Hypoxia and expression of the proapoptotic regulator BNIP3 in cervical cancer

Hypoxia plays a major role in the malignant progression of tumors. Here, we investigate the expression of Bcl-2/adenovirus E1B 19 kd-interacting protein 3 (BNIP3), a proapoptotic Bcl-2 family member, and its relationship to hypoxia in cervical cancer cell lines and clinical samples of cervical cancer. Cervical cancer cell lines were grown under hypoxia or normoxia, and BNIP3 mRNA expression was examined by Northern blot analysis. In 50 patients with cervical cancer, intratumoral oxygen measurement with the Eppendorf electrode and needle biopsies of the tumor were performed. The obtained tissue was subsequently analyzed by immunohistochemistry with an anti-BNIP3 antibody. Cervical cancer tissue collected upon surgery was used for Northern blot analysis of in vivo BNIP3 mRNA expression. BNIP3 mRNA is strongly induced under hypoxic conditions in all cervical cancer cell lines investigated. Furthermore, Northern blot analysis revealed that BNIP3 mRNA is expressed in cervical cancer tissue. Using immunohistochemistry, we demonstrated that BNIP3 protein is expressed in 82% of the investigated cervical cancers and that more advanced tumor stages showed significantly stronger BNIP3 expression. However, we observed no correlation between BNIP3 expression and intratumoral hypoxia. In conclusion, BNIP3 is expressed in different cervical cancer cell lines as well as in clinical samples of cervical cancer. Although BNIP3 is clearly hypoxia-inducible in vitro, our results suggest additional mechanisms of BNIP3 regulation in vivo. Our findings therefore highlight a discrepancy between in vitro models of tumor hypoxia and the complexity of human cancer.

Different T-cell Receptor (TCR) Zeta Chain Expression in Cervical Cancer and its Precursor Lesions

OBJECTIVE

Cervical cancer is associated with infection of epithelial cells with the human papillomavirus (HPV) type 16 and HPV18. A functional signalling machinery in T-cells is required in order to successfully fight and eradicate HPV16+ transformed epithelial cells. One of the key signalling molecules associated with the T-cell receptor (TCR) is the homodimeric zeta chain molecule.

MATERIAL AND METHODS

28 formalin fixed und paraffin embedded samples of cervical tissue with cervical intraepithelial lesions CIN I (n = 3), CIN III (n = 7), invasive cervical carcinoma (CC) (n = 13) and normal cervical tissue (n = 5) has been evaluated for HPV-PCR und zeta chain immunohistochemistry. For immunohistochemistry a monoclonal IgG1 anti TZR zeta chain-antibody (mAb) has been used (clone 6B 10.2, Santa Cruz, Heidelberg, Germany). According to the performed Western-Blot analysis on peripheral blood monocytes (PBMCs) the used mAb has specifically recognized TCR zeta chains.

RESULTS

We show reduced protein zeta chain expression associated with invasive cervical cancer, but not with pre-invasive HPV16-positive lesions or HPV16-negative normal cervix tissue.

CONCLUSIONS

Thus, reduced TCR zeta chain expression is not necessarily linked to a chronic viral infection, nor to the presence of transformed cells, but rather to the stromal invasion of the cancer lesion.

Circulating endothelial progenitor cells are inversely correlated with the median oxygen tension in the tumor tissue of patients with cervical cancer

Tumor hypoxia leads to adaptive responses in cancer cells, including an induction of vasculogenesis initiated by circulating endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs). The aim of the present study was to correlate the number of EPCs and CECs with the oxygenation of cervical cancer. Blood concentrations of EPCs were detected by FACS analysis with antibodies for CD34 and vascular endothelial growth factor receptor 2 (VEGFR2). CECs were evaluated by double staining for 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine-labeled acetylated low density lipoprotein (Di-LDL) and lectin in a cell culture assay. Ten patients with cervical cancer were compared with ten healthy volunteers. Intratumoral oxygen tension was assessed polarographically with the computerized Eppendorf histography system. Analysis of CEC numbers revealed no difference between patients and controls. However, patients had lower concentrations of CD34-positive hematopoietic stem cells (HSCs) but a significantly higher fraction of EPCs related to the number of HSCs (1.09% versus 0.53%). This fraction was significantly inversely correlated to the median oxygen tension (r = -0.74, p = 0.015). Our study shows for the first time a significant inverse correlation between the fraction of EPCs and intratumoral oxygen tension. We conclude that the fraction of EPCs should be further evaluated as a useful and convenient marker in the prediction of tumor tissue oxygenation.

