Prognosis in human glioblastoma based on expression of ligand growth hormone-releasing hormone, pituitary-type growth hormone-releasing hormone receptor, its splicing variant receptors, EGF receptor and PTEN genes

Abstract

Purpose: Glioblastoma (GB) is the most frequent brain tumor. Despite recent improvement in therapeutic strategies, the prognosis of GB remains poor. Growth hormone-releasing hormone (GHRH) may act as a growth factor; antagonists of GHRH have been successfully applied for experimental treatment of different types of tumors. The expression profile of GHRH receptor, its main splice variant SV1 and GHRH have not been investigated in human GB tissue samples.

Methods: We examined the expression of GHRH, full-length pituitary-type GHRH receptor (pGHRHR), its functional splice variant SV1 and non-functional SV2 by RT-PCR in 23 human GB specimens. Epidermal growth factor receptor (EGFR) and phosphatase and tensin homolog gene (PTEN) expression levels were also evaluated by quantitative RT-PCR. Correlations between clinico-pathological parameters and gene expressions were analyzed.

Results: Expression of GHRH was found to be positive in 61.9 % of samples. pGHRH receptor was not expressed in our sample set, while SV1 could be detected in 17.4 % and SV2 in 8.6 % of the GB tissues. In 65.2 and 78.3 % of samples, significant EGFR over-expression or PTEN under-representation could be detected, respectively. In 47.8 % of cases, EGFR up-regulation and PTEN down-regulation occurred together. Survival was significantly poorer in tumors lacking GHRH expression. This worse prognosis in GHRH negative group remained significant even if SV1 was also expressed.

Conclusion: Our study shows that GHRH and SV1 genes expressed in human GB samples and their expression patterns are associated with poorer prognosis.

Fig. 1

GHRH ligand and receptor expressions in GB samples. Representative gel photos of mRNA expression of a pGHRHR, b GHRH, c splicing variant, SV1; + positive control (human pituitary), − negative control; No. 1–8 GB samples

Fig. 2

Correlation between expression of mRNA of GHRH ligand and receptor SV1 and overall survival of the patients with newly diagnosed GB. a Correlation between GHRH expression and overall survival of the patients with newly diagnosed GB. Gray, dashed curve shows GHRH negative patients’ survival analysis; black, continuous curve represents GHRH positive cases (p = 0.004). b Correlation between GHRH and SV1 expressions and overall survival of the patients with newly diagnosed GB. Gray, dashed curve shows GHRH negative, SV1 positive patients’ survival analysis; black dashed curve shows GHRH negative SV1 negative cases, gray continuous curve GHRH positive, SV1 positive cases; black, continuous curve represents GHRH positive, SV1 negative cases. (p = 0.008) Kaplan–Meier and log rank (Mantel–Cox) regression tests were used for survival analysis

Fig. 3

Correlation between expression of mRNA of GHRH ligand and receptor SV1 and overall survival of the patients with newly diagnosed GBs and recurrent GBs together. a Correlation between GHRH expression and overall survival of the patients with newly diagnosed GBs and recurrent GBs together (Group 1 and Group 2). Gray, dashed curve shows GHRH negative; black continuous curve represents GHRH positive cases (p = 0.008). b Correlation between GHRH and SV1 expression and overall survival of the patients with newly diagnosed GBs and recurrent GBs together (Group 1 and Group 2). Gray, dashed curve shows GHRH negative, SV1 positive patients’ survival analysis; black dashed curve shows GHRH negative SV1 negative cases, gray continuous curve GHRH positive, SV1 positive cases; black, continuous curve represents GHRH positive, SV1 negative cases. (p = 0.038). Kaplan–Meier and log rank (Mantel–Cox) regression tests were used for survival analysis