Identification of specific microRNA-messenger RNA regulation pairs in four subtypes of breast cancer

Four subtypes of breast cancer, luminal A, luminal B, basal-like, human epidermal growth factor receptor-enriched, have been identified based on gene expression profiles of human tumours. The goal of this study is to find whether the same groups' genes would exhibit different networks among the four subtypes. Differential expressed genes between each of the four subtypes and the normal samples were identified. The overlaps between the four groups of differentially expressed genes were used to construct regulations networks for each of the four subtypes. Univariate and multivariate Cox regressions were employed to test the genes in the four regulation networks. This study demonstrated that the common genes in four subtypes showed different regulation. Also, the hsa-miR-182 and decorin pair performs different functions among the four subtypes of breast cancer. The result indicated that heterogeneity of breast cancer is not only reflected in the different expression patterns among different genes, but also in the different regulatory networks of the same group of genes.

Human germ cell tumours: expression of gamma-glutamyl transpeptidase and sensitivity to cisplatin

Previous studies have shown that the enzyme-glutamyl transpeptidase (GGT) is essential for the nephrotoxicity of cisplatin. This study was designed to determine whether GGT activity is necessary for the therapeutic effect of the drug. The relationship between GGT expression and clinical response to platinum-based chemotherapy was examined in 41 human germ cell tumours. Sections of formalin-fixed, paraffin-embedded tumours were immunohistochemically stained with an antibody directed against human GGT. There was no expression of GGT in any of the 17 seminomas or four dysgerminomas; whereas, 12/12 ovarian yolk sac tumours and 4/4 embryonal carcinomas of the testis were GGT-positive. In stage I tumours fewer tumour cells expressed GGT than in later stage tumours. In four germ cell tumours of mixed histology, the seminomatous and dysgerminoma areas were GGT-negative while the areas of the tumour with yolk sac or embryonal histology contained GGT-positive tumour cells. The patients with seminomas or dysgerminomas who were treated with cisplatin-based chemotherapy, all had a complete response despite the absence of GGT expression in these tumours. Fifteen of the 16 patients with yolk sac or embryonal carcinomas received cisplatin-based chemotherapy following surgery. Twelve had a complete response, while three failed to respond to platinum-based therapy. There was no correlation between the level of GGT-expression and response to therapy in this group. Three of the four patients with tumours of mixed histology were treated with cisplatin-based therapy, and had a complete response. Therefore, expression of GGT is not necessary for the therapeutic effect of cisplatin in germ cell tumours. The results from this study suggest that systemic inhibition of GGT would inhibit the nephrotoxic side-effect of cisplatin without interfering with its activity towards germ cell tumours.

Labelling indices in human tumours: to apply corrections or not--that is the question

The advent of halogenated pyrimidines (bromodeoxyuridine, BrdU; idoxuridine, IdU) and antibodies to recognize them has opened new horizons for the measurement of proliferation in human tumours. These precursors of DNA can be given to patients and a single biopsy can be taken to measure in a flow cytometer both the fraction of labelled cells and their rate of movement through the S phase. From these two parameters the potential doubling time, T(POT), can be calculated. To measure both parameters simultaneously a compromise is made in the time of assessing the labelling index (LI). LI should ideally be assessed after a very short interval, e.g. 0.5-1 h, to avoid the contaminating influence of any cells dividing between injection and biopsy. However, an interval of 4-8 h is considered necessary to assess T(S) from the relative movement of cells through the S phase. Several techniques exist to correct for cell division if the interval is long. The simplest correction, which only corrects for the division of labelled cells, is most widely used. Downward correction factors of at least 10% are commonly applied, reducing the observed LI values. In this paper we illustrate graphically the dependence of the appropriate correction factor on various cell kinetic parameters. The duration of G2 is the most critical parameter for both the size and direction of any correction factor. The G2 phase has previously been shown to be about three times longer in human tumours than in rodents. If G2+M is as long as 6 h, the main artefact of the intervals between injection and biopsy up to 7 h is that the observed LI is too low because of division of unlabelled G2 cells. A correction of up to 10% is needed but in an upward direction. A nomogram of probable correction factors as a function of sampling interval is provided. We show from flow cytometric data that G2+M may be shorter than 4 h for head and neck tumours. It is recommended that the correction factor established by gating the flow histogram should always be checked against this nomogram, or that no correction factor should be applied. We have used this mathematical approach to re-evaluate two sets of published LI data for rectal and colorectal tumours. We show that the mathematical correction of each data point leads to a 30% increase in the median value, compared to the simple gating procedure. We question whether other of the published series of LI values gained with BrdU or IdU may also substantially underestimate the true LI values, if a simple gating procedure has been used in an attempt to reduce the impact of divided S phase cells.