Interrelationship of prolactin and its receptor in carcinoma of colon and rectum: a preliminary report

Minireview: prolactin regulation of adult stem cells

Adult stem/progenitor cells are found in many tissues, where their primary role is to maintain homeostasis. Recent studies have evaluated the regulation of adult stem/progenitor cells by prolactin in various target tissues or cell types, including the mammary gland, the prostate, the brain, the bone marrow, the hair follicle, and colon cancer cells. Depending on the tissue, prolactin can either maintain stem cell quiescence or, in contrast, promote stem/progenitor cell expansion and push their progeny towards differentiation. In many instances, whether these effects are direct or involve paracrine regulators remains debated. This minireview aims to overview the current knowledge in the field.

Gene expression patterns unveil a new level of molecular heterogeneity in colorectal cancer

The recognition that colorectal cancer (CRC) is a heterogeneous disease in terms of clinical behaviour and response to therapy translates into an urgent need for robust molecular disease subclassifiers that can explain this heterogeneity beyond current parameters (MSI, KRAS, BRAF). Attempts to fill this gap are emerging. The Cancer Genome Atlas (TGCA) reported two main CRC groups, based on the incidence and spectrum of mutated genes, and another paper reported an EMT expression signature defined subgroup. We performed a prior free analysis of CRC heterogeneity on 1113 CRC gene expression profiles and confronted our findings to established molecular determinants and clinical, histopathological and survival data. Unsupervised clustering based on gene modules allowed us to distinguish at least five different gene expression CRC subtypes, which we call surface crypt-like, lower crypt-like, CIMP-H-like, mesenchymal and mixed. A gene set enrichment analysis combined with literature search of gene module members identified distinct biological motifs in different subtypes. The subtypes, which were not derived based on outcome, nonetheless showed differences in prognosis. Known gene copy number variations and mutations in key cancer-associated genes differed between subtypes, but the subtypes provided molecular information beyond that contained in these variables. Morphological features significantly differed between subtypes. The objective existence of the subtypes and their clinical and molecular characteristics were validated in an independent set of 720 CRC expression profiles. Our subtypes provide a novel perspective on the heterogeneity of CRC. The proposed subtypes should be further explored retrospectively on existing clinical trial datasets and, when sufficiently robust, be prospectively assessed for clinical relevance in terms of prognosis and treatment response predictive capacity. Original microarray data were uploaded to the ArrayExpress database (http://www.ebi.ac.uk/arrayexpress/) under Accession Nos E-MTAB-990 and E-MTAB-1026.

Prolactin gene expression in primary central nervous system tumors

Background

Prolactin (PRL) is a hormone synthesized in both the pituitary gland and extrapituitary sites. It has been associated with the occurrence of neoplasms and, more recently, with central nervous system (CNS) neoplasms. The aim of this study was to evaluate prolactin expression in primary central nervous system tumors through quantitative real-time PCR and immunohistochemistry (IH).

Results

Patient mean age was 49.1 years (SD 15.43), and females accounted for 70% of the sample. The most frequent subtype of histological tumor was meningioma (61.5%), followed by glioblastoma (22.9%). Twenty cases (28.6%) showed prolactin expression by immunohistochemistry, most of them females (18 cases, 90%). Quantitative real-time PCR did not show any prolactin expression.

Conclusions

Despite the presence of prolactin expression by IH, the lack of its expression by quantitative real-time PCR indicates that its presence in primary tumors in CNS is not a reflex of local production.

Colon cancer screening in women

Colorectal cancer is the third leading cause of cancer-related deaths in women. Colorectal cancer is a preventable disease with accepted screening modalities that have been proven to save lives. As women are more likely than men to develop right-sided colon cancers, colonoscopy is the preferred screening test in women. Currently, women are less likely to undergo colorectal cancer screening than men. Frank discussions addressing the fear or embarrassment of endoscopic screening are important in helping women overcome these barriers. Enhanced education of both practitioners and patients targeted to improve colorectal cancer screening adherence will improve early diagnosis and patient survival.

