Multifaceted role of hair follicle dermal cells in bioengineered skins

BACKGROUND

The method of generating bioengineered skin constructs was pioneered several decades ago; nowadays these constructs are used regularly for the treatment of severe burns and nonhealing wounds. Commonly, these constructs are comprised of skin fibroblasts within a collagen scaffold, forming the skin dermis, and stratified keratinocytes overlying this, forming the skin epidermis. In the past decade there has been a surge of interest in bioengineered skins, with researchers seeking alternative cell sources, or scaffolds, from which constructs can be established, and for more biomimetic equivalents with skin appendages.

OBJECTIVES

To evaluate whether human hair follicle dermal cells can act as an alternative cell source for engineering the dermal component of engineered skin constructs.

METHODS

We established in vitro skin constructs by incorporating into the collagenous dermal compartment: (i) primary interfollicular dermal fibroblasts, (ii) hair follicle dermal papilla cells or (iii) hair follicle dermal sheath cells. In vivo skins were established by mixing dermal cells and keratinocytes in chambers on top of immunologically compromised mice.

RESULTS

All fibroblast subtypes were capable of supporting growth of overlying epithelial cells, both in vitro and in vivo. However, we found hair follicle dermal sheath cells to be superior to fibroblasts in their capacity to influence the establishment of a basal lamina.

CONCLUSIONS

Human hair follicle dermal cells can be readily interchanged with interfollicular fibroblasts and used as an alternative cell source for establishing the dermal component of engineered skin both in vitro and in vivo.

Macroprolactin(s): composition and reactivity in immunoassays and laboratory interpretation of results of an unusual patient serum

Background: Macroprolactin is a high molecular mass complex of prolactin that may be the cause of elevated serum prolactin as determined by immunoassay. The composition of macroprolactin and its reactivity in immunoassays are variable but the complex has minimal bioactivity in vivo. Hyperprolactinaemia due to unrecognized macroprolactinaemia can lead to misdiagnosis and mistreatment.

Methods: Serum from a patient with an unusual pattern of immunoreactivity was distributed to three users of each of the most popular immunoassays represented in the UK National External Quality Assessment Scheme (NEQAS) for prolactin. Clinical details were provided and participating centres were invited to investigate the prolactin content of the specimen according to their local protocol, and to comment on their results. The nature of the macroprolactin in the specimen was investigated in detail by gel filtration chromatography of the native serum and of the serum after adsorption of IgG with protein A, and by affinity chromatography with concanavalin A.

Results: Gel filtration studies revealed two peaks of macroprolactin in this serum. These macroprolactins were shown to be different in their IgG content and degree of glycosylation. All eight immunoassays reacted strongly with the macroprolactin present. The majority (78%) of centres that interpreted their results either demonstrated the presence of macroprolactin in the specimen, or suggested it as a likely cause of the hyperprolactinaemia. However, two centres inappropriately excluded macroprolactinaemia as the cause of the elevated prolactin, and a further two did not consider it at all. Data from previous UK NEQAS distributions (between 1996 and 2003) of macroprolactin containing sera are presented which suggest that the frequency of recognition of macroprolactin as a possible cause of hyperprolactinaemia has increased over time.

Conclusions: Very high molecular mass forms of prolactin and the presence of multiple molecular mass forms, as detected in the case presented here, are uncommon. Also, the pattern of immunoreactivity reported in this specimen was unusual as most macroprolactins studied previously react less strongly in, for example, the Bayer ADVIA Centaur assay compared to the Roche E170 assay. Both peaks of macroprolactin in this serum reacted in all assays tested. This case highlights the variable nature and immunoreactive behaviour of macroprolactin species.

Analysis of the intra- and intertumoral heterogeneity of hypoxia in pancreatic cancer patients receiving the nitroimidazole tracer pimonidazole

Background:

Hypoxia is thought to be an adverse feature of pancreatic cancer, but direct measurement in patients is technically challenging. To address this, we characterised the intra/interpatient heterogeneity of hypoxia in surgical specimens from patients who received the 2-nitroimidazole tracer pimonidazole pre-operatively.

Methods:

Pimondazole was given intravenously 16–20 h before pancreatectomy, and the extent and intratumoral heterogeneity of hypoxia determined by image analysis applied to multiple tissue blocks stained by immunohistochemistry. Intra/interpatient heterogeneity was estimated by variance component analysis.

Results:

Pimonidazole staining was analysed in 10 tumours. The extent of labelling varied amongst patients (0–26%), with a broader range of hypoxia in the epithelial (1–39%) compared with the stromal (1–13%) compartments. Variance component analysis demonstrated greater inter- than intrapatient variability of hypoxia, and that multiple (4–5) tumour sections are required to provide a consistent evaluation of its extent in individual tumours.

Conclusions:

There is significant intra- and intertumoral heterogeneity of hypoxia in pancreatic cancers, and these do not appear to be generally more hypoxic than other cancer types. This study establishes the feasibility to assess hypoxia in pancreatic cancer patients using pimonidazole, but questions the reliability of measurements made using a single tissue section.

Hypoxia signaling and the metastatic phenotype

Conditions of poor oxygenation (hypoxia) are present in the majority of solid human tumors and are associated with poor patient prognosis due to both hypoxia-mediated resistance to treatment, and to hypoxia induced biological changes that promote increased malignancy, including metastasis. Tumor cells respond to hypoxia by activating several oxygen-sensitive signaling pathways that include the hypoxia inducible factor 1/2 (HIF1/2) signalling pathways and the unfolded protein response (UPR), which alter gene expression to promote adaptation and survival during hypoxic conditions. Furthermore, these hypoxia responsive pathways can lead to changes in gene expression and cellular phenotype that influence the potential of cancer cells to metastasize. However, the hypoxia-induced signaling events that promote tumor metastasis are still relatively poorly understood. Previous studies have largely focused on the contribution of the HIF signaling pathway to hypoxia-mediated metastasis. However, recent evidence demonstrates that hypoxic activation of the UPR is also an important mediator of metastasis.

Mitigation of radiation-induced lung injury with EUK-207 and genistein: effects in adolescent rats

Exposure of civilian populations to radiation due to accident, war or terrorist act is an increasing concern. The lung is one of the more radiosensitive organs that may be affected in people receiving partial-body irradiation and radiation injury in lung is thought to be associated with the development of a prolonged inflammatory response. Here we examined how effectively damage to the lung can be mitigated by administration of drugs initiated at different times after radiation exposure and examined response in adolescent animals for comparison with the young adult animals that we had studied previously. We studied the mitigation efficacy of the isoflavone genistein (50 mg/kg) and the salen-Mn superoxide dismutase-catalase mimetic EUK-207 (8 mg/kg), both of which have been reported to scavenge reactive oxygen species and reduce activity of the NFkB pathway. The drugs were given by subcutaneous injection to 6- to 7-week-old Fisher rats daily starting either immediately or 2 weeks after irradiation with 12 Gy to the whole thorax. The treatment was stopped at 28 weeks post irradiation and the animals were assessed for levels of inflammatory cytokines, activated macrophages, oxidative damage and fibrosis at 48 weeks post irradiation. We demonstrated that both genistein and EUK-207 delayed and suppressed the increased breathing rate associated with pneumonitis. These agents also reduced levels of oxidative damage (50-100%), levels of TGF-β1 expression (75-100%), activated macrophages (20-60%) and fibrosis (60-80%). The adolescent rats developed pneumonitis earlier following irradiation of the lung than did the adult rats leading to greater severe morbidity requiring euthanasia (∼37% in adolescents vs. ∼10% in young adults) but the extent of the mitigation of the damage was similar or slightly greater.

Mitigation of lung injury after accidental exposure to radiation

There is a serious need to develop effective mitigators against accidental radiation exposures. In radiation accidents, many people may receive nonuniform whole-body or partial-body irradiation. The lung is one of the more radiosensitive organs, demonstrating pneumonitis and fibrosis that are believed to develop at least partially because of radiation-induced chronic inflammation. Here we addressed the crucial questions of how damage to the lung can be mitigated and whether the response is affected by irradiation to the rest of the body. We examined the widely used dietary supplement genistein given at two dietary levels (750 or 3750 mg/kg) to Fischer rats irradiated with 12 Gy to the lung or 8 Gy to the lung + 4 Gy to the whole body excluding the head and tail (whole torso). We found that genistein had promising mitigating effects on oxidative damage, pneumonitis and fibrosis even at late times (36 weeks) when drug treatment was initiated 1 week after irradiation and stopped at 28 weeks postirradiation. The higher dose of genistein showed no greater beneficial effect. Combined lung and whole-torso irradiation caused more lung-related severe morbidity resulting in euthanasia of the animals than lung irradiation alone.

