Nucleoplasmic LAP2 alpha-lamin A complexes are required to maintain a proliferative state in human fibroblasts

In human diploid fibroblasts (HDFs), expression of lamina-associated polypeptide 2 (LAP2) upon entry and exit from G0 is tightly correlated with phosphorylation and subnuclear localization of retinoblastoma protein (Rb). Phosphoisoforms of Rb and LAP2 are down-regulated in G0. Although RbS780 phosphoform and LAP2 are up-regulated upon reentry into G1 and colocalize in the nucleoplasm, RbS795 migrates between nucleoplasmic and speckle compartments. In HDFs, which are null for lamins A/C, LAP2 is mislocalized within nuclear aggregates, and this is correlated with cell cycle arrest and accumulation of Rb within speckles. Nuclear retention of nucleoplasmic Rb during G1 phase but not of speckle-associated Rb depends on lamin A/C. siRNA knock down of LAP2 or lamin A/C in HDFs leads to accumulation of Rb in speckles and G1 arrest, probably because of activation of a cell cycle checkpoint. Our results suggest that LAP2 and lamin A/C are involved in controlling Rb localization and phosphorylation, and a lack or mislocalization of either protein leads to cell cycle arrest in HDFs

The Two Faces of Cervical Adenocarcinoma In Situ

In order of frequency, cervical intraepithelial neoplasia (CIN), combined adenocarcinoma in situ (AIS)/CIN lesions, and solitary AIS are the most prevalent premalignant lesions of the uterine cervix. As the morphologic distinction of these subtypes is not always straightforward, we performed an immunophenotyping analysis to establish distinguishing profiles for each of these squamous and glandular progenitor lesions of cervical carcinoma. A series of 26 premalignant cervical lesions, comprising 13 cases of AIS, of which 7 represented solitary AIS and 6 were combined with CIN (combined AIS/CIN), as well as 13 solitary high-grade CIN lesions, were immunophenotypically analyzed using antibodies directed against p16, p63, bcl-2, and cytokeratins (CK) 5, 7, 8, 13, 17, 18, and 19. Adjacent normal epithelia were also investigated. CIN lesions expressed the full panel of antibodies. Combined AIS/CIN lesions also expressed the full complement of markers in both the AIS and CIN compartments. However, the expression of p63, bcl-2, CK5, and CK17 was lower in AIS compared with CIN. The solitary AIS lesions could be subdivided into 2 subgroups, 1 expressing the full complement of markers and a second group in which no expression of p63, bcl-2, CK5, and a sporadically CK17 expression was observed. We conclude that 2 phenotypically distinct types of AIS can be identified, that is, AIS with a reserve cell marker phenotype and AIS with an endocervical glandular phenotype. These observations support the view that reserve cells are capable of bidirectional premalignant transformation, that is, into CIN and reserve cell-type AIS, as well as combined AIS/CIN. The endocervical type of AIS is probably a result of the unidirectional transformation of progenitor cells within the glandular cell compartment