Clinicopathological significance of prolactin receptor expression in colorectal carcinoma and corresponding metastases

The role of human prolactin and its receptor, the prolactin receptor, in colorectal cancer is largely unknown. Our study aimed to assess the prevalence of prolactin receptor expression, its association with clinicopathological variables, as well as its prognostic value, comparing results of primary tissues with those of corresponding metastases. In all, 373 primary colorectal cancer and 171 corresponding metastases were evaluated for prolactin receptor expression by immunohistochemistry using a tissue microarray technique. Immunoreactivity was semiquantitatively scored as either focal (<10% of tumor cells positive), moderate (10-50%), or extensive (>50%). Prolactin receptor expression was related to clinicopathological parameters as well as patient outcome. To substantiate our findings, prolactin receptor expression was additionally assessed in HT-29 and SW-480 colorectal cancer cell lines using western blot. Prolactin receptor expression was observed in 360 out of 373 (97%) primary tumors, with 21 (6%) cases showing focal, 55 (15%) moderate, and 284 (76%) extensive expression, respectively. Extensive prolactin receptor expression was significantly associated with tumor size (P=0.002) and grade (P<0.001) as well as histological subtype (P<0.001). Somer's D coefficients for concordance of primary tumors with corresponding lymph node and distant metastases were D=0.719 (P<0.001) and D=0.535 (P=0.001), respectively. Extensive prolactin receptor expression was significantly associated with disease progression (P=0.03) and cancer-specific survival (P=0.04) in patients with high-grade cancers. In conclusion, prolactin receptor expression is common in colorectal cancer, with high concordance between primary tumors and corresponding metastases. In view of evolving targeted therapy concepts in colorectal cancer, widespread prolactin receptor expression may offer a therapeutic perspective in affected patients.

Hyperprolactinemia and immunohistochemical expression of intracellular prolactin and prolactin receptor in primary central nervous system tumors and their relationship with cellular replication

The role of prolactin (PRL) in the CNS remains uncertain. We evaluated the presence of hyperprolactinemia, intracellular prolactin (ICP), and prolactin receptor (PRL-R) in primary CNS tumors, and their relationship with cellular replication with a prospective cross-sectional study of 82 consecutive patients with primary CNS tumors admitted for neurosurgical resection between October 2003 and September 2005. Patients submitted to a questionnaire, and venous blood samples were obtained for measurement of serum PRL and TSH. Immunohistochemical analyses were performed to evaluate the presence of ICP, PRL-R, and Ki-67. Serum PRL levels ranged from 2 to 70 ng/ml, and hyperprolactinemia was detected in 25 cases (30.5%). ICP was detected in 18 patients (21.9%), in whom PRL ranged from 2 to 32 ng/ml. A positive correlation was found between PRL levels and the presence of ICP (Student's t test, P = 0.022). The PRL-R was observed immunohistochemically in 32 cases (39%). The frequencies of hyperprolactinemia, ICP, and PRL-R were similar across the several histological types of CNS tumors. Ki-67 index was similar in all groups. Hyperprolactinemia and intracellular presence of PRL and PRL-R were common findings in this population, suggesting a role for PRL in CNS tumor genesis.

Expression of prolactin receptor and prolactin in normal and malignant thyroid: a tissue microarray study

OBJECTIVE

There is increasing evidence involving prolactin (PRL) and its receptor (PRLR) in the development of different cancers. The aim of the present study was to investigate the expression of PRLR and PRL in human thyroid tissues.

DESIGN AND METHODS

Using tissue microarray (TMA) by immunohistochemical staining, we examined the expression level of PRLR and PRL in 314 specimens from 71 thyroid cancer patients and 15 normal thyroid samples.

RESULTS

Expression of the PRLR was observed in 93.3% of normal thyroid samples and in 76.1% of all thyroid cancers, while expression of PRL was observed in only 10% of medullary thyroid carcinomas and not at all in the other specimens, whether normal or neoplastic. Moreover, results suggested an overexpression of PRLR in 70% of medullary thyroid carcinomas, whereas 53.3% of poorly differentiated thyroid carcinomas showed a negative pattern of staining (p = 0.014 vs normal).

