Nephrol Dial Transplant (2003) 18: III9-III12
© 2003 European Renal Association-European Dialysis and Transplant Association
Original Article
Parathyroid cell growth in patients with advanced secondary hyperparathyroidism: vitamin D receptor and cyclin-dependent kinase inhibitors, p21 and p27
Masanori Tokumoto,
Kazuhiko Tsuruya,
Kyoichi Fukuda,
Hidetoshi Kanai,
Shoji Kuroki1,
Hideki Hirakata and
Mitsuo Iida
Departments of Medicine and Clinical Science, and
1 Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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Abstract
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Uraemic patients with advanced secondary hyperparathyroidism
(2HPT) have nodular hyperplastic glands with a decreased vitamin
D receptor (VDR) density. Previous studies have shown that nodular
hyperplasia expressed a significantly lower VDR density as compared
with diffuse hyperplasia, and the VDR density negatively correlated
with both the glandular weight and the marker of cell proliferation.
However, the mechanism by which the decreased VDR density leads
to parathyroid cell proliferation remains unclear. In the myelomonocytic
cell line, active vitamin D
3 is known to activate the transcription
of both p21 and p27, cyclin-dependent kinase inhibitors (CDKIs),
regulating the transition from the G
1 to the S phase of the
cell cycle, in a VDR-dependent manner. Moreover, the overexpression
of p21 and p27 inhibits cell proliferation. In order to elucidate
the mechanism of parathyroid cell proliferation, the expression
of CDKIs, p21 and p27, and the VDR was analysed immunohistochemically,
and compared among nodular and diffuse hyperplastic parathyroid
glands, and histologically normal parathyroid glands. The VDR
expression in nodular hyperplasias was significantly decreased
compared with either diffuse hyperplasias or normal parathyroid
glands. The expression of both p21 and p27 was also significantly
lower in nodular hyperplasias than in diffuse hyperplasias or
normal parathyroid glands. Sections of parathyroid glands with
a high expression of nuclear VDR highly expressed both p21 and
p27. In nodular hyperplasias, the expression of both p21 and
p27 correlated either positively with the nuclear VDR expression
or inversely with the glandular weight. Therefore, the reduced
expression of p21 and p27, being VDR dependent, is a major pathogenic
factor for nodular parathyroid gland growth in advanced 2HPT.
Keywords: cyclin-dependent kinase inhibitor; haemodialysis; p21; p27; secondary hyperparathyroidism; vitamin D receptor
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Introduction
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A number of pathogenic factors, including hypocalcaemia, phosphate
retention, vitamin D deficiency, reduced density of both vitamin
D receptors (VDRs) and Ca
2+-sensing receptors (CaRs) in the
parathyroid cells, contribute to the development of secondary
hyperparathyroidism (2HPT) in patients with chronic renal failure
[
1–
3]. The characteristic findings of renal hyperparathyroidism
are the asymmetrical enlargement as well as the nodularity of
the parathyroid glands, and an increase in both oxyphilic and
transitional oxyphilic cells. In spite of the identical environmental
factors, such as the serum concentrations of calcium, phosphorus
and active vitamin D
3 (1,25D), the growth of the parathyroid
glands varies in the same patient, suggesting that the respective
parathyroid glands have asymmetrical abnormalities for sensing
environmental factors.
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Resistance to the physiological concentration of serum 1,25D in nodular hyperplasia
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The inhibitory effects of 1,25D on 2HPT have been shown during
either oral or intravenous 1,25D pulse therapy [
4–
6],
which decreases the concentration of serum parathyroid hormone
(PTH). In patients with severe 2HPT, the hyperplastic parathyroid
glands often show resistance to the physiological concentration
of serum 1,25D [
5,
7–
9], and this can be partly explained
by VDR deficiency in hyperplastic glands [
10–
12].
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Receptor abnormalities and cell proliferation in the hyperplastic parathyroid glands
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Parathyroid hyperplasia in patients with chronic renal failure
has been classified into two major patterns, diffuse and nodular,
and the weight of nodular hyperplasia is usually heavier. It
has been postulated that the pattern of hyperplasia may change
from diffuse to nodular as the parathyroid gland becomes heavier
[
13,
14]. Fukuda
et al. reported that nodular hyperplasia had
a significantly lower VDR density than diffuse hyperplasia,
and that the VDR density negatively correlated with both the
weight and proliferative activity of the hyperplastic parathyroid
glands in patients with advanced 2HPT [
2].
