Ki67 in endocrine neoplasms: to count or not to count, this is the question! A systematic review from the English language literature

BACKGROUND

Endocrine neoplasms are generally slow-growing tumors that can show hormonal activity and give metastases. In most cases they are benign and clearly malignant forms are easy to diagnose. However, borderline forms may occur and be, for the pathologists, very difficult to classify. In these cases, there is a strong need to identify factors that may aid. Official classification systems for endocrine neoplasms are based on the evaluation of proliferation and, in most cases, they rely on mitotic count. In support, the study of Ki67 is carried out which, however, has not yet been included in any official classification system, except for neuroendocrine neoplasms of the gastro-entero-pancreatic tract.

PURPOSE

The aim of the present study was to investigate the proven or unproven role of Ki67 in endocrine neoplasms, in different districts, in order to bring to light the substantial differences, in terms of proliferation, existing between neoplasms so similar, but at the same time, so different.

METHODS

A thorough search of English language literature was performed, looking for articles concerning Ki67 in five endocrine neoplasms (pituitary adenomas, thyroid neoplasms, adrenocortical neoplasms, pheochromocytomas and paragangliomas).

RESULTS

From 2170, 236 articles were selected and it was seen that the endocrine neoplasm in which Ki67 was most studied was the pituitary, where it still shows a controversial role. In other neoplasms different roles were identified.

CONCLUSION

The pathologist should be aware of the contribution that this proliferative marker can give to the diagnosis and, sometimes, to the therapy selection, for the clinician.

Identification of Nascent Memory CD8 T Cells and Modeling of Their Ontogeny

Primary immune responses generate short-term effectors and long-term protective memory cells. The delineation of the genealogy linking naive, effector, and memory cells has been complicated by the lack of phenotypes discriminating effector from memory differentiation stages. Using transcriptomics and phenotypic analyses, we identify Bcl2 and Mki67 as a marker combination that enables the tracking of nascent memory cells within the effector phase. We then use a formal approach based on mathematical models describing the dynamics of population size evolution to test potential progeny links and demonstrate that most cells follow a linear naive→early effector→late effector→memory pathway. Moreover, our mathematical model allows long-term prediction of memory cell numbers from a few early experimental measurements. Our work thus provides a phenotypic means to identify effector and memory cells, as well as a mathematical framework to investigate their genealogy and to predict the outcome of immunization regimens in terms of memory cell numbers generated.

The role of Ki-67 in women with a resistant prolactinoma: a retrospective analysis in 199 hospitalized patients over a period of 5 years

Proliferation-associated antigen Ki-67 is used for the histological evaluation of different tumors. Few studies have been conducted on women with a resistant prolactinoma. To better define the characteristics and to evaluate the differences between patients with different Ki-67 labeling index (LI), a retrospective study was designed to recruit 199 females with a resistant prolactinoma. The patients were divided into two groups, patients with Ki-67 LI≥3% and patients with Ki-67 LI<3%. Tumors in the LI>3% group were also larger (p=0.043), had a higher rate of invasion (p=0.014), and were associated with more frequent polyuria and polydipsia (p=0.008) compared to the LI<3% group. The pre- and post-operative PRL levels in the LI>3% group remained significantly higher compared to patients with LI<3% (p<0.05). The incidences of transient diabetes insipidus and hyponatremia in the LI>3% group were also significantly higher (p=0.037, p=0.041). Additionally, the postoperative PRL normalization rate was lower in patients with LI>3% compared with patients with LI<3% (p=0.028). The recurrence rate in the LI>3% and LI<3% groups were 27.27% and 8.47%, respectively. In conclusion, high Ki-67 LI is predictive sign of a poor prognosis in women with resistant prolactinoma.

FOXL2 suppresses proliferation, invasion and promotes apoptosis of cervical cancer cells

FOXL2 is a transcription factor that is essential for ovarian function and maintenance, the germline mutations of which give rise to the blepharophimosis ptosis epicanthus inversus syndrome (BPES), often associated with premature ovarian failure. Recently, its mutations have been found in ovarian granulosa cell tumors (OGCTs). In this study, we measured the expression of FOXL2 in cervical cancer by immunohistochemistry and its mRNA level in cervical cancer cell lines Hela and Siha by RT-PCR. Then we overexpressed FOXL2 in Hela cells and silenced it in Siha cells by plasmid transfection and verified using western blotting. When FOXL2 was overexpressed or silenced, cells proliferation and apoptosis were determined by Brdu assay and Annexin V/PI detection kit, respectively. In addition, we investigated the effects of FOXL2 on the adhesion and invasion of Hela and Siha cells. Finally, we analyzed the influences of FOXL2 on Ki67, PCNA and FasL by flow cytometry. The results showed that FOXL2 was highly expressed in cervical squamous cancer. Overexpressing FOXL2 suppressed Hela proliferation and facilitated its apoptosis. Silencing FOXL2 enhanced Siha proliferation and inhibited its apoptosis. Meanwhile, silencing FOXL2 promoted Siha invasion, but it had no effect on cells adhesion. In addition, overexpressing FOXL2 decreased the expression of Ki67 in Hela and Siha cells. Therefore, our results suggested that FOXL2 restrained cells proliferation and enhanced cells apoptosis mainly through decreasing Ki67 expression.

