Toxicity and dose-response studies of 1-alpha hydroxyvitamin D2 in LH-beta-tag transgenic mice.
OBJECTIVE
To determine the effectiveness of a vitamin D analog, 1alpha-hydroxyvitamin D(2) (1alpha-OH-D(2)), in inhibiting retinoblastoma in a transgenic retinoblastoma model (LHbeta-Tag mouse) and to evaluate its toxicity.


METHODS
Experimental study using an animal (LHbeta-Tag transgenic mouse) randomized (controlled) trial.


METHODS
Two hundred seventeen LHbeta-Tag transgene-positive 8- to 10-week-old mice total; 179 drug-treated animals, 38 control animals.


METHODS
Mice were fed a vitamin D- and calcium-restricted diet and were randomized to treatment groups receiving control (vehicle), or 0.1, 0.3, 0.5, or 1.0 micro g/day of 1alpha-OH-D(2) via oral gavage 5 times weekly for 5 weeks. Body weight was measured at the start of treatment and twice weekly during treatment. Animals were euthanized on the last day of treatment. The eyes were enucleated, processed histologically, and serially sectioned. Representative sections from the superior, middle, and inferior regions of each globe were examined microscopically and tumor areas were measured using Optimas software. Serum was collected for serum calcium levels. Kidneys were removed for histologic processing and were analyzed microscopically for kidney calcification.


METHODS
Mean tumor area was measured to determine drug effectiveness. Toxicity was assessed by survival, weight loss over the treatment period, serum calcium, and kidney calcification.


RESULTS
The mean tumor size in each 1alpha-OH-D(2) group was smaller than controls (all P values < 0.02): control, 90,248 micro m(2); 0.1 micro g, 31,545 micro m(2); 0.3 micro g, 16,750 micro m(2); 0.5 micro g, 30,245 micro m(2); and 1.0 micro g, 16,049 micro m(2). No dose-dependent response curve was evident. The survival percentage for each group was as follows: control, 97%; 0.1 micro g, 91%; 0.3 micro g, 88%; 0.5 micro g, 70%; and 1.0 micro g, 63%. Mortality was higher in the 0.5- micro g and 1.0- micro g doses (P values < 0.01) compared with other treatment groups and with the control group. Serum calcium levels were significant in all treatment groups compared with controls (all P values < 0.0001).


CONCLUSIONS
In the LHbeta-Tag mouse, 1alpha-OH-D(2) inhibits retinoblastoma with no significant increase in mortality in lower doses (0.1-0.3 micro g). 1alpha-OH-D(2) has approval by the Food and Drug Administration as an investigative drug for cancer treatment, and has shown efficacy with low toxicity in adult cancer trials. 1alpha-OH-D(2) meets the criteria for human clinical trials.
Dawson
Daniel G
DG
Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine, Madison, Wisconsin, USA.
Gleiser
Joel
J
Zimbric
Michele L
ML
Darjatmoko
Soesiawaiti R
SR
Lindstrom
Mary J
MJ
Strugnell
Stephen A
SA
Albert
Daniel M
DM
D000818:Animals; D002114:Calcinosis / Q000139:chemically induced; D002118:Calcium / Q000097:blood; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004872:Ergocalciferols / Q000008:administration & dosage* / Q000633:toxicity*; D007668:Kidney / Q000187:drug effects; D037101:Luteinizing Hormone, beta Subunit / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D019572:Retinal Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000401:mortality; D012175:Retinoblastoma / Q000097:blood / Q000188:drug therapy* / Q000401:mortality; D015996:Survival Rate; D019076:Transgenes
D004872:Ergocalciferols; D037101:Luteinizing Hormone, beta Subunit; C042533:1 alpha-hydroxyergocalciferol; D002118:Calcium