Characterization of image quality and image-guidance performance of a preclinical microirradiator

PURPOSE

To assess image quality and image-guidance capabilities of a cone-beam CT based small-animal image-guided irradiation unit (micro-IGRT).

METHODS

A micro-IGRT system has been developed in collaboration with the authors' laboratory as a means to study the radiobiological effects of conformal radiation dose distributions in small animals. The system, the X-Rad 225Cx, consists of a 225 kVp x-ray tube and a flat-panel amorphous silicon detector mounted on a rotational C-arm gantry and is capable of both fluoroscopic x-ray and cone-beam CT imaging, as well as image-guided placement of the radiation beams. Image quality (voxel noise, modulation transfer, CT number accuracy, and geometric accuracy characteristics) was assessed using water cylinder and micro-CT test phantoms. Image guidance was tested by analyzing the dose delivered to radiochromic films fixed to BB's through the end-to-end process of imaging, targeting the center of the BB, and irradiation of the film/BB in order to compare the offset between the center of the field and the center of the BB. Image quality and geometric studies were repeated over a 5-7 month period to assess stability.

RESULTS

CT numbers reported were found to be linear (R2 0.998) and the noise for images of homogeneous water phantom was 30 HU at imaging doses of approximately 1 cGy (to water). The presampled MTF at 50% and 10% reached 0.64 and 1.35 mm(-1), respectively. Targeting accuracy by means of film irradiations was shown to have a mean displacement error of [deltax, deltay, deltaz] = [-0.12, -0.05, -0.02] mm, with standard deviations of [0.02, 0.20, 0.17] mm. The system has proven to be stable over time, with both the image quality and image-guidance performance being reproducible for the duration of the studies.

CONCLUSIONS

The micro-IGRT unit provides soft-tissue imaging of small-animal anatomy at acceptable imaging doses (< or =1 cGy). The geometric accuracy and targeting systems permit dose placement with submillimeter accuracy and precision. The system has proven itself to be stable over 2 yr of routine laboratory use (>1800 irradiations) and provides a platform for the exploration of targeted radiation effects in small-animal models.

Dynamics of micronuclei in rat skin fibroblasts after X irradiation

In a previous study, we demonstrated DNA damage, expressed as micronuclei, in binucleate dermal fibroblasts obtained from human skin 2-9 weeks after fractionated radiotherapy. Here we assessed micronuclei in X-irradiated skin fibroblasts from 9-14-week-old female Lewis rats as a function of time after a single dose of radiation to determine the lifetime of such damage in the skin. After irradiation with 5, 10, 15 and 18 Gy, formation of micronuclei at 1 day or 2 months postirradiation increased up to about 10 Gy, with evidence for a plateau at higher doses. The time course of micronuclei present in the skin fibroblasts demonstrated a plateau region (approximately 20 days after 18 Gy and about 2 months after 10 Gy) before the number of micronuclei started to decline. Residual micronuclei were observed for more than 1 year after irradiation. Monomicronucleated cells predominated in fibroblasts from nonirradiated skin, whereas in fibroblasts from irradiated skin, multimicronucleated cells predominated and persisted (together with monomicronucleated cells) in the residual levels of damage at late times. The results suggest that DNA damage in dermal fibroblasts can be assayed by the micronucleus assay in samples from irradiated skin up to 1 month after irradiation for doses up to at least 10 Gy. Further studies are needed to define the dose-response relationship in detail.

Is there a relationship between repopulation and hypoxia/reoxygenation? Results from human carcinoma of the cervix

Long overall treatment times are detrimental for cure by radiotherapy and it has been argued that this may be due to repopulation occurring during the course of treatment. However, attempts to predict treatment outcome in relation to tumour proliferation, using pretreatment measurements of kinetic parameters such as Tpot or labelling index (LI) have not met with great success. One possible reason is that hypoxia/reoxygenation is linked to the growth of the tumour and its ability to repopulate. Data from studies in animal models have provided support for this possibility. We made measurement of tumour hypoxia, reoxygenation during treatment and pretreatment measurements of both Tpot and LI in groups of patients with cervix carcinoma undergoing radical radiation treatment. The data show a relationship between pretreatment pO2 measurements and treatment outcome, but reoxygenation did not show any association with treatment outcome. There was no significant association between pretreatment kinetic parameters and treatment outcome, nor was there any evidence of a relationship between pretreatment kinetic parameters and pO2. In the small group of 28 patients whose tumours underwent measurements of both pretreatment kinetic parameters (Tpot, LI) and reoxygenation, there was no relationship between these two sets of measurements. There was also no evidence that a combination of kinetic and reoxygenation measurements could be predictive of treatment outcome.

Cervix cancer regression measured using weekly MR imaging during fractionated radiotherapy: Radiobiologic modeling and correlation with tumor hypoxia

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Background: To utilize cervix cancer volumetry, as measured with MR imaging during definitive chemoirradiation (RT-CT), to derive radiobiological parameters using a mathematical model of tumor regression, and compare them to pre-treatment measurements of tumor hypoxia. Methods: Twenty-eight patients receiving RT-CT for cervix cancer underwent weekly magnetic resonance imaging (MRI) scans. Tumor volume was assessed on each of these scans and the rate of regression plotted. A mathematical model of tumor regression was formulated to simulate the relationship between three independent radiobiological parameters, 1) surviving fraction of cells after 2 Gy, SF2, 2) the cell clearance constant Tc, and 3) the cellular proliferation constant Tp. Non-linear regression analysis was applied to fit the MR-derived tumor volumes to the mathematical model and to derive SF2 and Tc values for each patient. These were compared to pre-treatment hypoxia measurements. Results: Initial tumor volume ranged between 8 and 209 cm3. Relative reduction in volume during treatment was 0.02 to 0.79. Simulations using representative values of the independent biologic variables derived from the literature showed SF2 and Tc to strongly influence the shape of the volume response curves. Non-linear regression analysis yielded a median SF2 of 0.71 and median Tc of 10 days. Radioresistant tumors (SF2 >0.71) were significantly more hypoxic at diagnosis (p=0.02). Conclusion: Based on serial MR imaging during treatment, a marked variation in cervix tumor regression is seen from patient to patient. Through our radiobiological model, tumors can be classified as radioresistant or radiosensitive, which correlates with hypoxia

[Table: see text]

No significant financial relationships to disclose.

Enhanced metastatic dissemination to multiple organs by melanoma and lymphoma cells in timp-3-/- mice

Identifying versatile inhibitors of metastasis that operate in multiple sites against distinct cancer cell types is important for designing novel therapeutics for metastasis. We show that multiple tissues of timp-3-/- mice are more susceptible to metastatic colonization. Overall, a 5-14-fold increase in liver and kidney colonization occurred by EL-4 lymphoma cells, and a twofold increase upon targeting B16F10 melanoma cells to the bone or lung of timp-3-/- mice. There was a general lack of macrophage or neutrophil localization to metastases in the liver, kidney and lung, and of osteoclasts to bone in both genotypes. Analysis of lung showed that proliferation or angiogenesis were unaltered within the metastatic colonies. Lung-trap assays revealed that initial tumor cell trapping was similar in the lung vasculature of timp-3-/- and wild-type mice. However, more tumor cells were found in timp-3-/- lungs at 48 and 96 h after tumor cell injection indicating more efficient extravasation and initial proliferation. Activation of pro-MMP-2 was greater in timp-3-/- lungs at these time points. These data demonstrate TIMP-3 functions to inhibit metastatic dissemination of diverse cancer cells to multiple organs. TIMP-3 regulates MMP-2 activation to limit tumor cell extravasation and subsequent colonization of the lung, without augmenting inflammatory cell response.

Melanocyte stimulating hormone peptides inhibit TNF-alpha signaling in human dermal fibroblast cells

Alpha-melanocyte stimulating hormone (alpha-MSH) has been identified as a potent anti-inflammatory in various tissues including the skin. It has previously been shown in skin cell keratinocytes and melanocytes/melanoma cells that MSH peptides inhibit TNF-alpha stimulated NF-kappaB activity and intercellular adhesion molecule-1 (ICAM-1) upregulation. However, the precise anti-inflammatory role of MSH peptides in dermal fibroblasts is unclear. Some studies report on pro-inflammatory responses, while others on anti-inflammatory responses. The present study confirms MC1R expression in cultured human dermal fibroblasts and reports that the MSH peptides alpha-MSH and KP(-D-)V inhibit TNF-alpha stimulated NF-kappaB activity and ICAM-1 upregulation, consistent with an anti-inflammatory role. However, involvement of IkappaB-alpha regulation by either peptide was not confirmed, supporting a mechanism independent of the NF-kappaB inhibitor. In conclusion, alpha-MSH and KP(-D-)V peptides have an anti-inflammatory action on dermal fibroblast signaling by inhibiting the pro-inflammatory activity of TNF-alpha in vitro.

