Dennis R. Burholt

Response of the murine gastrointestinal epithelium to cis-dichlorodiammineplatinum II: Radiation combinations

Single doses of cis-dichlorodiammineplatinum II (cis DDP) up to 8 mg/kg produced a dose-dependent inhibition of proliferative activity with a subsequent period of compensatory hyperplasia in the colon. The stomach was less responsive to cis DDP. Cis DDP-radiation combinations produced a dimunition in the proliferative response of the colon when compared to that following radiation only. This response was only seen in the stomach following 8 mg/kg of cis DDP and radiation. Cytokinetic analysis of the jejunal response to 8 mg/kg of cis DDP showed a gradual reduction in LN and MF/crypt with a reduction in the rate of DNA synthesis of S-phase cells through 8 hours post-treatment. By 24 hours the cellular DNA synthetic rate had recovered, although the number of S-phase cells was further reduced. The previously reported jejunal response to cis DDP-radiation combinations involved a reduction in crypt survival, coupled with a reduced proliferative capacity of surviving cells. Further investigation has revealed a possible inhibition of radiation damage repair by cis DDP, leading to increased levels of cell kill with the combination and reduced recovery of DNA synthetic rates in surviving cells.

The Modification of Gastrointestinal Tolerance and Responses to Abdominal Irradiation by Chemotherapeutic Agents

Groups of male DBA/2 mice were irradiated with partial abdominal exposures of x radiation ranging from 100 to 1,600 rads. Concomitant with radiation exposure and at 1 or 4 hours prior to, and at 1, 6, 24, or 48 hours after irradiation, various chemotherapeutic agents were administered, i.e., methotrexate, Cytoxan, adriamycin and BCNU. The results suggest that excessive gastrointestinal toxicity may result if aggressive chemotherapy is closely spaced with radiation exposure for the treatment of abdominal neoplasms. However, adjustment of dose and time patterns based on the proliferative responses of the mucosa may circumvent such toxicity to a large extent.

Therapeutic potentiation of combined cis-dichlorodiammineplatinum (II) and irradiation by ICRF-159.

Abstract The effect of fractionated ICRF-159 (25 mg/kg, g3h×4) pretreatment on the antitumor activity of cis DDP+irradiation combinations has been evaluated using the Lewis lung tumor. All three agents given alone as single treatments result in transient interruption of proliferative activity with only slight to moderate alterations of tumor growth. Fractionated ICRF-159 treatment, while eliciting low cytotoxicity, results in a partial cytokinetic redistribution of tumor cells enhancing subsequent radiotherapy and chemotherapy with cis DDP. For cis DDP-radiation combinations, where cis DDP precedes irradiation, increasing the intertreatment time from 6 hr to 24 hr results in synergistic interactions and increased treatment efficacy. When cis DDP-radiation combinations followed fractionated ICRF-159, regression was greatly enhanced suggesting that relatively non-cytotoxic agents may be used to sensitize low growth fraction, resistant tumors to subsequent combined-mode therapy.

Digestive Tract Cell Proliferation and Food Consumption Patterns of Ha/Icr Mice

The relationship between the daily pattern of food consumption and the proliferation rate of the qesophagus, stomach, forestomach, small intestine and colon of Ha/ICR mice was examined. Proliferative activity was determined by [3H]TdR incorporation on a wet weight tissue basis, along with selective counting of labelled nuclei. Under conditions of ad libitum feeding with a 12 hr light cycle (lights on at 0600) mice eat most of their food during the dark period. A distinct circadian rhythm was observed in the oesophagus, stomach, forestomach and colon with the peak of [3H]TdR incorporation between 0400 and 0600 and the nadir between 1600 and 1800. Although a circadian fluctuation was observed in the small intestine, its amplitude was much less than in other areas. This rhythmic change in proliferation rate could be phase shifted by allowing the mice to feed only between 0800 and 1600 for 14 days. Under these conditions the peak in proliferative activity occurred between 1800 and 2000. Fasting reduced the daily level of proliferative activity in all of the digestive tract sites studied, and for all areas except the oesophagus greatly reduced or eliminated the circadian fluctuation. the forestomach and colon were the most influenced by fasting with 24 hr [3H]TdR incorporation reduced to 30–40% of the control value. Refeeding following a 48 hr fast produced a rapid increase in proliferative activity peaking at levels well above the control value at 16 hr after the onset of refeeding. the major exception to this was the small intestine which slowly returned to the control value during the first 24 hr. Partial refeeding produced a diminished refeeding response. Once the normal pattern of food consumption was re‐established following refeeding the normal proliferative fluctuations were again observed.