The pathogenesis of endometrial polyps: a systematic semi-quantitative review

The pathogenesis and natural history of endometrial polyps are not very clear. The objective of this study was to assess the opinions of international medical literature regarding the factors involved in the pathogenesis of endometrial polyps and to organize the results consistently with what is known about endometrial physiology.

MATERIALS AND METHODS

A systematic review was carried out with the following search engines: PubMed, OVID, Scopus, SCIELO, and AJOL. Two hundreds forty-six abstracts were selected from the literature; of these abstracts, 58 factors were extracted and set as causative, non-causative, unclear or protective link with endometrial polyps. This relation is described through a correspondence analysis and tested with a main effect hierarchical log-linear model.

RESULTS

The log-linear model resulted significant for the correspondence found with the following factors: (i) causative link (ageing, bcl-2 protein, excess weight/obesity, tamoxifen regardless of timing, relationship between estrogen receptors and prog-estinics, unbalanced estrogen therapy, estrogen-like effect, and unbalance between estrogens and progestinics), (ii) protective link (progestinics, antiestrogenic action), (iii) unclear link (menopause, ki-67 protein, angiogenesis, tamoxifen for a short time, tamoxifen for a long time, hormone replacement therapy (HRT), endometritis/inflammation), and (iv) non-causative link (none of the factors specifically).

DISCUSSION

Subsequently to a review of the physiology of the endometrium, the onsetting of endometrial polyps was suggested through estrogen-related and non-estrogen related ways; the two ways can overlap. The most implied factors in the development of endometrial polyps are linked with one of these or both ways.

Functional waning of naturally occurring CD4+ regulatory T-cells contributes to the onset of autoimmune diabetes

OBJECTIVE

In this study, we asked whether a possible quantitative or qualitative deficiency in naturally occurring Foxp3(+)CD4(+) regulatory T-cells (nT(reg)), which display potent inhibitory effects on T-cell functions in vitro and in vivo, may predispose to the development of type 1 diabetes.

RESEARCH DESIGN AND METHODS

We assessed the frequency and function of Foxp3(+) nT(reg) cells in primary and secondary lymphoid tissues in the NOD animal model of type 1 diabetes.

RESULTS

We show that the cellular frequency of Foxp3(+) nT(reg) cells in primary and secondary lymphoid tissues is stable and does not decline relative to type 1 diabetes-resistant mice. We show that thymic and peripheral CD4(+)CD25(+) T-cells are fully functional in vivo. We also examined the functional impact of CD4(+)Foxp3(+) nT(reg) cells on the development of autoimmune diabetes, and we demonstrate that nT(reg) cells do not affect the initial priming or expansion of antigen-specific diabetogenic T-cells but impact their differentiation in pancreatic lymph nodes. Moreover, CD4(+)Foxp3(+) nT(reg) cells also regulate later events of diabetogenesis by preferentially localizing in the pancreatic environment where they suppress the accumulation and function of effector T-cells. Finally, we show that the nT(reg) cell functional potency and intra-pancreatic proliferative potential declines with age, in turn augmenting diabetogenic responses and disease susceptibility.

CONCLUSIONS

This study demonstrates that Foxp3-expressing nT(reg) cells in NOD mice regulate diabetogenesis, but temporal alterations in nT(reg) cell function promote immune dysregulation and the onset of spontaneous autoimmunity.

Foot shock stress prolongs the telogen stage of the spontaneous hair cycle in a non-depilated mouse model

BACKGROUND

There is an increasing evidence to indicate that stress can influence skin disease and cutaneous functions. Previous studies have shown that stress alters the murine hair cycle; however, these studies have been carried out by using mouse models in which the hair cycle is forcibly synchronized after depilation.

OBJECTIVE

To examine whether foot shock stress (FS) changes the spontaneous hair cycle in a non-depilated animal model, and to evaluate the role of mast cells and substance P (SP) in the influence of stress on the hair cycle.

METHODS

Changes in the spontaneous hair cycle and the inhibitory effects of a specific SP NK1 receptor antagonist were examined in non-depilated mice during 3-4 weeks of FS.

RESULTS

Foot shock stress prolonged the telogen stage of the hair cycle and delayed the induction of the subsequent anagen stage in the animal model. FS caused an increase in the ratio of de-granulated mast cells in the skin, an increase in the number of TUNEL-positive cells, and a decrease in the number of Ki67-positive cells. The NK1 receptor antagonist, WIN 62577, inhibited these stress responses.