Effects of tumour acidification with glucose+MIBG on the spontaneous metastatic potential of two murine cell lines

In addition to hypoxia, acidic extracellular pH (pH_e) is recognised as one of the microenvironmental characteristics of solid tumours. A number of studies have examined ways to increase tumour acidity in order to improve tumour-specific targeting of certain drugs and the effectiveness of hyperthermia. However, previous data have shown that exposure of murine tumour cells to acid conditions in culture can enhance their metastatic potential when injected subsequently into mice, raising the concern that deliberate tumour acidification might increase the probability of metastasis. In this study, we examined the effects of in vivo tumour acidification and hypoxia on the spontaneous metastatic potential of the murine KHT-C fibrosarcoma and B16F1 melanoma cell lines. A tumour-specific increase in extracellular acidity, demonstrated by measurements with pH electrodes, was achieved by daily intraperitoneal injections of meta-iodo-benzylguanidine (MIBG) and/or glucose. This method of tumour acidification during tumour growth did not significantly enhance the spontaneous metastatic potential of the two murine cell lines.

Measurement of NF-kappaB in normal and reconstructed human skin in vitro

The survival of grafted donor skin for the treatment of burn injuries depends on several factors including wound bed vascularisation and the intensity of acute inflammation shortly after injury. However, acceptance rates approximate 50% at best and therefore a clinical need exists for improvement. The aim of the study was to develop a method for assessing the inflammatory response of cells in skin tissue based on activation of the NF-kappa B (NF-kappaB) transcription factor complex, thereby providing a basis for analysing the inflammatory component and anti-inflammatory strategies for tissue-engineered treatments. We have extended a standard method of measuring NF-kappaB in monolayer cultures that relies on determining translocation of the p65 subunit from the cytoplasm to the nucleus. Normal human skin and tissue engineered skin was analysed using an immunofluorescence microscopy technique, that revealed base line NF-kappaB activation in the epidermis and dermis were different. It was possible to determine the activation of NF-kappaB in skin tissue, enabling correlation that NF-kappaB measurement is a sensitive indicator of cellular responses in 3-D tissue. The approach will provide a basis for early responses of skin cells in determining the efficacy of anti-inflammatory delivery via tissue-engineered scaffolds for burn injuries.

Molecular mechanisms of tumor invasion and metastasis: an integrated view

As tumors progress to increased malignancy, cells within them develop the ability to invade into surrounding normal tissues and through tissue boundaries to form new growths (metastases) at sites distinct from the primary tumor. The molecular mechanisms involved in this process are incompletely understood but those associated with cell-cell and cell-matrix adhesion, with the degradation of extracellular matrix, and with the initiation and maintenance of early growth at the new site are generally accepted to be critical. This article discusses current knowledge of molecular events involved in these various processes. The potential role of adhesion molecules (eg. integrins and cadherins) has undergone a major transition over the last ten years, as it has become apparent that such molecules play a major role in signaling from outside to inside a cell, thereby controlling how a cell is able (or not) to sense and interact with its local environment. Similarly the roles of proteolytic enzymes and their inhibitors (eg. matrix metalloproteinases and TIMPs) have also expanded as it has become apparent that they not only have the abilities to break down the components of the extracellular matrix but also are involved in the release of factors which can affect the growth of the tumor cells positively or negatively. Recent work has highlighted the importance of the later, post-extravasational stages of metastasis, where adhesion and proteolysis are now known to play a role along with other processes such as apoptosis, dormancy, growth factor-receptor interactions and signal transduction. Recent work has also demonstrated that not only the immediate cellular microenvironment, in terms of specific cell-cell and cell-matrix interactions, but also the extended cellular microenvironment, in terms of vascular insufficiency and hypoxia in the primary tumor, can modify cellular gene expression and enhance metastasis. Mechanisms of metastasis appear to involve a complex array of genetic and epigenetic changes many of which appear to be specific both for different types of tumors and for different sites of metastasis. Our improved understanding of the expanded roles of the individual molecules involved has resulted in a mechanistic blurring of the previously described discrete stages of the metastatic process.

pH, hypoxia and metastasis

The vascular supply to tumours is often poorly formed and irregular with the result that tumours may contain regions of poor nutritional supply with hypoxia and acidic pH. Clinical studies have demonstrated substantial heterogeneity in oxygenation in human tumours. In some studies tumours with poorer oxygenation were more likely to have metastasized. In our studies of carcinoma of the cervix, nodal metastases were 1.5 times more likely at diagnosis in patients with more hypoxic tumours relative to those with less hypoxic tumours. Transplanted rodent KHT fibrosarcomas and SCC-VII squamous cell tumours also have variability in levels of oxygenation; again, the more hypoxic tumours are found to be more metastatic. Furthermore, deliberate exposure of KHT tumours to cyclic hypoxia (12 cycles of 5% oxygen breathing for 10 min interspersed with 10 min air breathing) every day during their growth, doubled the level of micrometastases that were detected in the lungs of the mice. These findings are consistent with in vitro studies demonstrating that KHT and SCC-VII cells and B-16 melanoma cells exposed to hypoxia or low pH have increased propensity to form metastases following injection into-mice. This effect is transient and is lost within about 48 h of removal of exposure to hypoxia or low pH, suggesting that the effect may be due to changes in gene expression associated with that stress. Recent studies have implicated a number of genes, such as vascular endothelial growth factor and interleukin 8, in the effect of hypoxic and acid pH on metastasis.

Tumor hypoxia has independent predictor impact only in patients with node-negative cervix cancer

PURPOSE

This prospective clinical study was begun in 1994 to validate the independent prognostic impact of tumor hypoxia in patients with cervix cancer treated with definitive radiation therapy.

PATIENTS AND METHODS

Between May 1994 and January 1999, 106 eligible patients with epithelial cervix cancer had tumor oxygen pressure (PO(2)) measured using the Eppendorf probe. Oxygenation data are presented as the hypoxic proportion, defined as the percentage of PO(2) readings less than 5 mm/Hg (abbreviated as HP(5)) and the median PO(2).

RESULTS

The median HP(5) in individual patients was 48%, and the median PO(2) was HP(5). Progression-free survival (PFS) for patients with hypoxic tumors (HP(5) > 50%) was 37% at 3 years versus 67% in those patients with better oxygenated tumors (P =.004). In multivariate analysis, only tumor size (risk ratio [RR], 1.33; P =.0003) and evidence of pelvic nodal metastases on imaging studies (RR, 2.52; P =.0065) were predictive of PFS. However, an interaction between nodal status and oxygenation was observed (P =.006), and further analysis indicated that HP(5) was an independent predictor of outcome in patients with negative nodes on imaging (P =.007). There was a significant increase in the 3-year cumulative incidence of distant metastases in the hypoxic group (41% v 15% in those with HP(5) < 50%; P =.0023), but not in pelvic relapse (37% v 27%; P =.12).

CONCLUSION

Tumor hypoxia is an independent predictor of poor PFS only in patients with node-negative cervix cancer, in addition to tumor size. Its impact appears to be related to an increased risk of distant metastases rather than to an effect on pelvic control.

Acute (cyclic) hypoxia enhances spontaneous metastasis of KHT murine tumors

Hypoxia exists in most human and rodent solid tumors and has been shown to correlate with poor survival in carcinoma of the cervix, carcinoma of the head and neck, and soft tissue sarcoma. It exists both chronically, due to the poorly organized vasculature of solid tumors, and acutely, due to fluctuations in blood flow. It has been found that tumors that are more hypoxic are more likely to metastasize in humans and in rodent models, and it has been demonstrated that exposure of tumor cells to hypoxia in vitro can transiently enhance their metastatic potential when they are reinjected i.v. into mice. The purpose of the present study was to determine whether experimentally imposed hypoxic stress in vivo, either chronic or acute, affects the process of spontaneous metastasis in tumor-bearing mice. We exposed mice bearing KHT tumors to low oxygen conditions (5-7% O(2) breathing) daily during tumor growth in an attempt to induce additional chronic (2 h/day) and acute (12 x 10 min/day) hypoxia in their tumors. By monitoring tumor pO(2) levels over the course of treatment, we demonstrated that these treatments produce acute and chronic hypoxia within the tumor tissue. The acute but not the chronic hypoxia treatment significantly increased the number of spontaneous microscopic lung metastases in the mice by a factor of about 2, and the results suggest that this effect was due to the changes induced in the primary tumor. This study describes a novel method for studying the effects of hypoxia in solid tumors and demonstrates that acute and chronic hypoxia can have different effects on tumor cell behavior in vivo.

