p27Kip1 is expressed in proliferating cells in its form phosphorylated on threonine 187.
BACKGROUND: G1/S cell cycle progression requires p27Kip1 (p27) proteolysis, which is triggered by its phosphorylation on threonine (Thr) 187. Since its levels are abundant in quiescent and scarce in cycling cells, p27 is an approved marker for quiescent cells, extensively used in histopathology and cancer research. METHODS: However here we showed that by using a specific phosphorylation site (pThr187) antibody, p27 is detectable also in proliferative compartments of normal, dysplastic and neoplastic tissues. RESULTS: In fact, whereas un-phosphorylated p27 and MIB-1 showed a significant inverse correlation (Spearman R = -0.55; p < 0,001), pThr187-p27 was positively and significantly correlated with MIB-1 expression (Spearman R = 0.88; p < 0,001). Thus proliferating cells only stain for pThr187-p27, whereas they are un-reactive with the regular p27 antibodies. However increasing the sensitivity of the immunocytochemistry (ICH) by the use of an ultra sensitive detection system based on tiramide signal amplification, simultaneous expression and colocalisation of both forms of p27 was shown in proliferating compartments nuclei by double immunofluorescence and laser scanning confocal microscopy studies. CONCLUSION: Overall, our data suggest that p27 expression also occurs in proliferating cells compartments and the combined use of both regular and phospho- p27 antibodies is suggested.
Troncone
Giancarlo
G
Dipartimento di Scienze Biomorfologiche e Funzionali, Facoltà di Medicina e Chirurgia, Università Federico II, Napoli, Italy. giancarlo.troncone@unina.it.
Martinez
Juan C
JC
Iaccarino
Antonino
A
Zeppa
Pio
P
Caleo
Alessia
A
Russo
Maria
M
Migliaccio
Ilenia
I
Motti
Maria L
ML
Califano
Daniela
D
Palmieri
Emiliano A
EA
Palombini
Lucio
L
EMBO J. 1997 Sep 1;16(17):5334-44
9311993
Blood. 1999 Jul 15;94(2):765-72
10397744
J Pathol. 1992 Dec;168(4):357-63
1484317
Am J Pathol. 1997 Jul;151(1):151-60
9212741
Nat Med. 1997 Feb;3(2):231-4
9018245
Am J Pathol. 2002 Feb;160(2):511-9
11839571
Genes Dev. 1999 May 1;13(9):1181-9
10323868
Am J Pathol. 1998 Feb;152(2):585-90
9466585
Nat Med. 1997 Feb;3(2):222-5
9018243
Mod Pathol. 2001 Oct;14(10):1036-42
11598175
Cancer. 2003 Feb 1;97(3):644-8
12548606
J Clin Endocrinol Metab. 2002 Jun;87(6):2635-43
12050228
Brain Pathol. 2002 Oct;12 (4):412-9
12408227
Cell. 1994 Jul 15;78(1):59-66
8033212
Am J Surg Pathol. 1999 Jun;23(6):678-85
10366150
Mod Pathol. 1999 Aug;12(8):751-5
10463475
Am J Pathol. 1998 Aug;153(2):505-13
9708810
J Clin Pathol. 1999 Dec;52(12):880-7
10711250
Nat Med. 1997 Feb;3(2):152-4
9018230
Am J Pathol. 1999 Feb;154(2):313-23
10027389
Am J Pathol. 2003 Nov;163(5):1687-98
14578166
Aging Cell. 2003 Apr;2(2):105-10
12882323