Hypoxia upregulates osteopontin expression in NIH-3T3 cells via a Ras-activated enhancer

The kinetics of transcriptomic changes induced by cigarette smoke in rat lungs reveals a specific program of defense, inflammation, and circadian clock gene expression

Gene expression profiling in animal models exposed to cigarette mainstream smoke (CS) shapes up as a promising tool for investigating the molecular mechanisms involved in the onset and development of CS-related disease and may aid in the identification of disease candidate genes. Here we report on differential gene expression in lungs of rats exposed for 2, 7, and 13 weeks to 300 and 600 microg total particulate matter/l CS with sacrifice 2, 6, or 20 h after the last exposure. Regarding antioxidant and xenobiotic-metabolizing (phase I/II) enzymes, a stereotypic, mostly transient, expression pattern of differentially expressed genes was observed after each exposure period. The expression patterns were generally dose dependent for antioxidant and phase II genes and not dose dependent for phase I genes at the CS concentrations tested. However, with increasing length of exposure, there was a distinct, mostly sustained and dose-sensitive, expression of genes implicated in innate and adaptive immune responses, clearly pointing to an emerging inflammatory response. Notably, this inflammatory response included the expression of lung disease-related genes not yet linked to CS exposure, such as galectin-3, arginase 1, and chitinase, as well as genes encoding proteolytic enzymes. Finally, our experiments also revealed a CS exposure-dependent shift in the cyclical expression of genes involved in controlling the circadian rhythm. Altogether, these results provide further insight into the molecular mechanisms of CS-dependent disease onset and development and thus may also be useful for defining CS-specific molecular biomarkers of disease.

Plasma osteopontin levels in patients with head and neck cancer and cervix cancer are critically dependent on the choice of ELISA system

BACKGROUND

The tumor-associated glycoprotein osteopontin (OPN) is discussed as a plasma surrogate marker of tumor hypoxia and as an indicator of the presence of pleural mesothelioma in asbestos-exposed individuals. The clinical introduction of plasma OPN measurements requires the availability of a reliable enzyme-linked immunosorbence assay (ELISA).

METHODS

We compared previously described and currently available ELISA systems on 88 archival plasma samples obtained from patients with head and neck or cervix cancer between 20 days before and 171 after the start of radiotherapy.

RESULTS

Median (range) plasma OPN levels were 667 (148.8-2095) ng/ml and 9.8 (3.5-189.5) ng/ml for a previously described and a newly marketed assay, respectively. Although results for different assays were significantly correlated (r = 0.38, p < 0.05, Spearman rank test), between-assay factors ranged from 2.0 to 217.9 (median 74.6) in individual patients. OPN levels in cervix cancer patients were comparable to those of head and neck cancer patients.

CONCLUSION

Commercially available OPN ELISA systems produce different absolute plasma OPN levels, compromising a comparison of individual patient data with published results. However, different assays appear to have a similar capacity to rank patients according to plasma OPN level. A review of literature data suggests that plasma OPN levels measured even with identical ELISA systems can only be compared with caution.

Strain and tumour specific variations in the effect of hypoxia on osteopontin levels in experimental models

PURPOSE

To investigate the relationship between tumour hypoxia and serum and tumour osteopontin (OPN) levels.

MATERIALS AND METHODS

Experiments were performed in CDF1 or C3H/Km mice implanted with a C3H mammary carcinoma (CDF1) or SCCVII squamous cell carcinoma (C3H/Km), respectively. Mice were either untreated or gassed with 10% oxygen for 1-72 h. Serum and tumour OPN levels were measured with an ELISA and tumour OPN mRNA levels using RT-PCR. Tumour oxygenation was estimated using the Eppendorf histograph with the percentage of pO(2) values <or=5 mm Hg (HF5) as the endpoint.

RESULTS

OPN levels were 50-fold higher in the serum of non-tumour bearing CDF1 mice compared to C3H/Km mice. A tumour related increase in serum OPN levels was observed in CDF1 but not in C3H/Km mice. Low oxygen breathing increased HF5 in both tumour models and in the C3H mammary carcinoma model both serum and tumour OPN decreased after prolonged hypoxia (24h and more). When 12h of hypoxia was followed by 24h reoxygenation there was a twofold increase in serum OPN levels. No changes were observed in the SCCVII model. No changes in tumour OPN mRNA expression were observed during hypoxia and reoxygenation in these tumour models.

CONCLUSION

Clear strain and tumour specific differences in the effect of hypoxia on OPN levels have been observed in two different mouse tumour models. These data emphasize the complexity in the relationship between poor oxygenation (and/or reoxygenation) of tumours and serum levels of OPN.