Relationship of hypoxia to metastatic ability in rodent tumours

The relationship between tumour oxygenation in vivo and metastatic potential was investigated in 2 rodent tumour models, KHT-C fibrosarcoma and SCC-VII squamous cell carcinoma. The oxygen status in these rodent tumours transplanted intramuscularly in syngeneic mice was measured using the Eppendorf pO(2)Histograph. The results indicate a considerable heterogeneity in oxygenation between individual tumours within each tumour cell line. At different tumour sizes, animals were killed and lung lobes were examined for macroscopic and microscopic lung metastases. In the KHT-C tumours, a significant increase in early pulmonary metastasis formation was observed in mice with hypoxic primary tumours. Hypoxic SCC-VII tumours did not give rise to enhanced lung metastasis formation despite oxygenation in a range similar to the KHT-C tumours. However, the overall metastasis incidence in the SCC-VII model was very low. The results obtained in the KHT-C model, which show that hypoxic tumours are more likely to metastasize, are in agreement with recent clinical data suggesting that a hypoxic environment might be implicated in metastatic ability of human tumours.

Normal tissue radiobiology: from the laboratory to the clinic

This manuscript is in four parts, presenting the four talks given in a symposium on normal tissue radiobiology. The first part addresses the general concept of the role of parenchymal cell radiosensitivity vs. other factors, highlighting research over the last decade that has altered our understanding of factors underlying normal tissue response. The other three parts expand on specific themes raised in the first part dealing in particular with (1) modifications of fibroblast response to irradiation in relation to the induction of tissue fibrosis, (2) the use of the linear-quadratic equation to model the potential benefits of using different means (both physical and biologic) of modifying normal tissue response, and (3) the specific role of the growth factor TFG-beta1 in normal tissue response to irradiation. The symposium highlights the complexities of the radiobiology of late normal tissue responses, yet provides evidence and ideas about how the clinical problem of such responses may be modified or alleviated.

In-field and out-of-field effects in partial volume lung irradiation in rodents: possible correlation between early dna damage and functional endpoints

PURPOSE

Recent observations have shown that there are regional variations in radiation response in mouse lung as measured by functional assays. Furthermore, there are both in-field and out-of-field effects in radiation-induced lung damage as observed by DNA assay in rats. The purpose of this work is: (a) to examine mice lethality data following partial volume lung irradiation to assess the possibility of directional or regional effects, (b) to evaluate the correlation between mice lethality data and DNA damage assayed by micronuclei production in rat lung, and (c) to re-interpret mice lethality considering the existence of directional effects in lung cellular response to partial volume irradiation.

METHODS AND MATERIALS

The lethality data for mice, generated at the M. D. Anderson Cancer Center, Houston, and micronuclei yield data for rats obtained at Princess Margaret Hospital, Toronto, were used. A radiobiological model that allows for out-of-field and in-field effects for lung cell damage and lung response was developed. This model is based on the observation of DNA damage in shielded parts of rat lung that was assumed relevant to cell lethality and consequently overall lung response.

RESULTS

While the experimental data indicated directional or regional volume effects, the applicability of dose and volume as sole predictors of lung response to radiation was found to be unreliable for lower lung (base) irradiation in mice. This conforms well to rat lung response where micronuclei were observed in shielded apical parts of lung following base irradiation. The radiobiological model, which was specifically developed to account for the lung response outside of primary irradiated volume, provides a good fit to mice lethality data, using parameters inferred from rat micronuclei data.

CONCLUSION

Response to lung irradiation in rodents, in particular, elevated sensitivity to base irradiation, can be interpreted with a hypothesis of in-field and out-of-field effects for cellular response. If the existence of these effects for lung is subsequently proven in humans, it will require the incorporation of geometrical and directional information in normal tissue complication probability calculations for lung. These considerations are ignored in present approaches based only on conventional dose-volume histograms.

Anemia, hypoxia and transfusion in patients with cervix cancer: a review

BACKGROUND AND PURPOSE

With the recent development of hemopoietic growth factors and alternatives to transfusion, there has been a renewed interest in the relationships between anemia, tumor hypoxia and treatment outcome in a number of human malignancies. This review is intended to provoke a reconsideration of these issues and their effect on clinical trials, aimed at improving treatment outcome in patients with cervix cancer.

MATERIALS AND METHODS

Using data from the literature and from our own prospective series of tumor oxygenation in cervix cancer, we modeled the impact of anemia on tumor blood flow and hypoxia in animal models and human tumors, examined the relationship between anemia and hypoxia and treatment outcome in patients, and reviewed the impact of transfusion on tumor hypoxia and treatment outcome in cervix cancer.

RESULTS

Anemia may result in a significant reduction in oxygen delivery to tumors, but compensatory mechanisms reduce the impact on tumor oxygenation. Anemia is associated with inferior treatment outcome in cervix cancer, but hemoglobin levels prior to and during treatment are strongly correlated with tumor size, and this may explain the prognostic impact of anemia in older studies. Transfusion and erythropoietin ameliorate hypoxia in only a proportion of anemic patients. Critical analysis of the published data from the Princess Margaret Hospital randomized trial of transfusion in cervix cancer reveals that, when analyzed by intention-to-treat, transfusion did not result in a benefit to patients.

CONCLUSIONS

This review suggests that the relationships among anemia, hypoxia, transfusion and treatment outcome are complex. Further study of anemia as an independent prognostic factor is required and randomized studies of transfusion alternatives, such as erythropoietin, must be of sufficient size to detect small treatment effects.

Cost-effectiveness of prophylactic antiemetic therapy with ondansetron, droperidol, or placebo

BACKGROUND

In an era of growing economic constraints on healthcare delivery, anesthesiologists are increasingly expected to understand cost analysis and evaluate clinical practices. Postoperative nausea and vomiting (PONV) are distressing for patients and may increase costs in an ambulatory surgical unit. The authors compared the cost-effectiveness of four prophylactic intravenous regimens for PONV: 4 mg ondansetron, 0.625 mg droperidol, 1.25 mg droperidol, and placebo.

METHODS

Adult surgical outpatients at high risk for PONV were studied. Study drugs were administered intravenously within 20 min of induction of nitrous oxide-isoflurane or enflurane anesthesia. A decision-tree analysis was used to group patients into 12 mutually exclusive subgroups based on treatment and outcome. Costs were calculated for the prevention and treatment of PONV. Cost-effectiveness analysis was performed for each group.

RESULTS

Two thousand sixty-one patients were enrolled. Efficacy data for study drugs have been previously reported, and the database from that study was used for pharmacoeconomic analysis. The mean-median total cost per patient who received prophylactic treatment with 4 mg ondansetron, 0.625 mg droperidol, 1.25 mg droperidol, and placebo were $112 or $16.44, $109 or $0.63, $104 or $0.51, and $164 or $51.20, respectively (P = 0.001, active treatment groups vs. placebo). The use of a prophylactic antiemetic agent significantly increased patient satisfaction (P < 0.05). Personnel costs in managing PONV and unexpected hospital admission constitute major cost components in our analysis. Exclusion of nursing labor costs from the calculation did not alter the overall conclusions regarding the relative costs of antiemetic therapy.

CONCLUSION

The use of prophylactic antiemetic therapy in high-risk ambulatory surgical patients was more effective in preventing PONV and achieved greater patient satisfaction at a lower cost compared with placebo. The use of 1.25 mg droperidol intravenously was associated with greater effectiveness, lower costs, and similar patient satisfaction compared with 0.625 mg droperidol intravenously and 4 mg ondansetron intravenously.

111In-labeled EGF is selectively radiotoxic to human breast cancer cells overexpressing EGFR

Our objective was to determine whether the internalization and nuclear translocation of human epidermal growth factor (hEGF) after binding to its cell surface receptor (EGFR) could be exploited to deliver the Auger electron emitter 111In into EGFR-positive breast cancer cells for targeted radiotherapy.

