Growth Factors and Their Receptors

Could prolactin receptor gene polymorphism play a role in pathogenesis of breast carcinoma?

OBJECTIVE

Constitutive activation of various hormone and growth factor receptors is newly recognised as a common cause of tumour development. This study investigated the presence of any mutation or polymorphism of prolactin receptor (PRLR) in 38 patients with breast cancer.

RESEARCH METHODS

Genomic DNA was extracted and PCR amplification was carried out for exon 1-10 of PRLR from tumoral and adjacent non-cancerous breast tissue of tumour specimens from 38 breast cancer patients. PCR products were analysed by SSCP and automatic sequencing for mutations.

RESULTS

For the first time, A150C (Leu-->Ile) transversion at exon 6 of PRLR in tumour tissues, in adjacent non-cancerous breast tissues, and in blood samples of two (5.3%) out of 38 patients with breast cancer were detected. In contrast to this finding, no polymorphism of PRLR in blood samples of 100 normal individuals were found.

CONCLUSION

Polymorphism of prolactin receptors might play a role in mammary carcinogenesis as a consequence of intracellular changes of PRLR signalling.

Best hope or last hope: access to phase III clinical trials of HER-2/neu for advanced stage breast cancer patients

Breast cancer is a major public health problem, with a 12% incidence among women. The over-expression of the proto-oncogene HER-2/neu is associated with 30% of breast and ovarian cancers that are very aggressive and do not respond to standard therapeutic regimens. Entrance into clinical trials can represent the best hope and even the last hope for these patients. Entrance, however, is based on satisfying eligibility criteria. In examining advanced stage breast cancer patients' access to phase III clinical trials for HER-2/neu, two specific arguments regarding eligibility will be addressed. First, if research is to provide the utilitarian goal of the 'greatest good to the greatest number', delineation of the population receiving the 'good', rather than a homogeneous sub-set of this population, must be addressed, along with patients' values and goals, very relevant to determining a 'good life', how to achieve it, and whether a treatment is a part of that process. Second, the 'good' being generated should involve realistic, practical values of quality ways of living with advanced breast cancer and not just increased survival, or cure. Arguments for relaxing criteria are based on an accurate versus over-simplified interpretation of utilitarian principles and concepts of human flourishing. Only through addressing these issues can the true 'good' of clinical trials and research be given to the greatest number of people.

Involvement of prolactin in breast cancer: redefining the molecular targets

The mammary gland is the major target tissue of prolactin (PRL) in mammals. Although this pituitary hormone has been long suspected to be involved in the progression of human breast cancer, the failure of clinical improvement by treatment with dopamine agonists (which lower circulating levels of PRL) rapidly reduced the interest of oncologists concerning a potential role of PRL in the development of breast cancer. Within the last few years, however, several studies reported first, that PRL is also synthesized by mammary epithelial cells, and second that it may exert a proliferative action in an autocrine/paracrine manner. In agreement with a recent epidemiological study, these observations have led to a reconsideration of the role of PRL as an active participant in breast cancer, and are an impetus to redefine the molecular targets of anti-prolactin strategies since dopamine analogs are assumed to be inefficient on extrapituitary PRL synthesis. In this review, we briefly summarize the current knowledge of PRL effects on both normal and tumor mammary cells, and we discuss the most relevant articles supporting the autocrine-paracrine action of PRL in the breast. With the aim of defining putative new molecular targets, we propose an overview of the main PRL receptor signaling cascades known to be triggered by PRL in mammary epithelial cells or, when not available, in other cell types. Finally, because proteolytic fragments of rat PRL have been shown to inhibit the angiogenic process, which may be relevant for preventing the progression of solid tumors such as breast tumors, we discuss the hypothesis that the enzymatic cleavage of human PRL could also represent a new molecular target in the search for alternative strategies in the treatment of breast cancer.

Molecular prognostic markers in breast cancer

Based on the scientific literature, there are several molecular markers which might be used for the prognosis of breast cancer. Possible molecular prognostic markers are: BRCA-1, BRCA-2, p53, erbB oncogenes, loss of heterozygosity (LOH), chromosomal aberrations, microsatellite instability, transforming growth factor alpha (TGFalpha), and the multiple drug resistance (MDR) gene. In this chapter, we discuss the possible role of these prognostic markers in breast cancer.

Leukemia inhibitory factor binds to human breast cancer cells and stimulates their proliferation

Leukemia inhibitory factor (LIF) is a cytokine that was originally described as a differentiation factor of a murine myeloid leukemia cell line and subsequently found to be an important mediator of embryonic development. Although extensively studied in the hematopoietic system, its effects on solid tumors are generally unknown. In the present study we investigated the role of LIF in human breast cancer cells. Using the reverse transcriptase-polymerase chain reaction, we found that the human breast carcinoma MCF-7 cell line expressed the message for both LIF receptor and its signal-transducing protein gp130, suggesting that these receptors might be biologically active. Binding studies with radiolabeled LIF demonstrated that MCF-7 cells interacted with this cytokine, and the ligand binding was specific and time, dose, and temperature dependent. In addition, a Scatchard analysis of the data revealed a single class of high-affinity (Kd 0.27 nM) receptors with a density of approximately 430 sites per cell. MCF-7 cells exposed to LIF internalized and degraded the ligand. LIF stimulated the growth of MCF-7 as well as other estrogen-dependent and independent breast cancer cell lines, but the effect on normal breast epithelial lines was less significant. Likewise, it stimulated colony formation by breast cancer cells obtained from five different breast cancer patients in a dose-dependent fashion. These results overall suggest that human breast tumor cells express functional LIF receptors that play a role in breast cancer cell proliferation.