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Antiproliferative effect of 1,25D
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The antiproliferative effect of 1,25D on the parathyroid glands
has also been demonstrated in 2HPT patients undergoing oral
1,25D pulse therapy, leading to a decrease in the size of the
hyperplastic glands [
4]. Kremer
et al. showed that 1,25D abolished
the expression of a proto-oncogene, c-
myc, and delayed the subsequent
proliferation of bovine parathyroid cells in primary culture
[
15]. However, nodular hyperplastic glands, expressing a lower
VDR density, are often resistant to 1,25D pulse therapy as compared
with diffuse hyperplasia [
2].
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Regulation of parathyroid cell growth by 1,25D via the VDR
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Parathyroid cell proliferation is reduced by 1,25D, which decreases
the expression of the proto-oncogene, c-
myc [
15]. This gene
modulates the progression from the G
1 to the S phase of the
cell cycle. A decrease in the plasma concentration of 1,25D
and/or a disturbance of its action at the level of the parathyroid
cell, which are both observed frequently in uraemic patients,
can decrease the inhibition of c-
myc expression and lead to
progression of the cell cycle. Futhermore, Liu
et al. found
that p21, a cyclin-dependent kinase inhibitor (CDKI), is transcriptionally
induced by 1,25D in a VDR-dependent manner, but not in a p53-dependent
manner, and p27 is also induced by 1,25D in the myelomonocytic
cell line, U937 [
16]. It is known that the p21 and p27 genes
coding CDKI regulate progression from the G
1 to the S phase
of the cell cycle by inhibiting cyclin-dependent kinase [
17–
19].
Moreover, Cozzolino
et al. recently demonstrated that in uraemic
rats, the efficacy of 1,25D, and its less calcaemic analogue
19-nor-1,25D, in preventing high phosphorus-induced parathyroid
hyperplasia could be partially explained by the induction of
parathyroid p21 expression. They also reported that the increases
in p21 correlated inversely with reduced Ki67 [
20]. Their findings
indicate another possible mechanism by which calcitriol may
regulate the proliferation of parathyroid cells.
We have therefore hypothesized that the reduced p21 and p27 production via decreased nuclear VDR expression leads to parathyroid cell proliferation, particularly in nodular hyperplasia.
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Relationship between the VDR and CDKI, p21 and p27
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Immunohistochemical staining of VDR protein revealed mainly
nuclear localization and, to a lesser degree, cytoplasmic localization
of each histological type. In our study, nodular hyperplasias
showed a significantly lower VDR density than diffuse hyperplasias
or normal parathyroid glands, being compatible with previous
reports [
2]. Therefore, the effects of 1,25D through the VDR
might be limited in nodular hyperplasia. Expression of both
p21 and p27 proteins revealed nuclear localization, and the
semi-quantitative analyses showed that the expression of both
p21 and p27 in nodular hyperplasias was also significantly lower
than in diffuse hyperplasias or normal parathyroid glands, as
in the case of the VDR. Using serial sections, the distribution
of the VDR and either p21 or p27 was examined. It was revealed
that the sections of parathyroid glands with high nuclear VDR
expression elicited high p21 and p27 expression, whereas the
sections that lacked the VDR had no detectable p21 or p27. Moreover,
a significant positive correlation between VDR expression and
the expression of either p21 or p27 was found only in nodular
hyperplasia [
21]. Our results suggest that p21 and p27 expression
may be regulated in a VDR-dependent manner in hyperplastic parathyroid
glands (Figure 1
), as observed in the myelomonocytic cell line,
U937 [
16]. Indeed, a functional vitamin D response has been
identified in the p21 promoter area [
16], but not in the p27
promoter area.
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Fig. 1. Impact of vitamin D receptor (VDR) and cell cycle dependent-kinase inhibitors, p21 and p27, on parathyroid cell proliferation in patients with advanced secondary hyperparathyroidism (2HPT). The reduction of both p21 and p27 expression, being VDR dependent, is a major pathogenic factor for nodular parathyroid gland growth in advanced 2HPT due to uraemia.
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Relationship between CDKI, p21 and p27, and parathyroid cell growth
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Both p21 and p27 proteins participate in regulating the transition
from the G
1 to the S phase of the cell cycle [
17,
18]. Dusso
et al. [
22] elegantly demonstrated the direct effect of phosphorus
on parathyroid cell proliferation in the early phase of uraemia
in 5/6 nephrectomized rats. Low dietary phosphorus induced p21
expression, whereas high phosphorus intake enhanced transforming
growth factor-
(TGF-
) with a subsequent stimulation of parathyroid
cell proliferation independent of the changes in concentration
of serum 1,25D. In their study, there was a significant correlation
between decreased p21 expression and enhanced proliferating
cell nuclear antigen (PCNA) expression, showing a direct relationship
between p21 and parathyroid cell proliferation. In our study,
the weight of the resected glands inversely correlated with
the expression of either p21 or p27 in nodular hyperplasias.