METHODS

hEGF was derivatized with diethylenetriamine pentaacetic acid (DTPA) and radiolabeled with 111In-acetate. The internalization of 111In-DTPA-hEGF by MDA-MB-468 breast cancer cells (1.3x10(6) EGFRs/cell) was determined by displacement of surface-bound radioactivity by an acid wash. The radioactivity in the cell nucleus and chromatin, isolated by differential centrifugation, was measured. The effect on the growth rate of MDA-MB-468 or MCF-7 (1.5x10(4) EGFRs/cell) cells was determined after treatment in vitro with 111In-DTPA-hEGF, unlabeled DTPA-hEGF, or 111In-DTPA. The surviving fraction of MDA-MB-468 or MCF-7 cells treated in vitro with 111In-DTPA-hEGF was determined in a clonogenic assay. The radiotoxicity in vivo against normal hepatocytes or renal tubular cells was evaluated by measuring alanine aminotransferase (ALT) or creatinine levels in mice administered high amounts of 111In-DTPA-hEGF (equivalent to human doses up to 14,208 MBq) and by light and electron microscopy of the tissues.

RESULTS

Approximately 70% of 111In-DTPA-hEGF was internalized by MDA-MB-468 cells within 15 min at 37 degrees C and up to 15% was translocated to the nucleus within 24 h. Chromatin contained 10% of internalized radioactivity. The growth rate of MDA-MB-468 cells was decreased 3-fold by treatment with 111In-DTPA-hEGF (45-60 mBq/cell). Treatment with unlabeled DTPA-hEGF caused a 1.5-fold decrease in growth rate, whereas treatment with 111In-DTPA had no effect. Targeting of MDA-MB-468 cells with up to 130 mBq/cell of 111In-DTPA-hEGF resulted in a 2-logarithm decrease in their surviving fraction. No decrease in the growth rate or surviving fraction of MCF-7 cells was evident. There was no evidence of hepatotoxicity or renal toxicity in mice administered high amounts of 111In-DTPA-hEGF. Radiation dosimetry estimates suggest that the radiation dose to an MDA-MB-468 cell targeted with 111In-DTPA-hEGF could be as high as 25 Gy with up to 19 Gy delivered to the cell nucleus.

CONCLUSION

111In-DTPA-hEGF is a promising novel radiopharmaceutical for targeted Auger electron radiotherapy of advanced, hormone-resistant breast cancer.

The use of needle biopsies for radiobiological assessment of oxygen levels in KHT-C tumors

Hypoxia affects the sensitivity of cells to radiation. Hence there is considerable interest in the development and assessment of techniques for measuring oxygen levels. In the work described here, we explore the use of tumor needle biopsies (fine needle aspirates) in an assay that is standard in the field of radiation biology: the paired survival assay. We found that needle biopsies are a feasible option for estimating cell survival when conducting this assay, and that the variability in cell survival between tumors was greater than that between different biopsies from the same tumor. Using this technique, we then compared measurements of tumor hypoxia using the paired survival assay and the growth delay assay in the same individual tumors. We found a significant correlation between these two techniques.

Intradermal injection of autologous dermal fibroblasts improves wound healing in irradiated skin

BACKGROUND

Despite its well-recognized benefits in the management of several solid tumors, the use of radiotherapy prior to surgery is associated with a high incidence of significant surgical wound healing complications. Radiation-induced damage to dermal fibroblasts has been proposed as an important cause. We hypothesized that the introduction of normal, unirradiated fibroblasts into previously irradiated skin would enhance healing of the subsequent surgical wound.

MATERIALS AND METHODS

Four groups of wounds were examined in female Wistar rats: (1) unirradiated skin (n = 10), (2) irradiated skin injected with tissue culture medium alone (n = 17), (3) irradiated skin injected with autologous dermal fibroblasts (n = 17), and (4) irradiated skin injected with irradiated autologous dermal fibroblasts (n = 7). Wounds were evaluated biomechanically and histologically.

RESULTS

The biomechanical values of breaking load, ultimate tensile strength, elastic modulus, and toughness were significantly greater in the irradiated wounds injected with fibroblasts than those injected with medium only. These cell-injected wounds did not perform as well biomechanically as those in unirradiated skin. Irradiating the cells prior to injection resulted in biomechanical results no better than those in medium-injected wounds.

CONCLUSIONS

These results demonstrate that injection of normal, unirradiated fibroblasts significantly improves healing of the irradiated surgical wound. These cells are likely better able to respond to the proliferative, migratory, and synthetic demands of the wound healing environment, as injection of irradiated cells has an equivalent effect on healing as injection of medium alone.

Gene expression in individual cells: analysis using global single cell reverse transcription polymerase chain reaction (GSC RT-PCR)

The determination of the gene expression pattern of single cells has important implications for many areas of cellular and developmental biology including lineage determination, identification of primitive stem cells and temporal gene expression patterns induced by changes in the cellular microenvironment. Global Single Cell Reverse Transcription-Polymerase Chain Reaction (GSC RT-PCR) enables the study of single cell gene expression patterns. Initial observations of significant heterogeneity among single cells derived from a population of cells prompted us to determine how much of this observed heterogeneity was due to the intrinsic variation within the method. In this paper we discuss the sensitivity of GSC RT-PCR for analysis of differences in gene expression between single cells and, in particular, detail the amount of variation generated by the method itself. We found that most of the intrinsic variation in the method occurred in the PCR step. The total variation induced by the method was in the range of 5 fold. While we have determined that there is a five fold methodological variation in GSC RT-PCR, any method which use its components (including generation of cDNAs for microarray analysis) is likely to be affected by such experimental variability, which could limit the interpretation of the resulting data.

A comparison in individual murine tumors of techniques for measuring oxygen levels

PURPOSE

To investigate the relationship between different techniques for measuring oxygen levels in a murine tumor model.

METHODS AND MATERIALS

Using the murine fibrosarcoma line KHT-C, five techniques of measuring oxygen levels-the Eppendorf pO2 Histograph, EF5 binding, the comet assay, a paired survival assay, and an in vivo growth delay assay-were assessed. In these experiments, three or more techniques were applied in different combinations to measure the oxygen levels in individual tumors.

RESULTS

Statistically significant correlations were observed between the hypoxic proportions calculated from the paired survival assay with those from EF5 binding. The comet assay was found to have a statistically significant correlation with the paired survival analysis and the growth delay analysis. No statistically significant correlation was found between the Eppendorf pO2 Histograph measurements and those from the other techniques, although there were weak correlations with the paired survival assay and EF5 binding. For technical reasons, a comparison was not made between EF5 binding and the growth delay assay.

CONCLUSIONS

The correlations found between EF5 binding and the comet assay with the radiobiological assays suggest that these techniques have potential for predicting outcome following radiation treatment. The lack of correlation seen between the pO2 Histograph data and the radiobiological assays is in contrast to results from early clinical trials.

A quantitative analysis of the reduction in oxygen levels required to induce up-regulation of vascular endothelial growth factor (VEGF) mRNA in cervical cancer cell lines

The presence of hypoxia (low oxygen concentrations) in solid tumours correlates with poor prognosis, increased metastasis, and resistance to radiotherapy and some forms of chemotherapy. Malignant cells produce an angiogenesis factor, vascular endothelial growth factor (VEGF), which may increase metastatic ability and is up-regulated in the presence of hypoxia. Clinical data for cancers of the cervix and head and neck relate oxygen levels in the tumour to treatment outcome. This suggests the possibility that the presence of VEGF mRNA might be used as a marker for relevant levels of hypoxia. Suspension cultures of three human cervical cancer cell lines, SiHa, ME-180 and HeLa, were used to investigate up-regulation of VEGF mRNA levels following exposure to precisely defined oxygen concentrations for 2 or 4 h. An oxygen sensor was used to confirm the actual levels of dissolved oxygen present. The oxygen concentrations which caused half-maximal upregulation (the Km value) of VEGF mRNA level in the three cell lines were similar except for one instance (Km at 4 h: SiHa 27.0 +/- 5.7 microM, ME-180 16.8 +/- 3.3 microM, HeLa 13.0 +/- 1.8 microM, SiHa and HeLa P = 0.01). The Km values for the HeLa cell line as measured at 2 h (24.9 +/- 0.8 microM) and 4 h (13.0 +/- 1.8 microM) were significantly different (P < 0.0001). VEGF mRNA half-lives measured in air were consistent with values in the literature (SiHa 59.8 +/- 5.8 min, ME-180 44.4 +/- 7.2 min, HeLa 44.5 +/- 6.3 min). Differences in oxygen consumption at low oxygen concentrations were noted between the different cell lines. Stirring in suspension culture was found to induce VEGF mRNA in SiHa cells. The presence of VEGF mRNA may be a marker for radiobiologic hypoxia.