CONCLUSIONS

Present data revealed, for the first time, a widespread expression of PRLR in normal and neoplastic human thyroid tissues as well as a scarce expression of PRL, observed only in a few medullary thyroid carcinomas. Whether the overexpression of PRLR observed in medullary thyroid carcinomas or the underexpression of PRLR observed in poorly differentiated thyroid carcinomas play a contributory role in the oncogenesis of these tumors remains to be determined.

Opposite association of serum prolactin and survival in patients with colon and rectal carcinomas: influence of preoperative radiotherapy

Prolactin (PRL) is a pleiotropic hormone associated with the progression of various cancers, including colorectal cancer (CRC). Here we investigate whether the association of serum PRL concentration and survival is affected by tumor location and preoperative radiotherapy (PRERT) in patients with CRC cancer. Serum PRL was determined in 82 CRC patients without previous treatment. Patients with PRL concentrations at and above the 75th percentile (high PRL) or below this level (low PRL), had a significant correlation with overall survival determined using the Kaplan-Meier method. In colon cancer, there was an increased risk of mortality when PRL values were at and above the highest quartile (22% vs. 73%; P = 0.01). In contrast, in rectal cancer, high PRL values were associated with a significant overall survival advantage (88% vs. 44%; P = 0.05), which became more significant (100% vs. 34%; P = 0.005) when only rectal cancer patients receiving PRERT were compared. These findings suggest that tumor location and adjuvant radiotherapy influence the association between circulating PRL and survival in CRC.

Prolactin as a local growth promoter in patients with locally advanced tongue cancer: GCRI experience

BACKGROUND

The purpose of this study was to assess the role of prolactin (PRL) in men with locally advanced tongue cancer.

METHODS

Circulating PRL was assayed immunoradiometrically in pretherapeutic and sequential blood samples of 99 patients with locally advanced tongue cancer. Patients were followed for 3 years or until their death within a stipulated time. Immunohistochemical localization of PRL was performed on formalin-fixed paraffin-embedded tissue sections. Tumoral prolactin receptors (PRLR) were estimated by ligand binding assay; the expression of PRL mRNA and PRLR mRNA were carried out by reverse transcriptase polymerase chain reaction (RT-PCR). Furthermore, PRL amplimer was sequenced and compared with human pituitary PRL amplimer.

RESULTS

Pretherapeutic PRL levels were significantly higher in patients with locally advanced tongue cancer compared with controls (p =.01). Thirty-four percent (34 of 99) of the patients had hyperprolactinemia (PRL >/=15.0 ng/mL). Univariate survival analysis showed that patients with pretherapeutic hyperprolactinemia had a significantly shorter overall survival than patients with pretherapeutic PRL <15.0 ng/mL serum (p =.0009). In multivariate analysis, PRL emerged as the most significant independent prognostic factor influencing overall survival. Furthermore, changes in serial PRL levels showed excellent correlation with response to therapy and progression of disease. Forty-four percent (24 of 54) of the tumors showed positive immunoreactivity with PRL antibody, indicating that PRL or a molecule similar to it is produced by tongue tumors. PRL mRNA expression was seen in 85% (43 of 50) of the tumors and confirmed the de novo synthesis of PRL. Sequence analysis of the 234 bp PRL amplimer revealed that the sequence was homologous to exon 5 of pituitary PRL mRNA. The action of PRL is mediated by PRLR, and it was observed that the PRLR positivity by ligand binding assay was 33%. The expression of PRLR mRNA by RT-PCR showed two forms of PRLR mRNA (ie, intermediate form [500-600 bp] seen in 82% (41 of 50 ) of the tumors and the long form [800-900 bp] seen in 36% (18 of 50) of the tumors. In 82% (41 of 50) of the tumors, either the intermediate or long form was seen.

CONCLUSIONS

This multifaceted study of PRL suggests that tongue cancer cells produce PRL, and this ectopically produced PRL might be acting as a major local growth promoter by means of autocrine and paracrine mechanisms. Looking at its prognostic value and correlation with disease activity, it may provide new insights into treatment of tongue cancer.

