Long term increased expression of the short form 1b prolactin receptor in PC-3 human prostate cancer cells decreases cell growth and migration, and causes multiple changes in gene expression consistent with reduced invasive capacity

S179D Prolactin Sensitizes Human PC3 Prostate Cancer Xenografts to Anti-tumor Effects of Well-Tolerated Doses of Calcitriol

Calcitriol has been shown to have multiple anti-prostate cancer effects both in vitro and in xenograft models, and associations between low levels of calcitriol and more aggressive forms of prostate cancer have been observed clinically. However, the concentrations of calcitriol required to have a substantive anti-cancer effect in vivo are toxic. In previous work, we had observed that the selective prolactin receptor modulator, S179D PRL, sensitized prostate cancer cells in vitro to physiological concentrations of calcitriol through an ability to increase expression of the vitamin D receptor. Here, we have investigated whether administration of S179D PRL would likewise sensitize androgen-insensitive human PC3 xenografts in vivo and do so without inducing tissue damage akin to hypervitaminosis D. Using low concentrations of both S179D PRL (250 ng/h) and calcitriol (up to 220 pg/h), we found no effect of each alone or in combination on the growth rate of tumors. However, there was increased central tumor death with their combination that was more than additive at 250 ng S179D PRL and 220 pg calcitriol per hour. Both S179D PRL and calcitriol alone were antiangiogenic, but their antiangiogenic effects were not additive. Also, both S179D PRL and calcitriol alone increased the number of apoptotic cells in tumor sections, but their combination reduced the number, suggesting more effective clearance of apoptotic cells. Histopathology of the livers and kidneys showed no changes consistent with hypervitaminosis D. We conclude that dual therapy holds promise as a means to harness the anti-tumor effects of well-tolerated doses of calcitriol.

Orchestration of signaling by structural disorder in class 1 cytokine receptors

BACKGROUND

Class 1 cytokine receptors (C1CRs) are single-pass transmembrane proteins responsible for transmitting signals between the outside and the inside of cells. Remarkably, they orchestrate key biological processes such as proliferation, differentiation, immunity and growth through long disordered intracellular domains (ICDs), but without having intrinsic kinase activity. Despite these key roles, their characteristics remain rudimentarily understood.

METHODS

The current paper asks the question of why disorder has evolved to govern signaling of C1CRs by reviewing the literature in combination with new sequence and biophysical analyses of chain properties across the family.

RESULTS

We uncover that the C1CR-ICDs are fully disordered and brimming with SLiMs. Many of these short linear motifs (SLiMs) are overlapping, jointly signifying a complex regulation of interactions, including network rewiring by isoforms. The C1CR-ICDs have unique properties that distinguish them from most IDPs and we forward the perception that the C1CR-ICDs are far from simple strings with constitutively bound kinases. Rather, they carry both organizational and operational features left uncovered within their disorder, including mechanisms and complexities of regulatory functions.

CONCLUSIONS

Critically, the understanding of the fascinating ability of these long, completely disordered chains to orchestrate complex cellular signaling pathways is still in its infancy, and we urge a perceptional shift away from the current simplistic view towards uncovering their full functionalities and potential. Video abstract.

The progesterone and estrogen modify the uterine prolactin and prolactin receptor expression of hyperprolactinemic mice

The aim of this study was to evaluate the effects of metoclopramide-induced hyperprolactinemia on the prolactin (PRL) and PRL receptor's expression in the uterus of mice. For this purpose, 49 Swiss mice were divided into the following groups: GrSS (non-ovariectomized mice given vehicle); GrMET (non-ovariectomized mice treated with metoclopramide); OvSS (ovariectomized mice given vehicle); OvMET (ovariectomized mice treated with metoclopramide); OvMET+17βE (ovariectomized mice treated with metoclopramide and 17β estradiol); OvMET+MP (ovariectomized mice treated with metoclopramide and micronized progesterone); OvMET+17βE+MP (ovariectomized mice treated with metoclopramide and a solution of 17β estradiol and micronized progesterone). Immunohistochemical analyzes were evaluated semi-quantitatively. Our results showed that GrMET, OvMET+MP, and OvMET+17βE+MP presented strong PRL expression. OvMET and OvMET+17βE presented mild reaction, while GrSS and OvSS presented weak reaction. Concerning PRL receptor, OvMET+MP and OvMET+17βE+MP showed strong reaction; GrMET, OvSS, and OvMET+17βE showed mild reaction; and GrSS and OvMET showed weak reaction. These findings suggest that progesterone alone or in combination with estrogen may increase the expression of uterine PRL and PRL receptor.

Blockade of estrogen-stimulated proliferation by a constitutively-active prolactin receptor having lower expression in invasive ductal carcinoma

A comprehensive understanding of prolactin's (PRL's) role in breast cancer is complicated by disparate roles for alternatively-spliced PRL receptors (PRLR) and crosstalk between PRL and estrogen signaling. Among PRLRs, the short form 1b (SF1b) inhibits PRL-stimulated cell proliferation. In addition to ligand-dependent PRLRs, constitutively-active varieties, missing the S2 region of the extracellular domain (ΔS2), naturally occur. Expression analysis of the ΔS2 version of SF1b (ΔS2SF1b) showed higher expression in histologically-normal contiguous tissue versus invasive ductal carcinoma. To determine the function of ΔS2SF1b, a T47D breast cancer line with inducible expression was produced. Induction of ΔS2SF1b blocked estrogen-stimulated cell proliferation. Unlike intact SF1b, induction of ΔS2SF1b had no effect on PRL-mediated activation of Stat5a. However induction inhibited estrogen's stimulatory effects on serine-118 phosphorylation of estrogen receptor α, serine-473 phosphorylation of Akt, serine-9 phosphorylation of GSK3β, and c-myc expression. In addition, induction of ΔS2SF1b increased expression of the cell cycle-inhibiting protein, p21. Thus, increased expression of ΔS2SF1b, such as we demonstrate occurs with the selective PRLR modulator, S179D PRL, would create a physiological state in which estrogen-stimulated proliferation was inhibited, but differentiative responses to PRL were maintained.