CONCLUSION

Our results strongly support previous work, demonstrating that stress alters active hair-cycling in vivo through the action of SP.

Ki-67 is an independent predictor of bladder cancer outcome in patients treated with radical cystectomy for organ-confined disease

PURPOSE

To determine the association of the cell proliferative marker Ki-67 with pathologic features and disease prognosis in patients with transitional cell carcinoma (TCC) of the urinary bladder.

METHODS

Immunohistochemical staining for Ki-67 was done on serial cuts from tissue microarrays containing cystectomy specimens from 9 patients without bladder cancer and 226 consecutive patients with bladder TCC. We also assessed malignant lymph nodes from 50 of the 226 cystectomy patients.

RESULTS

Ki-67 expression was increased in 42.5% cystectomy specimens and in 54% metastatic lymph nodes. In contrast, it was absent in all nine benign cystectomy specimens. Ki-67 overexpression was associated with advanced pathologic stage, higher grade, lymphovascular invasion, and metastases to lymph nodes (P = 0.001, 0.040, 0.031, and 0.036, respectively). In multivariate analyses, pathologic stage and lymph node metastases were independent predictors of disease recurrence and bladder cancer-specific mortality. In the subgroup of patients with organ-confined disease (<pT(3) N(0); n = 91), excluding patients who received neoadjuvant or adjuvant chemotherapy, Ki-67 status was an independent predictor of both disease recurrence (risk ratio, 7.591; P = 0.001) and bladder cancer-specific mortality (risk ratio, 4.045; P = 0.041).

CONCLUSIONS

Ki-67 overexpression is associated with features of aggressive bladder TCC and adds independent prognostic information to standard pathologic features for prediction of clinical outcome after radical cystectomy.

Expression of epidermal growth factor receptor and proliferative activity of cyst epithelium in human renal cystic diseases

Pathogenesis of malignancies in patients with polycystic kidney disease (PKD) is not clearly understood. Epidermal growth factor receptor (EGF-r) production by mature kidney plays a role in promotion of epithelial hyperplasia and cyst formation, its involvement in further progression is however not proven. Ki-67 is a marker for cellular proliferation. We assessed immunohistochemical expression of EGF-r and Ki-67 in epithelium of normal kidney, single cysts without PKD, epithelial tubular cells lining simple cysts and cysts with papillary proliferation in PKD patients, and analyzed the relationship with the occurrence of malignant tumors in these cases. 72% of PKD displayed EGF-r staining in epithelium lining cysts versus 33% in normal epithelium and 70% in epithelium of normal kidney. Ki-67 was increased in papillary cystic epithelium (24%) and in cysts lined by flat epithelium (66%). Renal cancers in PKD showed EGF-r staining in 33%, but no Ki-67 expression. EGF-r function and proliferative activity in cyst formation in PKD remains to be explored. EGF-r and Ki-67 expressions are not predictive of development of carcinoma in PKD.

Treatment with vector-expressed small hairpin RNAs against Ki67 RNA-induced cell growth inhibition and apoptosis in human renal carcinoma cells

Short hairpin RNAs (shRNAs) transcribed by RNA polymerase III promoters can trigger sequence-selective gene silencing in mammalian cells. By virtue of their excellent function in knocking down expression of cancer-associated genes, shRNAs could be used as new therapeutic agents for cancer. As overexpression of Ki67 in renal cancer has been correlated to a more aggressive tumor phenotype, inhibition of Ki67 protein expression by means of shRNAs seems to be a promising approach for the therapy of renal cancer. In this study, we constructed an expression plasmid encoding shRNAs against the Ki67 gene, named pSilencerKi67, and transfected it into human renal carcinoma cells. The pSilencerKi67 was shown to significantly knock down the expression of the Ki67 gene in human renal carcinoma cells, resulting in inhibiting proliferation and inducing apoptotic cell death that can be maintained for at least 6 d. These findings offer the promise of using vector-based shRNAs against Ki67 in renal cancer gene therapy.