Differential regulation of angiogenic genes in diabetic wound healing

Wound healing is a complicated biological process that involves interactions of multiple cell types, various growth factors, their mediators, and the extracellular matrix proteins. In this study, we have studied the differential regulation of angiogenic genes during wound healing in transgenic (Lepr -/-) diabetic mice and non-diabetic mice. Under aseptic conditions, 8 mm full thickness cutaneous wounds were created on either side of the mid-dorsal. Wound tissues were studied at 4, 7, and 11 days post-wounding and healing was assessed by histology. The pathway-specific gene array data demonstrated differential regulation of growth factors, transcription factors, and other related genes, such as fibroblast growth factors and their receptors. The extracellular matrix protein osteopontin (OPN), an important component of cellular immunity and inflammation, showed higher expression in non-diabetic wounds after 4 days post-wounding, whereas its expression was at basal level in diabetic wounds. OPN expression remained upregulated in non-diabetic wounds at day 7 post-wounding and was downregulated to basal level at day 11 post-wounding. However, expression of OPN was upregulated in diabetic wounds at day 7 post-wounding and remained constitutively higher at day 11 post-wounding. OPN expression was concomitant with the extent of healing as assessed by histology at the corresponding sampling point. This finding suggests that OPN might be playing a crucial role in the early events of the wound healing and its delayed expression may be in part responsible for the delayed healing of wounds in diabetic mice.

An evaluation of tumor oxygenation and gene expression in patients with early stage non-small cell lung cancers

BACKGROUND

To directly assess tumor oxygenation in resectable non-small cell lung cancers (NSCLC) and to correlate tumor pO2 and the selected gene and protein expression to treatment outcomes.

METHODS

Twenty patients with resectable NSCLC were enrolled. Intraoperative measurements of normal lung and tumor pO2 were done with the Eppendorf polarographic electrode. All patients had plasma osteopontin measurements by ELISA. Carbonic anhydrase-IX (CA IX) staining of tumor sections was done in the majority of patients (n = 16), as was gene expression profiling (n = 12) using cDNA microarrays. Tumor pO2 was correlated with CA IX staining, osteopontin levels, and treatment outcomes.

RESULTS

The median tumor pO2 ranged from 0.7 to 46 mm Hg (median, 16.6) and was lower than normal lung pO2 in all but one patient. Because both variables were affected by the completeness of lung deflation during measurement, we used the ratio of tumor/normal lung (T/L) pO2 as a reflection of tumor oxygenation. The median T/L pO2 was 0.13. T/L pO2 correlated significantly with plasma osteopontin levels (r = 0.53, P = 0.02) and CA IX expression (P = 0.006). Gene expression profiling showed that high CD44 expression was a predictor for relapse, which was confirmed by tissue staining of CD44 variant 6 protein. Other variables associated with the risk of relapse were T stage (P = 0.02), T/L pO2 (P = 0.04), and osteopontin levels (P = 0.001).

CONCLUSIONS

Tumor hypoxia exists in resectable NSCLC and is associated with elevated expression of osteopontin and CA IX. Tumor hypoxia and elevated osteopontin levels and CD44 expression correlated with poor prognosis. A larger study is needed to confirm the prognostic significance of these factors.

Relationship between radiobiological hypoxia in a C3H mouse mammary carcinoma and osteopontin levels in mouse serum

PURPOSE

To investigate the possible relationship between radiobiological hypoxia in a C3H mouse mammary carcinoma and osteopontin (OPN) levels measured in mouse serum.

MATERIAL AND METHODS

Experiments were performed in CDF1 mice that were either non-tumour bearing or with different sized tumours implanted in the right rear foot. Osteopontin levels in extracted mouse blood serum and tissue from the transplanted tumours were measured using an ELISA assay. The tumour oxygenation status was estimated using the Eppendorf Histograph and the fraction of oxygen partial pressure (pO2) values =5 mm Hg (HF5) was calculated. Necrosis was measured in haematoxylin and eosin-stained sections. Tumour hypoxia was increased by placing animals in a low-oxygen (10%) environment. Single radiation doses (240 kV x-rays) were given locally to tumours under ambient or clamped conditions and response assessed using a tumour control assay.

RESULTS

Serum OPN levels increased linearly with increasing tumour volume and this increase correlated with tumour OPN. HF5 and necrosis also increased with increasing tumour volume, but this increase was non-linear. Converting the HF5 results into equivalent tumour volume gave results that were directly correlated to OPN serum levels. Placing mice in a 10% oxygen environment for 12 hours significantly increased HF5. However, serum OPN only increased if reoxygenation occurred before measurement. Radiobiological hypoxic fraction in this tumour model did not change with increasing tumour size, but the total number of hypoxic cells did increase.

CONCLUSIONS

These findings suggest that serum OPN measurement may predict the proportion of hypoxic cells in this tumour model, although increased serum OPN levels simply resulting from an increased tumour burden can not be ruled out.