The relationship between elevated interstitial fluid pressure and blood flow in tumors: a bioengineering analysis

PURPOSE

To examine the hypothesis that elevated interstitial fluid pressure (IFP) is a cause of reduced blood flow in tumors.

MATERIALS AND METHODS

A physiologic model of tumor blood flow was developed based on a semipermeable, compliant capillary in the center of a spherical tumor. The model incorporates the interaction between the tumor vasculature and the interstitium, as mediated by IFP. It also incorporates the dynamic behavior of the capillary wall in response to changes in transmural pressure, and the effect of viscosity on blood flow.

RESULTS

The model predicted elevated tumor IFP in the range of 0 to 56 mmHg. The capillary diameter in the setting of elevated IFP was greatest at the arterial end, and constricted to between 3.2 and 4.4 microm at the venous end. This corresponded to a 2.4- to 3.5-fold reduction in diameter along the length of the capillary. The IFP exceeded the intravascular pressure distally in the capillary, but vascular collapse did not occur. Capillary diameter constriction resulted in a 2.3- to 9.1-fold steady-state reduction in tumor blood flow relative to a state of near-zero IFP.

CONCLUSION

The results suggest that steady-state vascular constriction occurs in the setting of elevated IFP, and leads to reduced tumor blood flow. This may in turn contribute to the development of hypoxia, which is an important cause of radiation treatment failure in many tumors.

Analysis of genomic integrity and p53-dependent G1 checkpoint in telomerase-induced extended-life-span human fibroblasts

Life span determination in normal human cells may be regulated by nucleoprotein structures called telomeres, the physical ends of eukaryotic chromosomes. Telomeres have been shown to be essential for chromosome stability and function and to shorten with each cell division in normal human cells in culture and with age in vivo. Reversal of telomere shortening by the forced expression of telomerase in normal cells has been shown to elongate telomeres and extend the replicative life span (H. Vaziri and S. Benchimol, Curr. Biol. 8:279-282, 1998; A. G. Bodnar et al., Science 279:349-352, 1998). Extension of the life span as a consequence of the functional inactivation of p53 is frequently associated with loss of genomic stability. Analysis of telomerase-induced extended-life-span fibroblast (TIELF) cells by G banding and spectral karyotyping indicated that forced extension of the life span by telomerase led to the transient formation of aberrant structures, which were subsequently resolved in higher passages. However, the p53-dependent G1 checkpoint was intact as assessed by functional activation of p53 protein in response to ionizing radiation and subsequent p53-mediated induction of p21(Waf1/Cip1/Sdi1). TIELF cells were not tumorigenic and had a normal DNA strand break rejoining activity and normal radiosensitivity in response to ionizing radiation.

Cervix cancer oxygenation measured following external radiation therapy

PURPOSE

Tumor hypoxia may be an important factor predicting relapse following radiation therapy. This study was designed to determine the relationship between the oxygenation parameters measured using a polarographic oxygen electrode, prior to and during treatment in patients with cervix cancer, and to assess these results with regard to patient survival.

MATERIALS AND METHODS

Forty-three patients had pretreatment oxygen assays performed and measurements repeated following external beam radiation to a median dose of 50 Gy (range 26-52 Gy). Stage distribution showed 15 patients in Stage IB, 17 in Stage II, and 11 in Stage III. The median tumor size was 5 cm (range 3-10 cm).

RESULTS

The median proportion of pO2 values <5 mm Hg (the HP5) was 41% following radiation, and the median pO2 was 12 mm Hg. These results were not significantly different from the pretreatment HP5 or pO2 of 37% and 12 mm Hg, respectively. Disease-free survival at 2 years was 50% in patients with posttreatment HP5 < or =50%, compared to 60% when posttreatment HP5 was >50% (p = 0.35).

CONCLUSIONS

Unlike pretreatment results, tumour oxygenation measured following external radiation does not appear to be a useful predictive assay in patients with cervical cancer.

Effect of simultaneous pulsed hyperthermia and pulsed radiation treatment on survival of SiHa cells

Relatively mild temperatures (40-41.5 degrees C) can sensitize human cells to radiation without the development of thermal tolerance to radiosensitization. Therefore there may be a therapeutic benefit to adding mild hyperthermia to brachytherapy regimens for the treatment of cancer. However, the required heating times are long (approximately 48 h) which renders this approach somewhat impractical. A novel alternative is to combine pulsed brachytherapy with pulsed hyperthermia to enable the total radiation dose to be given at an elevated temperature while the total heating time is kept short. A treatment schedule in which 1 Gy radiation pulses were given once per hour during 5-min heating pulses also delivered once per hour, was investigated in vitro in the human cervical carcinoma line, SiHa. The degree of cytotoxicity and thermoradiosensitization of the cells were assessed by cell survival using the colony forming assay. Cells were exposed to pulsed hyperthermia alone (5 min at 45 degrees C, delivered once per hour), acute hyperthermia alone (45 degrees C), pulsed radiation alone (1 Gy per hour), acute radiation alone, and simultaneous pulsed hyperthermia and pulsed radiation. Pulsed heating alone caused little cytotoxicity. However when pulsed heating was added to pulsed radiation, the level of cytotoxicity was greater than for pulsed radiation alone or acute radiation alone. The effect was also greater than would be predicted from a simple additive effect of pulsed radiation and pulsed heating. In conclusion, pulsed heating at 45 degrees C sensitized cells to pulsed radiation without the development of thermal tolerance.

Heterogeneity of tumor oxygenation: relationship to tumor necrosis, tumor size, and metastasis

PURPOSE

Measurements of oxygenation in the transplanted rodent KHT-C and SCC-VII tumors demonstrate significant heterogeneity from tumor to tumor as is observed in human tumors. This finding suggests that heterogeneity in oxygenation between tumors is likely related to factors associated with tumor growth rather than to intrinsic genetic differences. In this study we examined whether measurements of the oxygenation of individual KHT-C tumors were related to necrosis in the tumors or to tumor size and whether the more hypoxic tumors gave rise to more metastases.

METHODS

Tumors were grown in the gastrocnemius muscle of C3H mice and tumor oxygenation was measured at defined sizes (approx. 0.35 g, 1.0 g, and 2.0 g) using an Eppendorf polarographic oxygen probe. Necrosis was assessed by examining histological sections cut from tumors used for the oxygen measurements. Metastasis was assessed by counting macroscopic lung nodules in mice sacrificed when their tumors reached a size of approximately 2 g.

RESULTS

Tumor oxygenation in individual KHT-C tumors became poorer and necrosis became more extensive as the tumors grew larger but, at a size of 0.3-0.4 g, there was no relationship between oxygenation and extent of necrosis. In general, measurements of tumor pO2 at a size of 0.3-0.4 g were predictive of tumor PO2 in the same tumor at a size of about 1 g, but by the time the tumors reached a size of about 2 g they were all very hypoxic. There was a trend suggesting a relationship between macroscopic metastases in the lung and degree of hypoxia in the KHT-C tumors but this was not statistically significant.

CONCLUSION

The results indicate that the heterogeneity of oxygenation seen in KHT-C tumors is not explained by different degrees of necrosis in the individual tumors. The lack of a correlation between increased metastasis formation and increased levels of hypoxia in the KHT-C tumors is not consistent with results reported for human tumors.

Oxygenation predicts radiation response and survival in patients with cervix cancer

BACKGROUND AND PURPOSE

Hypoxia appears to be an important factor in predicting tumor relapse following radiation therapy. This study measured oxygenation prior to treatment in patients with cervix cancer using a polarographic oxygen electrode to determine if oxygenation was an important prognostic factor with regard to tumor control and survival.

MATERIALS AND METHODS

Between May 1994 and June 1997, 74 eligible patients with cervix cancer were entered into an ongoing prospective study of tumor oxygenation prior to primary radiation therapy. All patients were evaluated with an Eppendorf oxygen electrode during examination under anesthesia. Oxygenation data are presented as the hypoxic proportion, defined as the percentage of pO2 readings of <5 mm Hg (abbreviated as HP5).