Parathyroid growth and regression in experimental uremia

Early 1,25-dihydroxyvitamin D(3) (VD(3)) therapy during the course of renal failure prevents the downregulation of VD(3) receptor (VDR), calcium-sensing receptor (CaSR) or p21, and the parathyroid (PT) growth. We hypothesized that VD(3) could restore the decreased expressions of VDR and CaSR, and cause regression in enlarged PT glands. 5/6 nephrectomized rats fed high-phosphorus diet were killed at 1, 3, 5, or 7 days and at 2, 3, 4, 8, or 12 weeks. VD(3)-treated rats were given VD(3) intraperitoneally for 1, 2, 3, or 4 weeks, starting 8 weeks after 5/6 nephrectomy. PT glands were weighed and subjected to immunohistochemical analyses for VDR, CaSR, p21, Ki67, and Tdt-mediated dUTP nick end-labeling (TUNEL) assay. The area per cell was measured as the parameter of cell size. The expression of VDR and p21 began to decrease at day 1, and Ki67 increased at day 3, but decreased thereafter. There was a significant increase in PT gland weight to week 12 with the increase of cell size. VD(3) treatment significantly increased both VDR and CaSR expressions 2 weeks after the start of injection, and reduced the PT gland weight at week 3 with significant increase of TUNEL-positive cells and decrease of cell size. Our results suggest that PT growth in uremic rats involves both PT cell proliferation and hypertrophy, in association with the reduction of VDR, CaSR, and p21 expressions. In addition, VD(3) treatment could reverse PT hyperplasia and hypertrophy via restoration of these proteins.

Early loss of proliferative potential of human peritoneal mesothelial cells in culture: the role of p16INK4a-mediated premature senescence

Much has been learned about the mechanisms underlying cellular senescence. The pathways leading to senescence appear to vary, depending on the cell type and cell culture conditions. In this respect, little is known about senescence of human peritoneal mesothelial cells (HPMC). Previous studies have significantly differed in the reported proliferative lifespan of HPMC. Therefore, in the present study, we have examined how HPMC enter state of senescence under conditions typically used for HPMC culture. HPMC were isolated from omentum and grown into senescence. The cultures were assessed for the growth rate, the presence of senescence markers, activation of cell-cycle inhibitors, and the oxidative stress. HPMC were found to reach, on average, six population doublings before senescence. The terminal growth arrest was associated with decreased expression of Ki67 antigen, increased percentage of cells in the G1 phase, reduced early population doubling level cDNA-1 mRNA expression, and the presence of senescence-associated beta-galactosidase. Compared with early-passage cells, the late-passage HPMC exhibited increased expression of p16INK4a but not of p21Cip1. In addition, these cells generated more reactive oxygen species and displayed increased presence of oxidatively modified DNA (8-hydroxy-2'-deoxyguanosine). These results demonstrate that early onset of senescence in omentum-derived HPMC may be associated with oxidative stress-induced upregulation of p16INK4a.

Prognostic Factors in Stage T1 Grade 3 Bladder Cancer Survival: The Role of G1–S Modulators (p53, p21Waf1, p27kip1, Cyclin D1, and Cyclin D3) and Proliferation Index (ki67-MIB1)

OBJECTIVE

To determine the prognostic value of a subset of regulators of the transition from G1-to-S phase of cell cycle in stage T1 grade 3 bladder cancers.

METHODS

Fifty-one such cases were investigated to determine the significance on patient's survival of p53, p21Waf1, p27Kip1, Cyclin D1, Cyclin D3, and ki67-MIB1 (proliferation index). The statistical analysis included Kaplan-Meier methodology with Log-rank test and Cox' proportional hazard analysis.

RESULTS

Tumor size (p=0.0034), and the labeling index of ki67-MIB1 (p=0.0034), p53 (p=0.0332), p27kip1 (p=0.0059) and Cyclin D1 (p=0.0103) were associated to disease-free survival. Progression-free survival was related to tumor size (p<0.0001), ki67 (p=0.0163), p53 (p=0.0041), p27kip1 (p=0.0161), Cyclin D1 (p<0.0001) and Cyclin D3 (p<0.0001). Patient's overall survival was associated to Cyclin D3 (p<0.0001), p53 (p=0.0017), p21Waf1 (p=0.0142), Cyclin D1 (p<0.0001), ki67-MIB1 (p=0.0450), and tumor size (p=0.0296). Down-regulation of p27kip1 and Cyclin D3 over-expression (disease-free), over-expression of p53, Cyclin D1 and Cyclin D3 (progression-free), and over-expression of Cyclin D3 (overall survival) were independent predictors by Cox's multivariate analysis. Down-regulation of p27kip1 (p<0.001, R.R. 0.997, 95%C.I. 0.995-0.999), and over-expression of Cyclin D1 (p<0.001, R.R. 1.009, 95%C.I. 1.004-1.014) and Cyclin D3 (p=0.005, R.R. 1.013, 95%C.I. 1.004-1.022) were the main independent predictors.

CONCLUSION

Down-regulation of p27kip1 and over-expression of Cyclin D1 and Cyclin D3 might be relevant predictors of survival in stage T1 grade 3 bladder cancers, thus selecting a group of patients at higher risk of malignant behavior.