Semi-quantitatively, the expression of Ki67 antigen was significantly
higher in nodular hyperplasias than in both diffuse hyperplasias
and normal parathyroid glands. The expression of Ki67 antigen
did not correlate with the expression of both p21 and p27 in
our study, although the expression of Ki67 antigen was significantly
higher in nodular hyperplasia [
21]. Therefore, our results also
support the hypothesis that decreased expression of both p21
and p27 can lead to parathyroid cell proliferation in advanced
2HPT (Figure 1
). Thus, the transcriptional up-regulation of
both p21 and p27 genes due to 1,25D may be one of the mechanisms
of the antiproliferative effects of the 1,25D–VDR complex
which block G
1–S transition.
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Possible management of 2HPT by modulating CDKI, p21 and p27
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The decreased VDR expression and the deficiency of 1,25D play
a major role in parathyroid cell proliferation and continuous
oversecretion of PTH, even after correction of the calcium–phosphorus
imbalance. For the prevention and management of 2HPT, it is
thus crucial to understand the mechanisms regulating the VDR-dependent
inhibition of cell growth. Induction of p21 arrests growth in
monocyte–macrophages [
16], keratinocytes [
23] and human
cancer cells [
24], as well as suppressing tumorigenicity
in vivo [
25]. Induction of p27 also induces growth arrest in monocyte–macrophages
[
16].
In situ immunohistochemical analyses of p21 and p27 expression in tissue samples of hyperplastic parathyroid glands, obtained by a needle biopsy, may be a useful technique for estimating both the responsiveness to 1,25D therapy and an indication for parathyroidectomy. Up-regulation of the VDR content by 1,25D administration could correct the parathyroid VDR density, and therefore normalize p21 and p27 levels.
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Conclusion
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The higher mitogenic properties observed in nodular hyperplasia
of the parathyroid glands in patients with advanced 2HPT can
be attributed to the reduced expression of the CDKIs, p21 and
p27, being associated with the down-regulated VDR expression
in parathyroid cells. Based on the present results and other
published reports, we conclude that the decreased VDR-dependent
expression of both p21 and p27 is a major cause of the advanced
parathyroid cell growth in 2HPT.
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Acknowledgments
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Part of this paper has been published in
Kidney International,
62(4), pp. 1196–1207 and has been reproduced with the
permission of the publisher.
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Notes
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Correspondence and offprint requests to: Masanori Tokumoto,
Department of Medicine and Clinical Science, Graduate School
of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-Ku,
Fukuoka, 812-8582, Japan. Email:
tokumoto{at}intmed2.med.kyushu-u.ac.jp 
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References
|
|---|
- Llach F. Secondary hyperparathyroidism in renal failure: the trade-off hypothesis revisited. Am J Kidney Dis 1995; 25:663–679[Web of Science][Medline]
- Fukuda N, Tanaka H, Tominaga Y et al. Decreased 1,25-dihydroxyvitamin D3 receptor density is associated with a more severe form of parathyroid hyperplasia in chronic uremic patients. J Clin Invest 1993; 92:1436–1443
- Kifor O, Moore FJ, Wang P et al. Reduced immunostaining for the extracellular Ca2+-sensing receptor in primary and uremic secondary hyperparathyroidism. J Clin Endocrinol Metab 1996; 81:1598–1606[Abstract]
- Fukagawa M, Okazaki R, Takano K et al. Regression of parathyroid hyperplasia by calcitriol-pulse therapy in patients on long-term dialysis. N Engl J Med 1990; 323:421–422[Web of Science][Medline]
