0.010). These studies suggest that evaluation of a panel of these markers and attention to their subcellular localization may be a useful adjunct in differentiating benign from malignant thyroid neoplasms and in predicting tumor behavior.

Patterns of Cyclin E, Retinoblastoma Protein, and p21Cip1/WAF1 Immunostaining in the Oncogenesis of Papillary Thyroid Carcinoma

Purpose: Uncontrolled cell proliferation, a hallmark of cancer, may result from an increased expression of cell cycle up-regulators, and/or from a reduced expression of cell cycle down-regulators. In the present study, we analyzed, by immunohistochemistry, the expression of a panel of three proteins: cyclin E and two cell cycle inhibitors, p21Cip1/WAF1 and retinoblastoma protein (pRb) product, in different stages of papillary thyroid carcinomas (PTC).

Experimental Design: We investigated immunostaining patterns of the proteins in question in 51 resected PTC in pathologic stages, ranging from pT1a to pT4, taking into consideration their relation to clinicohistopathologic factors.

Results: We observed a significant, progressive loss of expression of p21Cip1/WAF1 with advancing tumor grade. The differences reached values of significance between pT1a [papillary thyroid microcarcinomas (PMC)] and pT2 and between PMC and pT4 stages of PTC. pRb presented a similar immunostaining pattern to that of p21Cip1/WAF1 and the differences reached values of significance between pT1a and pT2, and between PMC and pT4 stages of PTC. The results of cyclin E immunostaining corresponded to our recently published result, and a negative correlation was observed between the immunostaining index of cyclin E and pRb.

Conclusions: The results of the present study suggest that cyclin E expression and suppression of pRb and p21Cip1/WAF1 may be characteristic patterns of immunostaining for PTC with a tendency to early metastasizing. If our results are confirmed in a larger study, the diagnostic panel, constructed of the antibodies against these proteins, may become a valuable tool in predicting the metastatic potential in PTC.