The proliferation marker pKi-67 organizes the nucleolus during the cell cycle depending on Ran and cyclin B

The proliferation marker pKi-67 ('Ki-67 antigen') is commonly used in clinical and research pathology to detect proliferating cells, as it is only expressed during cell-cycle progression. Despite the fact that this antigen has been known for nearly two decades, there is still no adequate understanding of its function. This study has therefore identified proteins that interact with pKi-67, using a yeast two-hybrid system. A mammalian two-hybrid system and immunoprecipitation studies were used to verify these interactions. Among other cell-cycle regulatory proteins, two binding partners associated with the small GTPase Ran were identified. In addition, DNA-structural and nucleolus-associated proteins binding to pKi-67 were found. Moreover, it was demonstrated that the N-terminal domain of pKi-67 is capable of self-binding to its own repeat region encoded by exon 13. Since RanBP, a protein involved in the transport of macromolecules over the nuclear lamina, was found to be a binding partner, a possible effect of pKi-67 on the localization of cell-cycle regulatory proteins was proposed. To test this hypothesis, a tetracycline-responsive gene expression system was used to induce the pKi-67 fragments previously used for the two-hybrid screens in HeLa cells. Subsequent immunostaining revealed the translocation of cyclin B1 from cytoplasm to nucleoli in response to this expression. It is suggested that pKi-67 is a Ran-associated protein with a role in the disintegration and reformation of the nucleolus and thereby in entry into and exit from the M-phase.

The proliferation marker pKi-67 becomes masked to MIB-1 staining after expression of its tandem repeats

The Ki-67 antigen, pKi-67, is one of the most commonly used markers of proliferating cells. The protein can only be detected in dividing cells (G(1)-, S-, G(2)-, and M-phase) but not in quiescent cells (G(0)). The standard antibody to detect pKi-67 is MIB-1, which detects the so-called 'Ki-67 motif' FKELF in 9 of the protein's 16 tandem repeats. To investigate the function of these repeats we expressed three of them in an inducible gene expression system in HeLa cells. Surprisingly, addition of a nuclear localization sequence led to a complete absence of signal in the nuclei of MIB-1-stained cells. At the same time antibodies directed against different epitopes of pKi-67 did not fail to detect the protein. We conclude that the overexpression of the 'Ki-67 motif', which is present in the repeats, can lead to inability of MIB-1 to detect its antigen as demonstrated in adenocarcinoma tissue samples. Thereafter, in order to prevent the underestimation of Ki-67 proliferation indices in MIB-1-labeled preparations, additional antibodies (for example, MIB-21) should be used. Additionally, we could show in a mammalian two-hybrid assay that recombinant pKi-67 repeats are capable of self-associating with endogenous pKi-67. Speculating that the tandem repeats are intimately involved in its protein-protein interactions, this offers new insights in how access to these repeats is regulated by pKi-67 itself.

Defects in G1-S cell cycle control in head and neck cancer: a review

Tumors gradually develop as a result of a multistep acquisition of genetic alterations and ultimately emerge as selfish, intruding and metastatic cells. The genetic defects associated with the process of tumor progression affect control of proliferation, programmed cell death, cell aging, angiogenesis, escape from immune control and metastasis. Fundamental cancer research over the last thirty years has revealed a multitude of genetic alterations which specify more or less separate steps in tumor development and which are collectively responsible for the process of tumor progression. The genes affected play in normal cells a crucial role in control over cell duplication and the interaction between cells, and between cells and their direct surrounding. This is illustrated on control during the G1/S phase of the cell cycle by its ultimate regulators: cyclins and cyclin dependent kinases. These proteins not only control the transition through the G1/S phase of the cell cycle, but also serve as mediators of the interaction between cells, and between cells and their surrounding. Defaults in the regulation of these proteins are associated with tumor progression, and, therefore, serve as targets for therapy. Defaults in those genes are found in various tumor types, although some of those prevail in particular tumor types. In this review emphasis is given to the defaults that occur in head and neck cancer.

Suppression of cell division by pKi-67 antisense-RNA and recombinant protein

The human antigen defined by the monoclonal antibody Ki-67 (pKi-67) is a human nuclear protein strongly associated with cell proliferation and found in all tissues studied. It is widely used as a marker of proliferating cells, yet its function is unknown. To investigate its function we suppressed pKi-67 expression by antisense RNA and overexpressed a partial structure of pKi-67 in HeLa cells. A BrdU-incorporation assay showed a significant decrease in DNA synthesis after antisense inhibition. Cell cycle analysis indicated a higher proportion of cells in G1 phase and a lower proportion of cells in S phase while the number of G(2)/M phase cells remained constant. Overexpression of a recombinant protein encoding three of the repetitive elements from exon 13 of pKi-67 had a similar effect to that obtained by antisense inhibition. The similarity of the effect of expressing 'Ki-67 repeats' and pKi-67 antisense RNA could be explained by a negative effect on the folding of the endogenous protein in the endoplasmatic reticulum. Furthermore excessive self-association of pKi-67 via the repeat structure could inhibit its nuclear transport, preventing it from getting to its presumptive site of action. We conclude that the Ki-67 protein has an important role in the regulation of the cell cycle, which is mediated in part by its repetitive elements.

