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Summary The pNR-2/pS2 protein is regulated by oestrogens in breast cancer cell lines. This report describes a systematic survey of pNR-2/pS2 expression in a number of common epithelial tumours. Expression was evaluated immunohistochemically in an archival series using antisera raised against the C-terminus of the pNR-2/pS2 protein. Expression of pNR-2/pS2 by malignant epithelial tumours was widespread. Intense immunohistochemical staining was found in tumour cells in a proportion of pancreatic (6/8), large intestinal (7/12), gastric (9/16) and endometrial (4/12) carcinomas. Positive staining for the pNR-2/pS2 protein was also found in both benign and malignant ovarian epithelial tumours and was very significantly associated with mucinous differentiation (P <0.00001). Small numbers of carcinomas of bladder (2/10) and prostate (2/7) showed less intense staining and single examples of cervical carcinoma (1/7) and lung carcinoma (1/19) stained positively. None of the renal carcinomas (0/16) examined stained positively. Positive staining showed no correlation with gender. Although there are reports of oestrogen receptor expression in most of the tumour types considered, the possibility of other regulatory influences must also be considered. The pNR-2/pS2 protein may well have a more general role in human epithelial neoplasia than hitherto realised.

Summary The majority of Myeloproliferative Neoplasms (MPNs) are characterised by mutations in genes encoding molecules or receptors involved in cell signalling, the most common being the JAK2 V617F mutation. This mutation leads to ligand‐independent activation of downstream signalling pathways by constitutive phosphorylation. The signalling pathways affected include the Janus kinase‐signal transducers and activators of transcription (JAK‐STAT) and phosphotidylinositide‐3 kinase (PI3K) pathways, which regulate cell survival and apoptosis respectively. Monoclonal antibodies to phospho‐STAT5 and phospho‐Akt were generated and assessed by immunocytochemistry on bone marrow biopsies of MPN patients with JAK2 V617F, JAK2 exon 12, MPL exon 10 and KIT D816V mutations. JAK2 V617F mutation was associated with significantly increased levels of phosphorylated STAT5 and Akt in haemopoietic cells, most marked in megakaryocytes. In contrast, JAK2 exon 12 and MPL exon 10 mutations did not affect the level of phosphorylation. In systemic mastocytosis with KIT D618V mutation there was significantly increased expression of phosphorylated STAT5 and Akt in neoplastic mast cells although there was no change in the expression in other haemopoietic cells. JAK2 V617F is associated with upregulated phosphorylation of STAT5 and Akt in megakaryocytes, and to a lesser extent in other haemopoietic cells. Immunocytochemistry of bone marrow trephines for these phospho‐proteins can be used as a supplementary diagnostic test with a high negative predictive value.

Five peptides, corresponding to regions of the predicted protein sequence of the oestrogen-regulated pNR-2 protein which is expressed in oestrogen-responsive human breast cancer cells, were synthesized. Two peptides were immunogenic in rabbits and antisera against one peptide reacted with the pNR-2 protein in sections of formalin-fixed, paraffin-embedded breast tumour. There was a significant correlation between the extent of pNR-2 protein expression detected by immunohistochemistry and pNR-2 mRNA levels determined by hybridization with a cDNA probe in a series of primary breast tumours. pNR-2 expression was assessed immunohistochemically in a panel of normal tissues. Expression was detected in normal breast, small intestine, and stomach (body and antrum).

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