Lack of association between hyperprolactinemia and colon carcinoma

Two recent studies reported that many patients with colorectal carcinoma have elevated serum prolactin (PRL) concentrations and have suggested ectopic PRL secretion as the cause. In the present study, serum PRL was minimally elevated in 16 of 116 colon cancer patients and 2 of 25 control subjects; medications or chemotherapy appeared to be responsible for the PRL elevations in 11 of 16 cancer patients. Serum PRL was not correlated with either plasma carcinoembryonic antigen or disease stage. Preoperative and postoperative serum PRL concentrations were similar in 26 evaluated patients. None of 19 colorectal tumors was positive for PRL staining by immunohistochemistry. Thus, we could not confirm previous reports of frequent hyperprolactinemia in patients with colorectal cancer; factors such as medications, anxiety, pain, and nausea may have raised serum PRL in these earlier studies. Serum PRL is not a useful marker for colon carcinoma, at least in patients in the United States.

Cell surface molecules and their prognostic values in assessing colorectal carcinomas

OBJECTIVE

Carcinomas of the colon and rectum are the third leading cause of cancer-related deaths. Although advances in the surgical treatment of primary colorectal cancers have lead to improvements in patient survival at early tumor stages, treatment of more progressive cancers has not resulted in dramatic improvements in patient survival. However, the selection of patient subgroups based on their prognosis and other characteristics could result in improved outcomes from adjuvant therapies in patients with Dukes B and C carcinomas.

METHODS

The authors reviewed the available data on the value of cell surface molecules in assessing the prognosis of colorectal carcinomas, paying specific attention to the evaluation of statistical analysis and multivariate procedures.

RESULTS

Cell surface molecules have been identified on colorectal carcinoma cells whose expression appears to be related to malignant transformation, tumor progression, or patient prognosis. Among these cell surface molecules, various cell adhesion molecules, growth factor receptors, proteinases, and their receptors and inhibitors have been identified as potentially useful prognostic markers.

CONCLUSIONS

Although data exist on the prognostic values of certain cell surface markers, the use of multivariate analysis for the identification of valuable prognostic factors remains uncommon. Using reproducible and standardized multivariate analysis procedures, new tumor markers should be carefully examined for their biologic and prognostic relevance before being considered as potentially useful in the management of colorectal cancers.

Colorectal cancer recurrence during pregnancy--unique and poorly understood clinical entity: report of a case

The detection of primary or recurrent colorectal cancer during pregnancy is a rare event. Early diagnosis is difficult, because symptoms are often attributed to pregnancy. Here we describe a case of recurrent adenocarcinoma of the colon in a 23-year-old pregnant patient. The relationship between various hormonal and immunological changes of pregnancy and colorectal cancer is discussed.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Prognostic value of insulin-like growth factor-1 receptors in patients with colon/rectal cancer: correlation with plasma prolactin

Prognostic value of IGF-1 receptors (IGF-1R) was evaluated and compared with circulating prolactin (PRL) in 59 patients with Dukes B or C colon/rectal cancer. IGF-1R was estimated by radioligand binding assay and PRL was estimated by immunoradiometric assay. Eighty-five percent (50/59) of patients had IGF-1R- tumours while IGF-1R positivity was observed in only 15% (9/59) of patients. None of the clinicopathological parameters showed any association with IGF-1R status. No significant difference was observed in overall survival period between patients with IGF-1R+ tumours and those with IGF-1R- tumours. However, a significant difference in overall survival time was observed between patients with PRL < 20.0 and > 20.0 ng/ml plasma (X2 = 4.70, df = 1, P < 0.05). In bivariate analysis, patients with IGF-1R- tumours and concomitant hyperprolactinemia had unfavourable prognosis compared to their counterpart (X2 = 4.21, df = 1, P < 0.05). We conclude that there was a trend of better overall survival in patients with IGF-1R+ tumours, and PRL < 20.0 ng/ml plasma when compared to patients with IGF-1R- tumours, and PRL > 20.0 ng/ml plasma. Further, IGF-1R negativity in conjunction with hyperprolactinemia could be used as an indicator of unfavourable prognosis in patients with Dukes B or C colon/rectal cancer.