Ki67 protein: the immaculate deception?

This article updates our previous review of Ki67 published in Histopathology 10 years ago. In this period the numbers of papers published featuring this antibody has increased 10-fold from 338 to 3489 indicating the considerable enthusiasm with which this antibody has been studied. This review attempts to provide an update on the characterization of the Ki67 protein, its function and its use as a prognostic or diagnostic tool.

Expression of cyclin-dependent kinase inhibitors, p21cip1 and p27kip1, during wound healing in rats

Wound healing is a physiological process in which growth of cells is stringently regulated. Cell growth is controlled by cell cycle-related proteins in which the cyclin kinase inhibitors cause cell cycle arrest and inhibit proliferation. However, little is known about the expression and the role of cyclin kinase inhibitors during wound healing in vivo. This study was mainly designed to examine the expression of p21cip1 and p27kip1 in excisional wounds of full-thickness skin in rats. Concomitant expression of proliferation marker Ki67 was also examined. Proliferation predominantly occurred in the first week after injury, peaking at postwounding day 5. Expression of both p21cip1 and p27kip1 at the gene and protein levels did occur during wound healing and showed an inverse gradient to that of Ki67. Constitutive p27kip1 was expressed throughout wound healing with low levels during the proliferating period of days 3 and 5 and increased levels during post-mitotic and remodeling stages. In contrast, p21cip1 was expressed transiently with detectable levels only between days 7 and 14 by Western blot analysis. Immunohistochemically, epithelial cells, endothelial cells and fibroblasts all could express both p21cip1 and p27kip1. In conclusion, the overall results suggested that p21cip1 and p27kip1 may play a key role in supervising the growth resulting from cell proliferation in tissue repair.

A risk-stratification model of non-small cell lung cancers using cyclin E, Ki-67, and ras p21: different roles of G1 cyclins in cell proliferation and prognosis

A large number of biological factors that seem to have important prognostic significance have been identified in non-small cell lung cancers (NSCLCs). In the present study, we have characterized expression of cyclin D1 and cyclin E in a cohort of 217 resected NSCLCs from a single institution by immunohistochemistry to analyze their expression in relation to the growth fraction determined by Ki-67 and to prognosis, and then we have constructed a risk-stratification model of cancer death by multiple biological factors in p-stage I NSCLCs. The cyclin E labeling index (LI) was significantly associated with the Ki-67 LI (r = 0.45; P < 0.001). Tumors having high-level cyclin E expression (cyclin E LI > or =30%) showed a significantly higher Ki-67 LI than tumors having low-level cyclin E expression (cyclin E LI <30%; P < 0.001), whereas positive or negative cyclin D1 expression was not associated with the Ki-67 LI (P = 0.1). Cyclin E expression was a significant and independent unfavorable prognostic factor (hazards ratio = 2.09; P = 0.03), as reported previously (Clin. Cancer Res., 6: 11-16, 2000), whereas cyclin D1 expression was not. These findings indicate different roles of cyclin D1 and cyclin E in cell proliferation and in the prognosis of NSCLCs. Furthermore, we stratified this cohort of p-stage I NSCLCs into different survival groups by using biological factors, including cyclin E, Ki-67, and ras p21, which previously we have found to be independent prognostic factors among 10 factors studied in p-stage I NSCLCs. Four groups of patients with markedly different survivals were identified with 5-year survival rates that ranged from 96% for patients with no factors altered to 41% for patients with all three factors altered (P < 0.001). This combination of biological factors was a significant and independent prognostic factor (hazards ratio = 7.94; P = 0.001).

Reduced proliferation and cell adhesion in endometriosis

Endometriosis is defined as endometriotic tissues growing outside the uterine cavity. The cell biological processes responsible for the pathogenesis of this disease are not well understood. In order to detect differences in proliferative activity between endometria and endometriotic lesions, Ki67 staining was analysed. In addition, expression of epidermal growth factor (EGF) and its receptor was examined using immunohistochemistry. For dedifferentiation processes pointing to invasive properties of the uterine epithelium, the presence of the adhesion complex E-cadherin with the associated alpha- and beta-catenin was investigated. Specimens of endometrium in the proliferative phase of 36 patients without, and 79 patients with, endometriosis together with endometriotic lesions were studied. The study revealed a significantly reduced proliferation activity in uterine epithelium within the ectopic lesions but no differences between eutopic endometria of non-affected and affected patients. Furthermore, a lower expression of both EGF and its receptor in the epithelial cells of the ectopic glands was observed. The adhesion complex E-cadherin, together with alpha-, and beta-catenin, was slightly reduced in uterine epithelial cells of women with endometriosis and less expressed in endometriotic lesions. The results indicate that epithelial cells of endometriotic lesions are not hyperproliferative, but do appear to dedifferentiate, displaying an invasive character.

