Effect of Induced Host Anaemia on the Viability and Radiosensitivity of Murine Malignant Cells in vivo

Abstract

SUMMARY.-Within 48 hours of the institution of severe phenylhydrazineinduced anaemia in mice bearing ascites tumours or generalised leukaemia, a substantial proportion of the malignant cells disappeared respectively from the peritoneal cavity or infiltrated liver. The results of radiobiological experiments permitting determination of the proportion of viable leukaemia cells which were severely hypoxic and relatively radioresistant in the livers of leukaemic mice, showed that induction of anaemia was associated with a several hundredfold increase in the proportion of such cells. The proportion of hypoxic cells was greatly reduced when the anaemic leukaemic mice were transfused with packed erythrocytes or allowed to breathe oxygen under high pressure. Similar experiments with solid sarcomas indicated that a high proportion of the tumour cells were hypoxic in non-anaemic mice breathing air. The hypoxic fraction was not significantly reduced when tumour-bearing mice were made severely anaemic during growth of the tumour and were later transfused. Thus, the hypoxic cells in leukaemic livers and those in solid tumours are markedly different in their capacity for oxygenation following the induction of relative hyperoxaemia.IT is well known that anaemia is a common complication of human cancer and that a wide variety of factors are implicated in its pathogenesis. In cases in which obvious factors, such as haemorrhage or bone marrow replacement, can be excluded, it is probable that continuous extravasation of blood into the tumour itself is paramount. This process has been demonstrated in several transplanted animal tumours using radio-labelled erythrocytes (Greenfield, Godfrey and Price, 1958). Clinical awareness of the frequency of haematological deficiency, even in cases in which the tumour is quite small in relation to body weight, leads to rectification of anaemia before measures to control the tumour are undertaken.Contrasting with the clinical attentiveness to constitutional depradations associated with localised cancer is the frequent neglect of such considerations in the experimental study of rodent tumours. In our experience, rapidly increasing host anaemia is frequently present when transplanted mouse tumours attain a size at which significant observations of the tumour are likely to be made. For example, terminal depression of tumour growth rate (Laird, 1964) and the microanatomy of extremely large tumours (Inch and McCredie, 1968) have been interpreted without reference to the possible implication of progressive host anaemia in the changes described.

The influence of haemoglobin affinity for oxygen on tumour radiosensitivity

“…Hewitt and Blake (1971) looked at the effect of inducing anaemia with phenylhydrazine and then correcting it by blood transfusion before irradiation. This procedure gave clear radiosensitization in one tumour, a leukaemia cell line but minimal effect in another, a sarcoma.…”

“…We have recently shown that preconditioning to anaemia (Hirst, 1986;Hirst & Wood, 1987) permits several tumours to be sensitized by blood transfusion but that the sensitization is transient, the effect being lost in 6-48 h depending on tumour line. This adaptation phenomenon could account for the inability of Hewitt and Blake (1971) to sensitize one of their tumours (Sarcoma F), because they permitted an interval of up to 20h to elapse between transfusion and irradiation. It also leads us to suspect that the sensitization we have achieved with the transfusion of low affinity blood will be transient.…”

Phase III trial to evaluate the efficacy of maintaining hemoglobin levels above 12.0 g/dL with erythropoietin vs above 10.0 g/dL without erythropoietin in anemic patients receiving concurrent radiation and cisplatin for cervical cancer

“…Tumor hypoxia results in relative irradiation and chemotherapy resistance. [4][5][6][7] In addition, hypoxia is an important stimulus for angiogenesis; it drives the process of malignant progression resulting in the up regulation of enzymes and proteins which lead to tumor invasion, the down regulation of cell surface antigens resulting in cell detachment, genomic instability with mutagenic properties and the increased clonal selection of cells with apoptosis enhanced survival. 8 It has been assumed that low hemoglobin levels may therefore result in impaired tumor oxygenation, although tumors exposed to low levels of oxygen as seen in the chronic anemia of malignancy are able to adapt to the microenvironment and restore tumor oxygenation.…”

The influence of chronic anaemia on the radiosensitivity of two mouse tumours

“…The number of clonogenic cells after a single X-ray dose of 20Gy was slightly lower (P<0.05) in the anaemic animals (2.3 x I04g-') than in controls (5.2 x I04g-') though there was no significant difference in the surviving fractions. Mice bearing KHT tumours became anaemic with haematocrits falling to 65% of normal as their tumours grew from 300-1200 mg. A second 'test' tumour was implanted one week after the first 'anaemia-inducing' tumour so that estimates of radiosensitivity could all be carried out on tumours within the same size range (150-300mg (Bush, 1986;Dische, 1990;Hirst, 1986;Overgaard et al, 1989) though not every study supports this view (Fazekas et al, 1989) (Hirst & Wood, 1987) administration of phenylhydrazine (Hewitt & Blake, 1971;Siemann et al, 1989;Tanaka et al, 1969) low iron diets (McCormack et al, 1990;Walker et al, in press) the effects of growth of some tumours (Hill et al, 1971) and kidney irradiation (Rojas et al, 1987). The results of these studies will be considered later, but it is at once obvious that several inconsistencies exist and that the induction of anaemia probably brings into effect adaptive mechanisms that have a profound influence on tumour radiosensitivity.…”