Loss of Apaf-1 expression and resistance to hypoxia-induced apoptosis in cervical cancer

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Background: Clinical observations suggest that intratumoral hypoxia may increase the aggressiveness of tumors through clonal selection of cancer cells that have lost their apoptotic potential. We have shown previously that patients with hypoxic cervical cancers displaying a low apoptosis rate had a significantly worse prognosis compared to all other patients. The aim of this study, therefore, was to investigate the expression of the proapoptotic protein Apaf-1 in cervical cancers and to analyze its relation to intratumoral hypoxia and apoptosis. Methods: 56 patients with cervical cancer (FIGO stage IB to IV) were subjected to pretherapeutical intratumoral pO2 measurement with the Eppendorf electrode after informed written consent was given by each patient. The study was approved by the Ethics Committee of the University of Leipzig. Cervical cancer tissue from these patients was taken by needle core biopsy and analyzed by TUNEL assays as well as by immunohistochemistry with an anti-Apaf-1-antibody. For statistical analysis, Fisher’s exact test was used. Results: Apaf-1 was expressed in 86% of cervical cancers. The median apoptosis rate was 1.0% (range: 0.3– 3.4%). There was no direct correlation between Apaf-1 expression and intratumoral hypoxia. However, in the group of hypoxic cervical cancers (pO2 <10 mmHg) with a low apoptosis rate (<1.0%), 43.8 % (95% CI: 19.8–70.1%) of tumors showed a negative Apaf-1 expression compared to only 2.5% (95% CI: 0.06–13.1%) in non-hypoxic cancers and hypoxic cancers with a high apoptosis rate (p = 0.0003, Fisher’s exact test). Conclusions: While Apaf-1 is expressed in the vast majority of cervical cancers, a significant proportion of tumors with low apoptosis rates despite intratumoral hypoxia showed a loss of Apaf-1 expression. This finding suggests a mechanism by which hypoxic cervical cancers acquire resistance to apoptosis.

No significant financial relationships to disclose.

Hypoxia and expression of the proapoptotic regulator BNIP3 in cervical cancer

Hypoxia plays a major role in the malignant progression of tumors. Here, we investigate the expression of Bcl-2/adenovirus E1B 19 kd-interacting protein 3 (BNIP3), a proapoptotic Bcl-2 family member, and its relationship to hypoxia in cervical cancer cell lines and clinical samples of cervical cancer. Cervical cancer cell lines were grown under hypoxia or normoxia, and BNIP3 mRNA expression was examined by Northern blot analysis. In 50 patients with cervical cancer, intratumoral oxygen measurement with the Eppendorf electrode and needle biopsies of the tumor were performed. The obtained tissue was subsequently analyzed by immunohistochemistry with an anti-BNIP3 antibody. Cervical cancer tissue collected upon surgery was used for Northern blot analysis of in vivo BNIP3 mRNA expression. BNIP3 mRNA is strongly induced under hypoxic conditions in all cervical cancer cell lines investigated. Furthermore, Northern blot analysis revealed that BNIP3 mRNA is expressed in cervical cancer tissue. Using immunohistochemistry, we demonstrated that BNIP3 protein is expressed in 82% of the investigated cervical cancers and that more advanced tumor stages showed significantly stronger BNIP3 expression. However, we observed no correlation between BNIP3 expression and intratumoral hypoxia. In conclusion, BNIP3 is expressed in different cervical cancer cell lines as well as in clinical samples of cervical cancer. Although BNIP3 is clearly hypoxia-inducible in vitro, our results suggest additional mechanisms of BNIP3 regulation in vivo. Our findings therefore highlight a discrepancy between in vitro models of tumor hypoxia and the complexity of human cancer.

Placental localization and expression of the cell death factors BNip3 and Nix in preeclampsia, intrauterine growth retardation and HELLP syndrome

OBJECTIVE

BNip3 and its homologue Nix are pro-apoptotic factors of the Bcl-2-family and are expressed in malignant tumors. In vitro, this expression was shown to be mediated by hypoxia. Recently, it has been shown that placental hypoxia as well as apoptosis are pathogenetic factors for pregnancy-induced hypertensive diseases and intrauterine growth retardation (IUGR). The aim of the study was to analyze placental expression of BNip3 and Nix in pregnancies complicated by preeclampsia, hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome and IUGR.

MATERIAL AND METHODS

Placental tissue was sampled from 10 pregnancies each with preeclampsia, HELLP syndrome, IUGR and gestational age-matched controls. The placental expression of BNip3/Nix has been investigated with immunohistochemistry by the use of specific human BNip3/Nix antibodies.

RESULTS

In cytotrophoblastic cells, the BNip3 expression was strong in the control placentas, but only mediate in the placentas from pregnancies with preeclampsia, IUGR or HELLP syndrome. The intensity of the Nix staining showed a similar pattern. In the syncytiotrophoblast, there was a weak BNip3 staining observable in the control as well as IUGR samples, whereas BNip3 was undetectable in preeclamptic placentas or those with HELLP syndrome. For Nix, only in the preeclampsia a weak staining was detectable, whereas all other probes were negative.

CONCLUSIONS

Our study shows for the first time that the pro-apoptotic proteins BNip3 and Nix are expressed in the human placenta. Pregnancies with placental dysfunction and hypertensive pregnancy disorders with different clinical manifestations are characterized by a significantly decreased expression of BNip3 and Nix. These results suggest that the hypothesis of generally increased placental apoptosis in pregnancy-induced hypertensive disorders caused by disturbed trophoblast invasion has to be partly reconsidered.