Correlation of increased apoptosis and proliferation with development of prostatic intraepithelial neoplasia (PIN) in ventral prostate of the Noble rat

BACKGROUND

Imbalance between cell proliferation and cell apoptosis has been considered a key factor in carcinogenesis. Prostatic intraepithelial neoplasia (PIN) is the most likely precancereous lesion and represents the major target for chemoprevention of prostate cancer. The proliferative and apoptotic activities involved in the development of PIN remain to be elucidated.

METHODS

Ventral prostates were removed from Noble rats that were treated with a combination of testosterone (T) and estradiol (E(2)) for certain periods of time, and processed for histopathological grading. To evaluate the relationship between cell proliferation and apoptosis, immunohistochemistry for proliferating cell nuclear antigen (PCNA), Ki-67, and in situ DNA nick labeling (TUNEL) for identifying apoptotic cells, were performed on paraffin sections from prostate samples with PIN lesions. The results were correlated with expression patterns of Bcl-2 and Bax, two proteins related to cell survival and cell apoptosis.

RESULTS

Pathologically, low-grade PIN (LGPIN) and high-grade PIN (HGPIN) were observed in ducts or alveoli after 3 and 5 months of T + E(2) treatment, respectively. Quantitative evaluation of Ki-67 showed an increased proliferative activity in HGPIN. In contrast to normal prostatic ducts and alveoli, which showed no positive staining for Ki-67 in the nuclei of luminal cells, 25% Ki-67-positive cells were detected in luminal cells of HGPIN. Only 7.5% Ki-67-positive cells were found belonging to the basal cell type. The Ki-67 index showed a higher growth rate from normal to HGPIN. The PCNA results showed a similar expression pattern to that of Ki-67 in normal prostate, LGPIN, and HGPIN. Apoptotic index (number of apoptotic cells/total number of cell counted) was significantly higher (P = 0.028) in HGPIN (3.23%) than in control prostate (1.19%). In contrast to control prostate, which showed no definite expression of Bcl-2, an intense positive expression of Bcl-2 in HGPIN was observed. Positive expression of Bax protein was observed in glandular epithelial cells of normal control prostate and HGPIN as well.

CONCLUSIONS

Overexpression of Bcl-2 and higher Ki-67 or PCNA indices in HGPIN suggest that abnormal growth of premalignant lesions might result from an increase in cell proliferation. An increased apoptotic rate in HGPIN further implicates that active apoptosis may accelerate cell turnover in the development of premalignant lesions of the prostate.

The Ki-67 protein: fascinating forms and an unknown function

The Ki-67 protein is a nuclear and nucleolar protein, which is tightly associated with somatic cell proliferation. Antibodies raised against the human Ki-67 protein paved the way for the immunohistological assessment of cell proliferation, particularly useful in numerous studies on the prognostic value of cell growth in clinical samples of human neoplasms. The primary structure revealed potential phosphorylation site for a range of essential kinases, PEST sequences, and a forkhead-associated domain, which are features present in a variety of cell-cycle-regulating proteins, but information about the position of the Ki-67 protein within the protein network that drives the cell cycle remained scarce. There is now evidence that posttranslational modifications based on phosphorylation by cdc2 kinase and PKC accompany the remarkable redistribution of the Ki-67 protein from the interior of the nucleus to the perichromosomal layer during mitosis and vice versa. The discovery of Ki-67 equivalents in other species is advantageous for a precise and cross-species investigation of the structural requirements for its yet unknown function. The recently published data add new pieces to the challenging puzzle of this multifaceted protein, which are waiting to be put together.

The temporal and spatial distribution of p21WAF expression in skin appendages

p21WAF is a cyclin-dependent kinase inhibitor which is widely expressed in epidermal structures. Using a combination of double immunocytochemical staining and combined in situ hybridization, we show that there is a striking exclusivity between the expression of Ki67 and p21WAF in the hair matrix. Some cells that are Ki67-positive also express p53, but as they exit the cell cycle they assume p21WAF-positive/p53-negative status. By contrast, cells in the interfollicular epidermis of psoriatic lesions, in the sebaceous gland, and in the outer root sheath are p21WAF-positive/p53-positive but Ki67-negative. These results suggest that in some anatomical parts of the epidermis, p21WAF expression can accompany p53 expression, whereas in other parts, the expression of these markers is reciprocal, suggesting that other pathways may be controlling p21WAF expression. In order to define, functionally, the presence of p53-independent p21WAF expression in skin, we examined lesions of Bowen's disease in which both alleles of p53 were inactivated. p21WAF expression was still observed, confirming a role for p53-independent expression of p21WAF in human skin in vivo.

