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Background: Neuroendocrine (NE) differentiation in prostate cancer has been correlated with a poor prognosis and hormone refractory disease. In a previous report, we demonstrated the presence of immunoreactive cytoplasmic hypoxia inducible factor 1alpha (HIF1alpha), in both benign and malignant NE prostate cells. HIF1alpha and HIF1beta are two subunits of HIF1, a transcription factor important for angiogenesis. The aim of this study was to elucidate whether the cytoplasmic stabilization of HIF1alpha in androgen independent NE differentiated prostate cancer is due to the presence of certain HIF1alpha isoforms., Methods: We studied the HIF1alpha isoforms present in 8 cases of benign prostate hyperplasia (BPH) and 43 cases of prostate cancer with and without NE differentiation using RT-PCR, sequencing analysis, immunohistochemistry and in situ hybridization., Results: We identified multiple isoforms in both benign and malignant prostate tissues. One of these isoforms, HIF1alpha1.2, which was previously reported to be testis specific, was found in 86% of NE-differentiated prostate tumors, 92% of HIF1alpha immunoreactive prostate tumors and 100% of cases of benign prostate hyperplasia. Immunohistochemistry and in situ hybridization results showed that this isoform corresponds to the cytoplasmic HIF1alpha present in androgen-independent NE cells of benign and malignant prostate tissue and co-localizes with immunoreactive cytoplasmic HIF1beta., Conclusion: Our results indicate that the cytoplasmic stabilization of HIF1alpha in NE-differentiated cells in benign and malignant prostate tissue is due to presence of an HIF1alpha isoform, HIF1alpha1.2. Co-localization of this isoform with HIF1beta indicates that the HIF1alpha1.2 isoform might sequester HIF1beta in the cytoplasm.

Background: Oct 3/4 (Octamer 3/4), a member of POU family has been considered as an important stem cell marker and essential transcription factor during human embryogenesis. In recent years, there have also been reports on presence of Oct 3/4 in differentiated benign and malignant human cells. The objective of this study was to investigate the transcription and the protein expression of Oct 3/4 isoforms in prostate cancer and benign prostate tissue., Methods: Thirty sex adenocarcinomas and eight cases of benign prostate hyperplasia were studied. The transcription of Oct 3/4 was analyzed using RT-PCR approach associated with restriction digestion analysis. Oct 3/4 protein expression was studied by immunohistochemistry on paraffin sections using two different antibodies., Results: We identified only the transcript 2 of Oct 3/4 in prostate tumors and benign prostate hyperplasia. Immunohistochemistry verified these results, demonstrating only cytoplasmic localization of Oct 3/4. Transcription of type 1 of Oct 3/4 as well as protein expression with nuclear localization of Oct 3/4 isoform 1 were not detected. Oct 3/4 immunopositive tumors were also displayed neuroendocrine differentiation and showed androgen receptor immunopositivity. The stem cell markers CD44 and CD117 were not detected in Oct 3/4 immunopositive cells., Conclusion: Our results indicate that only the cytoplasmic isoform 2 of Oct 3/4 is present in prostate cancer and benign prostate hyperplasia. The malignant and benign prostate cells, which are immunopositive for variant 2 of Oct 3/4, lack other stem cell markers supporting previously published data that variant 2 of Oct 3/4 is not a pluripotency marker.

Background: Hypoxia induces increased tumor growth by promoting angiogenic and glycolytic pathways. Tumors expressing hypoxia-inducible factor-1alpha (HIF-1alpha), an important transcriptional activator of oxygen-regulated genes, are resistant to chemotherapy and radiotherapy. The major challenge in prostate cancer therapy today is to gain a better understanding of the development of hormone-refractory tumors, which is often characterized by neuroendocrine differentiation. Here we studied the expression of HIF-1alpha and HIF-2alpha in neuroendocrine cells of the benign prostate and in prostate cancer., Methods: Tissue sections from 30 patients who underwent radical prostatectomy and from 21 patients operated by transurethral resection of the prostate were selected for immunohistochemical analysis for expression of HIF-1alpha, HIF-2alpha, androgen receptor (AR), neuroendocrine markers (chromogranin A, synaptophysin), and two gene products downstream of HIF-1alpha: VEGF and GAPDH., Results: Immunoreactive HIF-1alpha was detected in a subpopulation of AR-negative neuroendocrine cells in benign and malignant prostate tissue. Analysis of serial sections showed that the levels of expression of GAPDH and VEGF proteins are increased in AR-negative malignant neuroendocrine cells expressing HIF-1alpha. In situ-hybridization indicated that HIF-1alpha mRNA levels are not higher in neuroendocrine prostate cancer cells relative to corresponding non-neuroendocrine tumor cells. We also demonstrated induced stabilization of nuclear HIF-1alpha in LNCaP cells by hypoxia and long-term stimulation with interleukin-6. Focal HIF-2 expression was detected in benign neuroendocrine-like cells and in malignant prostatic cells., Conclusions: The expression of HIF-1alpha and HIF-2alpha in prostate cancer has been confirmed, but we also identified immunoreactive HIF-1alpha and downstream gene products in benign and malignant prostate neuroendocrine cells., ((c) 2007 Wiley-Liss, Inc.)