RESULTS

The HP5 ranged from 2 to 99% with a median of 52%. With a median follow-up of 1.2 years, the disease-free survival (DFS) rate was 69% for patients with HP5 of < or =50% compared with 34% for those with HP5 of >50% (log-rank P = 0.02). Tumor size above and below the median of 5 cm was also significantly related to DFS (P = 0.0003) and patients with bulky hypoxic tumors had a significantly lower DFS (12% at 2 years) than either bulky oxygenated or non-bulky oxygenated or hypoxic tumors (65%, P = 0.0001).

CONCLUSIONS

Hypoxia and tumor size are significant adverse prognostic factors in a univariate analysis of disease-free survival in patients with cervix cancer. A high risk group of patients with bulky hypoxic tumors have a significantly higher probability of relapse and death.

Interstitial fluid pressure in cervical carcinoma: within tumor heterogeneity, and relation to oxygen tension

BACKGROUND

Interstitial fluid pressure (IFP) is elevated in many animal and human tumors. The authors assessed tumor IFP and its relation to tumor oxygenation in a prospective clinical study of patients with cervical carcinoma.

METHODS

Measurements were made in 77 patients with cervical carcinoma prior to treatment. IFP was measured in normal paravaginal submucosal tissue and at one to five positions in the visible tumor with the patients anesthetized and in the lithotomy position. Tumor oxygen tension was measured immediately prior to IFP using a polarographic needle electrode. Patients were treated with radiotherapy only. Response was evaluated 3 months after the completion of radiotherapy.

RESULTS

There was substantial variation in IFP from region to region in some tumors. The mean IFP in individual tumors ranged from 3 to 48 millimeters of mercury (mmHg). The overall mean and median values for the entire patient group were 19 mmHg and 17 mmHg, respectively. IFP was significantly higher in tumor tissue than in normal tissue (P < 0.0001). Tumors with high IFP were more likely to be hypoxic (P < 0.007) and less likely to regress completely with radiotherapy (P < 0.04).

CONCLUSIONS

IFP in cervical carcinoma is elevated above normal tissue values. Multiple measurements are needed to evaluate IFP in these tumors. High IFP is associated with hypoxia and may provide information about the mechanism of hypoxia on which treatment can be based.

Partial volume rat lung irradiation: an evaluation of early DNA damage

PURPOSE

1. To investigate early DNA damage induced in rat lung cells following single-dose, partial-volume irradiation (lung base and lung apex). 2. To determine the variation in DNA damage in different lung regions. 3. To investigate the possible mechanisms associated with early DNA damage after lung irradiation.

METHODS AND MATERIALS

The whole lung or the upper or lower half of the entire lung of Sprague-Dawley rats was exposed to 10 Gy 60Co gamma rays. The animals were sacrificed at various times up to 42 h after irradiation. A trypsin-digested lung cell suspension was prepared and cells that attached to slides in the initial 24-h period were then grown in the presence of culture medium with cytochalasin-B for a further 72 h. Radiation-induced DNA damage was quantified in the cells (primarily fibroblasts) from both irradiated and unirradiated lung regions by using a well-characterized micronucleus assay.

RESULTS

When the lungs were removed at 16-18 h after whole-lung irradiation, about 0.85 micronuclei (MN) per binucleate cell (BNC) were observed in the lung cells of the irradiated animals, compared to 0.02 MN/BNC in the lung cells of the controls. When only the lung base was irradiated, the frequency of micronuclei was 0.85 MN/BNC compared to 0.43 MN/BNC observed in cells from the irradiated lung apex. Of particular interest was the finding that the unirradiated lung apex also showed a large frequency of micronuclei (0.43 MN/BNC) after the irradiation of the lung base, whereas the unirradiated lung base showed only a marginal (approximately 2-fold) increase relative to the spontaneous frequency following irradiation of the lung apex. The changes in the frequency of micronuclei varied with the time at which the lungs were removed from the rats for early times, but had stabilized by 18 h after irradiation. Normal (unirradiated) cells grown in filtered or unfiltered conditioned media obtained from irradiated cell cultures showed an insignificant marginal increase in the number of micronuclei relative to the spontaneous frequency. Lung cells obtained from the lung base or the lung apex of healthy controls and irradiated separately in vitro showed no regional differences in the induction of micronuclei. Cells from the lungs of rats injected with superoxide dismutase, within 1 h prior to irradiation of the lung base, and processed 16-18 h after irradiation showed a reduction in the number of MN in the shielded lung apex, indicating the possible involvement of oxygen radicals.

CONCLUSIONS

These data indicate that cells in the lung base sustain more DNA damage than those in the lung apex when either region is irradiated; however, when the whole lung, is irradiated, the lung damage observed is similar in the two regions. Also, out-of-field effects are observed for the lung apex but not the lung base. Possible mechanisms include a clastogenic (chromosome damaging) factor produced in the plasma following irradiation and/or the production of oxygen radicals by activated lymphocytes/monocytes. The partial blocking of the DNA damage, observed in the unirradiated lung apex following irradiation of the lung base, by superoxide dismutase, suggests that oxygen radicals are involved in this out-of-field effect. These radicals are likely produced as a result of the induction of inflammatory cytokines, such as tumor necrosis factor (TNF) and interleukin-1 (IL-1) by the irradiation. The reason for the lack of an out-of-field effect in the lung base when the lung apex is irradiated is unknown, but may be due to the greater volume of lung irradiated in the lower lung field, because this is likely to affect the level of cytokines produced. Alternatively, it may reflect cytokines produced as a result of the partial liver irradiation that occurs with the lower lung field.

An examination of the effects of hypoxia, acidosis, and glucose starvation on the expression of metastasis-associated genes in murine tumor cells

Tumor cells exposed to a growth stress such as low pH, glucose starvation and hypoxia have been shown to exhibit a transient increase in experimental metastatic potential, particularly when allowed to recover under normal growth conditions for a period of 24-48 h. In this study we examined whether this increase in metastatic ability could be explained by changes in the expression of a number of different metastasis-associated genes, when the cells were exposed to similar conditions (24-48 h exposure to the stress condition followed by 0-48 h recovery under normal growth conditions). Although the cell lines used (KHT fibrosarcoma, SCC VII squamous cell carcinoma, and B16F1 melanoma) demonstrated altered metastatic ability after the treatment, no overall temporal correlation between changes in the mRNA levels for cathepsin B, cathepsin L, nm23, TIMP-1, osteopontin, or VEGF and metastatic ability in the three cell lines was observed. The production of gelatinase A (72 kDa collagenase) and gelatinase B (92 kDa collagenase) was also measured by gelatin zymography. There was an increase in production of these enzymes with increasing recovery time, but it did not parallel changes in metastatic potential. Although these results suggest that the products of most of the genes studied may not be involved in the transient metastatic changes, further studies are required to establish whether changes in protein levels track with changes in mRNA levels for these genes.

Heterogeneity of polarographic oxygen tension measurements in cervix cancer: an evaluation of within and between tumor variability, probe position, and track depth

PURPOSE

To evaluate the heterogeneity of cervix cancer oxygenation as measured using the Eppendorf polarographic electrode and define the optimal number of measurements required to adequately sample a cervix cancer.

METHODS AND MATERIALS

Two to 6 tracks with 20-30 measurements per track were obtained in each of the 44 patients evaluated. One hundred sixty-eight tracks and 4719 measurements formed the basis of this analysis. Median pO2 and hypoxic proportion (HP5), defined as the percentage of pO2 values <5 mmHg, were calculated for each track and for each tumor. Within-tumor (W) and between-tumor (B) variability in oxygenation was evaluated using a variance component analysis. The standard error of the measured HP5 with each additional track in each patient was analysed as a function of the total number of tracks.

RESULTS

The ratio W/W + B was 0.67 and 0.76 for median pO2 and HP5, respectively, indicating that multiple measurements are needed to adequately sample a tumor. The median value of the standard error of the HP5 decreased from 7.0 to 4.0% from the first to the fifth track, respectively. It was estimated that adding the sixth track would only result in a small change (<0.3%) in the standard error. There was no significant difference in oxygen tension measurements as a function of the location of the measurements around the circumference of the cervix or the depth along the measurement tracks.

CONCLUSIONS

There is significant within tumor variability in oxygen tension in cervix cancer. Five tracks with 20-30 measurements per track is optimal to sample the oxygenation status of a cervix cancer. The present data does not suggest that there is a significant difference related to the position in the tumor at which the pO2 measurements were taken.