The location of pKi67 in the outer dense fibrillary compartment of the nucleolus points to a role in ribosome biogenesis during the cell division cycle

Although widely used as a marker of cell proliferation, the biochemical properties and function of the Ki67 antigen remain poorly understood. Recent data indicate that it can interact with RNA, DNA, and a number of cellular proteins including elements of the ubiquitin proteolytic pathway and a novel kinase. The evidence for its expression only in cycling cells is extensive and it is not regulated by stress, apoptosis or DNA damage. It was reasoned that a detailed characterization of the localization of pKi67 and analysis of its spatial relationship to other nucleolar proteins may provide insights into its function. Using high-resolution laser scanning confocal microscopy with double and triple labelling, pKi67 expression in MCF7 cells has been defined in relation to the distribution of nucleolin, fibrillarin, p130 (human Nopp 140 homologue), p120 (Nol 1), RH-II/Gu helicase, and topoisomerase II beta. All of these molecules are perichromosomal during mitosis and all but fibrillarin and p130 show extra-nucleolar distribution in early G1. The majority of p120 (Nol 1) and RH-II/Gu helicase co-localize in the diffuse fibrillar centre (DFC) of nucleoli, while there is only partial overlap with nucleolin and fibrillarin. There is no co-localization between p130 and pKi67. These data refine current understanding of the distribution of pKi67 and its physical relationship with functional domains of the nucleolus and place pKi67 in a zone of the DFC associated with late rRNA processing. Taken together with recent biochemical data, these observations allow the proposal of a model of pKi67 function in which it acts as an 'efficiency factor' in ribosome biogenesis during the heavy metabolic demands placed on a cell during the cell division cycle.

The Ki-67 protein: from the known and the unknown

The expression of the human Ki-67 protein is strictly associated with cell proliferation. During interphase, the antigen can be exclusively detected within the nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. The fact that the Ki-67 protein is present during all active phases of the cell cycle (G(1), S, G(2), and mitosis), but is absent from resting cells (G(0)), makes it an excellent marker for determining the so-called growth fraction of a given cell population. In the first part of this study, the term proliferation marker is discussed and examples of the applications of anti-Ki-67 protein antibodies in diagnostics of human tumors are given. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of the disease. The best-studied examples in this context are carcinomas of the prostate and the breast. For these types of tumors, the prognostic value for survival and tumor recurrence has repeatedly been proven in uni- and multivariate analysis. The preparation of new monoclonal antibodies that react with the Ki-67 equivalent protein from rodents now extends the use of the Ki-67 protein as a proliferation marker to laboratory animals that are routinely used in basic research. The second part of this review focuses on the biology of the Ki-67 protein. Our current knowledge of the Ki-67 gene and protein structure, mRNA splicing, expression, and cellular localization during the cell-division cycle is summarized and discussed. Although the Ki-67 protein is well characterized on the molecular level and extensively used as a proliferation marker, the functional significance still remains unclear. There are indications, however, that Ki-67 protein expression is an absolute requirement for progression through the cell-division cycle.

The role of p53, MDM2 and c-erb B-2 oncoproteins, epidermal growth factor receptor and proliferation markers in the prognosis of urinary bladder cancer

The immunohistological expression of p53 and MDM2 oncoproteins was examined in paraffin embedded tissue from 106 patients with transitional cell carcinoma of the urinary bladder and was related to various clinicopathological features, the expression of proliferation associated markers (proliferating cell nuclear antigen - PCNA - and Ki-67), c-erb B-2 oncoprotein and epidermal growth factor receptor (EGFR), as well as to survival. MDM2 immunoreactivity was seen in 38% of our cases, and in 14% was accompanied by p53 positive immunohistochemistry. The rate of p53 positivity was associated with grade, stage and papillary status, whereas MDM2 immunopositivity increased with grade and stage (Ta VS T1), and MDM2 labeling index (LI) with stage. MDM2 expression was related to p53 expression and less strongly to proliferation rate (Ki-67 LI). The simultaneous p53 and MDM2 expression was more frequently observed in higher grade and stage tumours. C-erb B-2, EGFR and proliferation marker expression increased with grade, stage and non-papillary configuration. In univariate analysis high grade, solid growth pattern, advanced T-category, cystectomy, EGFR and Ki-67 expression were linked to shorter overall survival but only Ki-67 LI, along with T-category and type of therapy, had independent prognostic value. C-erb B-2 expression and stage were the two independent predictors of disease-free survival and Ki-67 LI and EGFR LI the independent predictors of post-relapse survival. For patients with superficial tumors PCNA LI emerged as the single independent determinator of survival. p53 and MDM2 expression did not appear to have any significant impact on survival, although the simultaneous expression of p53 and MDM2 turned out to be a highly significant parameter of shortened overall survival in univariate analysis.