Adriamycin-radiation combinations: Drug induced delayed gastrointestinal radiosensitivity

Abstract The administration of Adriamycin (ADR) results in acute short-term reductions in cell production within the gastrointestinal mucosa. Interactions between ADR doses and radiation appear minimized as the intertreatment time interval expands to five days. However, as the times between drug administration and abdominal radiation exposure are further lengthened (from 14–49 days), a progressively severe defect in postirradiation mucosal cell production is noted. Although the mucosa appears normal histologically and crypt cell cellularity and cell production are normal, the proliferative response following radiation is reduced by as much as 50% if ADR is given 7 weeks prior to the radiation exposure. We postulate that this effect is a manifestation of latent damage to the stem cell compartment within the crypt or that secondary support systems such as mucosal vascularity have been compromised by ADR.

ICRF-159 enhancement of radiation response in combined modality therapies. I. Time/dose relationships for tumour response.

The combined effect of the chemotherapeutic agent ICRF-159 and irradiation were evaluated using the Lewis lung tumour (LL). At a daily dose of 25 mg/kg, ICOF given alone prevented the progressive growth of LL. Daily pretreatment also potentiated the effects of radiation (600 rad) on tumour growth, provided the pretreatment kinetics of the tumour permitted a response to radiation alone. Single acute doses of the drug failed to alter the growth of LL, and when combined with radiation failed to enhance the radiation effect. Fractionation of the drug (25 mg/kg; 4 doses at 3h intervals) before irradiation, however, results in immediate effects on tumour growth which are more than additive. The results suggest that a low dose of ICRF-159 for extended periods is more effective in enhancing radiotherapy than a high dose provided acutely.

Alterations In Gastrointestinal Steady‐State Kinetics Associated With the Growth of Experimental Tumours

Changes in the growth kinetics of the intestinal epithelium were observed in mice bearing the Lewis lung carcinoma and the T1699 mammary adenocarcinoma and in rats bearing the H‐4‐II‐E2 hepatoma. Proliferative activity in the jejunal tissue was markedly depressed with increasing tumour burden. Simultaneously, a significant reduction in total crypt cellularity occurred, followed by a reduction in villus height. While the total number of proliferative cells per crypt decreased, the relative proliferative compartment within the shrinking crypt increased. the rate of mucosal DNA synthesis remained constant during the initial cytokinetic changes, falling only after proliferative activity of the intestine was reduced to less than 50% of control levels. No general correlation could be drawn from the three tumour models studied between the level of gastrointestinal proliferation and tumour size, tumour growth rate or loss of weight by the tumour‐bearing animals. However, intestinal proliferation was reduced by 50% when the tumour burden for each of the three tumours reached 6–8% of the host animal weight.

Enhanced adriamycin—induced delayed gastrointestinal radiosensitivity in tumor-bearing mice

Abstract Intestinal proliferative activity in BDF, mice bearing the Lewis lung tumor (LL ca /BDF 1 ) was markedly depressed with increasing tumor burden. When compared with non-tumor-bearing mice (BDF 1 ), integrated cell production over 7 days was reduced to 56% in animals with small (400 mm 3 ) tumors and to 30% in animals with large (2500 mm 3 ) tumors. Gastrointestinal radiosensitivity was measured by proliferative compensatory response kinetics to a radiation dose of 600 rad. The presence of tumor (mean tumor volume=859 ± 209 mm 3 ) delayed the jejunal response to radiation by 24 hr and reduced the integrated cell production from 136% in BDF 1 mice to 119% in the LL ca /BDF 1 mice. While the presence of tumor did not alter the temporal response of the colonic epithelium to radiation, the compensatory peak was reduced from 248% (BDF 1 ) to 200% (LL ca /BDF 1 ). Adriamycin (Adr; 10 mg/kg) given 60 days prior to radiation failed to enhance the jejunal radiosensitivity in BDF 1 mice. However, when tumor-bearing LL ca /BDF 1 mice were treated under an identical dose and time configuration, the jejunal response to 600 rad was significantly impaired: proliferative peaks were reduced from 182 to 115% ; integrated cell production was reduced from 119 to 72%. In the colon of tumor-bearing mice, pretreatment with AdR reduced the proliferative compensatory peak from the subsequent radiation dose to 120% of pretreatment levels.

ICRF-159 enhancement of radiation response in combined modality therapies. II. Differential responses of tumour and normal tissues.

The combined effect of the chemotherapeutic agent ICRF-159 and radiation on the proliferative status of tumor/normal systems has been evaluated using the Lewis lung tumour in BDF1 mice. We have previously shown that a 25 mg/kg dose of ICRF-159, given at 3h intervals X4 before irradiation, significantly enhanced tumour growth retardation relative to a single dose of 100 mg/kg before irradiation. Whilst both single and fractionated drug treatments produced a transient inhibition of cell proliferation, comparisons of the temporal recovery from the antiproliferative effect of radiation in both tumour and intestinal epithelium suggested that single acute doses of ICRF-159 fail to potentiate the radiation response of either tissue. Protracted drug administration before irradiation, however, markedly decreases the post-radiation proliferative recovery of the tumour, without significantly altering intestinal recovery. The data suggest that both drug concentration and/or exposure time determine the interactions seen with combined modes.