Mutator phenotype in Msh2-deficient murine embryonic fibroblasts

Embryonic fibroblast cell lines were established from mice deficient, heterozygous, or proficient for Msh2, one of the three known DNA mismatch repair genes involved in hereditary nonpolyposis colon cancer (HNPCC). Cell lines were established by transfection of primary mouse embryo fibroblasts with E7 and Ras oncogenes or mutant p53. Spontaneously immortalized cells derived from the primary cultures were also studied. To determine whether these cells developed a mutator phenotype similar to that found in colon cancer cells deficient in mismatch repair, we measured mutation rates, microsatellite instability, and sensitivities to a range of DNA-damaging agents. The mutator phenotype detected in the E7 and Ras or mutant p53-immortalized Msh2-/- mouse cells was similar to that found in human mismatch repair-deficient colorectal carcinoma cell lines. Mutation rates to ouabain resistance were increased 8-12-fold relative to lines from Msh2+/+ mice, and microsatellite instability was detectable in 12-18% of subclones derived from the Msh2-/- line but was undetectable in subclones developed from the Msh2+/+ line. Furthermore, E7 and Ras or spontaneously immortalized Msh2-/- cells were significantly more resistant to the cytotoxic effects of 6-thioguanine relative to Msh2+/+ cells. In contrast, these lines showed various responses to UV light and cis-platinum, suggesting that mismatch repair deficiency was not the sole determinant for sensitivity to these DNA-damaging agents. Particular attention was paid to the properties of cells heterozygous for the Msh2 mutant gene, which would mimic the situation of an HNPCC carrier. However, our studies failed to reveal any properties of these cells that might provide a growth advantage or predispose them for the acquisition of further mutations. This observation is consistent with the model that inactivation of the wild-type Msh2 allele is a critical step for tumorigenesis in HNPCC patients.

Exposure to hypoxia, glucose starvation and acidosis: effect on invasive capacity of murine tumor cells and correlation with cathepsin (L + B) secretion

Cells in tumors may be exposed to adverse conditions such as nutrient deprivation, acidic pH and hypoxia. It has been shown previously that exposure to hypoxia, acidosis and glucose starvation in vitro increases the experimental metastatic ability of murine KHT-LP1 sarcoma, SCC-VII squamous carcinoma and B16 melanoma cells. This effect was most marked when cells were allowed to recover under normal in vitro growth conditions before injection. In the present study we examined whether the invasive capacity of the cells could be influenced by these modifications of the cell microenvironment. We used Matrigel, a basement membrane-like preparation in a two-chamber invasion assay to address this issue. Both KHT-LP1 and SCC-VII murine cell lines showed an increased ability to invade through Matrigel after hypoxia, and glucose starvation, but there was no consistent change in invasive capacity following acidosis exposure. The results for hypoxia and glucose starvation are in agreement with our previous studies of metastatic ability for these cell lines and we confirmed this for KHT-LP1 cells exposed to hypoxia in the current study. In parallel with the invasion assays, we compared cathepsin (L + B) content of the cells in treated and control suspensions. The effect observed varied according to the cell line and the treatment received (hypoxia, glucose starvation). There was an increase of cathepsin content for KHT-LP1 cells exposed to hypoxia and this increase correlated well with the increase of the invasion ability through Matrigel. We did not observe any increase of cathepsin for hypoxia-treated SCC-VII or for KHT-LP1 and SCC-VII cells treated with glucose starvation. These results suggest that transient hypoxia and glucose starvation can increase the invasive ability of tumor cell lines and thus may cause tumor progression by facilitating the invasive step of the metastatic process. The increased levels of cathepsin (L + B) in the KHT-LP1 cells treated with hypoxia, compared to control non-treated cells, may play a part in this increased invasive capacity.

The effects of artery occlusion on temperature homogeneity during hyperthermia in rabbit kidneys in vivo

To investigate the role of arterial occlusion on temperature homogeneity during hyperthermia for deep seated tissue, a renal hyperthermia animal model has been established using New Zealand white rabbits. The effects of ultrasound-induced renal hyperthermia, with or without continuous and intermittent renal artery occlusion, were compared and analysed. Both continuous and intermittent occlusion showed certain protection of surrounding tissue and demonstrated improved temperature homogeneity and heating efficiency. The benefits of continuous vs. intermittent occlusion are compared and discussed as well.

Radiosensitivity, apoptosis and repair of DNA double-strand breaks in radiation-sensitive Chinese hamster ovary cell mutants treated at different dose rates

The relationship of cell survival to induction and repair of DNA double-strand breaks (DSBs), as assessed by the neutral comet assay, was studied in two pairs of CHO cell lines, repair-deficient mutants xrs-5-11 and V3, and their respective parent lines K-1 and AA8, treated at two dose rates, 10.5 and 0.09 Gy/min. A marked difference in cell survival after irradiation was found between each pair of lines. For initial DNA damage, there was a significant difference between each pair of lines after the low-dose-rate treatment but not with high-dose-rate irradiation. Initial DSBs were dependent on dose at both dose rates. When residual damage at 2 h after irradiation was assessed, the 5-11 cells showed significantly more damage than K-1 cells after both high- and low-dose-rate irradiation. The V3 cells also showed more residual damage than the AA8 cells, but this difference was significant only after high-dose-rate irradiation. The results indicate that low-dose-rate irradiation can differentiate better between the DSB rejoining capacity of the sensitive and resistant cells and are consistent with the idea that it is the slow component of repair of DSBs which is different between them. Further studies with 5-11 and K-1 cells showed that radiation-induced apoptosis was dependent on dose, with a higher fraction of apoptotic cells in 5-11 than in K-1 cells after exposure to a given high-dose-rate radiation dose. However, the levels and time course of induction of apoptosis were similar for doses which gave equal levels of clonogenic survival. Radiation treatment was found to delay the progression of 5-11 and K-1 cells through the cell cycle to the same extent, with accumulation of cells in S phase and G2 phase, at 4 and 12 h after irradiation, respectively. There was no evidence for a G1-phase arrest. Western blotting revealed that there were higher levels of p53 and Waf1 protein in nonirradiated 5-11 than in K-1 cells, and that a dose of 5 Gy of high-dose-rate radiation up-regulated the expression of p53 and Waf1 protein to similar levels in both cell lines. There was no change in levels of the Gadd45 and Bcl2 proteins in either cell line after irradiation. These results suggest that the accumulation of p53 and Waf1 protein does not cause early G1-phase arrest in these cells.

The p53 gene as a modifier of intrinsic radiosensitivity: implications for radiotherapy

BACKGROUND AND PURPOSE

Experimental studies have implicated the normal or "wild type' p53 protein (i.e. WTp53) in the cellular response to ionizing radiation and other DNA damaging agents. Whether altered WTp53 protein function can lead to changes in cellular radiosensitivity and/or clinical radiocurability remains an area of ongoing study. In this review, we describe the potential implications of altered WTp53 protein function in normal and tumour cells as it relates to clinical radiotherapy, and describe novel treatment strategies designed to re-institute WTp53 protein function as a means of sensitizing cells to ionizing radiation.

METHODS AND MATERIALS

A number of experimental and clinical studies are critically reviewed with respect to the role of the p53 protein as a determinant of cellular oncogenesis, genomic stability, apoptosis, DNA repair and radioresponse in normal and transformed mammalian cells.

RESULTS

In normal fibroblasts, exposure to ionizing radiation leads to a G1 cell cycle delay (i.e. a "G1 checkpoint') as a result of WTp53 mediated inhibition of G1-cyclin-kinase and retinoblastoma (pRb) protein function. The G1 checkpoint response is absent in tumour cells which express a mutant form of the p53 protein (i.e. MTp53), leading to acquired radioresistance in vitro. Depending on the cell type studied, this increase in cellular radiation survival can be mediated through decreased radiation-induced apoptosis, or altered kinetics of the radiation-induced G1 checkpoint. Recent biochemical studies support an indirect role for the p53 protein in both nucleotide excision and recombinational DNA repair pathways. However, based on clinicopathologic data, it remains unclear as to whether WTp53 protein function can predict for human tumour radiocurability and normal tissue radioresponse.

CONCLUSIONS

Alterations in cell cycle control secondary to aberrant WTp53 protein function may be clinically significant if they lead to the acquisition of mutant cellular phenotypes, including the radioresistant phenotype. Pre-clinical studies suggest that these phenotypes may be reversed using adenovirus-mediated gene therapy or pharmacologic strategies designed to re-institute WTp53 protein function. Our analysis of the published data strongly argues for the use of functional assays for the determination of WTp53 protein function in studies which attempt to correlate normal and tumour tissue radioresponse with p53 genotype, or p53 protein expression.