Prolactin and prolactin receptor expression in cervical intraepithelial neoplasia and cancer

Prolactin receptor (PRLR) overexpression could play a role in tumorigenesis. The aim of this study was to determine prolactin (PRL) and PRLR expression in biopsies from patients with precursor lesions and uterine cervical cancer. PRLR expression was analyzed in 63 paraffin-embedded biopsies of uterine cervical tissue. In total, eleven low-grade squamous intraepithelial lesions (LSIL), 23 high-grade squamous intraepithelial lesions (HSIL), 21 uterine cervical cancers (UCC) and 8 normal epithelium (NE) were examined using immunoperoxidase staining and Western blot analysis. Additionally, PRL expression was identified in human cervical cancer serum and tissues. The PRLR expression was found to be significantly increased in cervical cancer in comparison with normal tissue and precursor lesions (P < 0.0003). The presence of the long isoform of the PRLR was observed only in cervical cancer tissues. Serum PRL levels were normal in all samples and local prolactin expression was similar in precursor lesions and cervical cancer by Western blot analysis. Our data suggest a possible role for PRLR in the progression of cervical cancer.

High expression of prolactin receptor is associated with cell survival in cervical cancer cells

BACKGROUND

The altered expression of prolactin (PRL) and its receptor (PRLR) has been implicated in breast and other types of cancer. There are few studies that have focused on the analysis of PRL/PRLR in cervical cancer where the development of neoplastic lesions is influenced by the variation of the hormonal status. The aim of this study was to evaluate the expression of PRL/PRLR and the effect of PRL treatment on cell proliferation and apoptosis in cervical cancer cell lines.

RESULTS

High expression of multiple PRLR forms and PRLvariants of 60-80 kDa were observed in cervical cancer cell lines compared with non-tumorigenic keratinocytes evaluated by Western blot, immunofluorecence and real time PCR. Treatment with PRL (200 ng/ml) increased cell proliferation in HeLa cells determined by the MTT assay at day 3 and after 1 day a protective effect against etoposide induced apoptosis in HeLa, SiHa and C-33A cervical cancer cell lines analyzed by the TUNEL assay.

CONCLUSIONS

Our data suggests that PRL/PRLR signaling could act as an important survival factor for cervical cancer. The use of an effective PRL antagonist may provide a better therapeutic intervention in cervical cancer.

Role of splice variants in the metastatic progression of prostate cancer

AS (alternative splicing) and its role in disease, especially cancer, has come to forefront in research over the last few years. Alterations in the ratio of splice variants have been widely observed in cancer. Splice variants of cancer-associated genes have functions that can alter cellular phenotype, ultimately altering metastatic potential. As metastases are the cause of approximately 90% of all human cancer deaths, it is crucial to understand how AS is dysregulated in metastatic disease. We highlight some recent studies into the relationship between altered AS of key genes and the initiation of prostate cancer metastasis.

Characterization of ductal and lobular breast carcinomas using novel prolactin receptor isoform specific antibodies

BACKGROUND

Prolactin is a polypeptide hormone responsible for proliferation and differentiation of the mammary gland. More recently, prolactin's role in mammary carcinogenesis has been studied with greater interest. Studies from our laboratory and from others have demonstrated that three specific isoforms of the prolactin receptor (PRLR) are expressed in both normal and cancerous breast cells and tissues. Until now, reliable isoform specific antibodies have been lacking. We have prepared and characterized polyclonal antibodies against each of the human PRLR isoforms that can effectively be used to characterize human breast cancers.

METHODS

Rabbits were immunized with synthetic peptides of isoform unique regions and immune sera affinity purified prior to validation by Western blot and immunohistochemical analyses. Sections of ductal and lobular carcinomas were stained with each affinity purified isoform specific antibody to determine expression patterns in breast cancer subclasses.

RESULTS

We show that the rabbit antibodies have high titer and could specifically recognize each isoform of PRLR. Differences in PRLR isoform expression levels were observed and quantified using histosections from xenografts of established human breast cancer cells lines, and ductal and lobular carcinoma human biopsy specimens. In addition, these results were verified by real-time PCR with isoform specific primers. While nearly all tumors contained LF and SF1b, the majority (76%) of ductal carcinoma biopsies expressed SF1a while the majority of lobular carcinomas lacked SF1a staining (72%) and 27% had only low levels of expression.

CONCLUSIONS

Differences in the receptor isoform expression profiles may be critical to understanding the role of PRL in mammary tumorigenesis. Since these antibodies are specifically directed against each PRLR isoform, they are valuable tools for the evaluation of breast cancer PRLR content and have potential clinical importance in treatment of this disease by providing new reagents to study the protein expression of the human PRLR.