- Slatopolsky E, Weerts C, Thielan J et al. Marked suppression of secondary hyperparathyroidism by intravenous administration of 1,25-dihydroxy-cholecalciferol in uremic patients. J Clin Invest 1984; 74:2136–2143
- Cannella G, Bonucci E, Rolla D et al. Evidence of healing of secondary hyperparathyroidism in chronically hemodialysed uremic patients treated with long-term intravenous calcitriol. Kidney Int 1994; 46:1124–1132[CrossRef][Web of Science][Medline]
- Chan YL, McKay C, Dye E et al. The effect of 1,25 dihydroxycholecalciferol on parathyroid hormone secretion by monolayer cultures of bovine parathyroid cells. Calcified Tissue Int 1986; 38:27–32[Web of Science][Medline]
- Delmez JA, Tindira C, Grooms P et al. Parathyroid hormone suppression by intravenous 1,25-dihydroxyvitamin D: a role for increased sensitivity to calcium. J Clin Invest 1989; 83:1349–1355
- Dunlay R, Rodriguez M, Felsenfeld AJ et al. Direct inhibitory effect of calcitriol on parathyroid function (sigmoidal curve) in dialysis. Kidney Int 1989; 36:1093–1099[Web of Science][Medline]
- Korkor AB. Reduced binding of [3H]1,25-dihydroxyvitamin D3 in the parathyroid glands of patients with renal failure. N Engl J Med 1987; 316:1573–1577[Abstract]
- Merke J, Hugel U, Zlotkowski A et al. Diminished parathyroid 1,25 (OH)2D3 receptors in experimental uremia. Kidney Int 1987; 32:350–353[Medline]
- Brown AJ, Dusso A, Lopez HS et al. 1,25-(OH)2D receptors are decreased in parathyroid glands from chronically uremic dogs. Kidney Int 1989; 35:19–23[Medline]
- Tominaga Y, Sato K, Tanaka Y et al. Histopathology and pathophysiology of secondary hyperparathyroidism due to chronic renal failure. Clin Nephrol 1995; 144 [Suppl]:S42–S47
- Tominaga Y, Tanaka Y, Sato K et al. Histopathology, pathophysiology, and indications for surgical treatment of renal hyperparathyroidism. Semin Surg Oncol 1997; 13:78–86[CrossRef][Web of Science][Medline]
- Kremer R, Bolivar I, Goltzman D et al. Influence of calcium and 1,25-dihydroxycholecalciferol on proliferation and proto-oncogene expression in primary cultures of bovine parathyroid cells. Endocrinology 1989; 125:935–941[Abstract/Free Full Text]
- Liu M, Lee MH, Cohen M et al. Transcriptional activation of the Cdk inhibitor p21 by vitamin D3 leads to the induced differentiation of the myelomonocytic cell line U937. Genes Dev 1996; 10:142–153[Abstract/Free Full Text]
- Reed SI, Bailly E, Dulic V et al. G1 control in mammalian cells. J Cell Sci Suppl 1994; 18:69–73[Medline]
- Sherr CJ, Roberts JM. Inhibitors of mammalian G1 cyclin-dependent kinases. Gene Dev 1995; 9:1149–1163[Free Full Text]
- Niculescu AB 3rd, Chen X, Smeets M et al. Effects of p21 (Cip1/Waf1) at both the G1 and the G2/M cell cycle transitions: pRb is a critical determinant in blocking DNA replication and in preventing endoreduplication. Mol Cell Biol 1998; 18:629–643[Abstract/Free Full Text]
- Cozzolino M, Lu Y, Finch J et al. p21WAF1 and TGF- mediate parathyroid growth arrest by vitamin D and high calcium. Kidney Int 2001; 60:2109–2117[CrossRef][Web of Science][Medline]
- Tokumoto M, Tsuruya K, Fukuda K et al. Reduced p21, 27 and vitamin D receptor in the nodular hyperplasia in patients with advanced secondary hyperparathyroidism. Kidney Int 2002; 62:1196–1207[CrossRef][Web of Science][Medline]
- Dusso AS, Pavlopoulos TP, Naumovich L et al. p21WAF1 and transforming growth factor- mediate dietary phosphate regulation of parathyroid cell growth. Kidney Int 2001; 59:855–865[CrossRef][Web of Science][Medline]
- DiCunto F, Topley G, Calautti E et al. Inhibitory function of p21Cip1/WAF1 in differentiation of primary mouse keratinocytes independent of cell cycle control. Science 1998; 280:1069–1072[Abstract/Free Full Text]
- Bonfanti M, Taverna S, Salmona M et al. p21WAF–1-derived peptides linked to an internalization peptide inhibit human cancer cell growth. Cancer Res 1997; 57:1442–1446[Abstract/Free Full Text]
- Yang ZY, Perkins ND, Ohno T et al. The p21 cyclin-dependent kinase inhibitor suppresses tumorigenicy in vivo. Nat Med 1995; 1:1052–1056[CrossRef][Web of Science][Medline]
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Abstract
Introduction