Action of low calcemic 1alpha,25-dihydroxyvitamin D3 analogue EB1089 in head and neck squamous cell carcinoma.
BACKGROUND
1alpha,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and its analogues inhibit growth of various types of cancer cells. Although the therapeutic potential of 1,25(OH)(2)D(3) is limited by its tendency to induce hypercalcemia, analogues such as EB1089 are potent inhibitors of cell growth and exhibit reduced calcemic effects. We analyzed the antiproliferative and calcemic effects of EB1089 in tissue culture and animal models of head and neck squamous cell carcinoma (SCC) to investigate its potential as a chemotherapeutic/chemopreventive agent.


METHODS
The effects of 1,25(OH)(2)D(3) and EB1089 on cell growth and expression of p21(WAF1/CIP1) and p27(KIP1), which encode cyclin-dependent kinase inhibitors, and a novel target, gadd45alpha, a growth-arrest and DNA-damage gene, were monitored in cultured murine AT-84 SCC cells. The effects of these agents on AT-84 cell growth in vitro and on growth of AT-84 tumors in syngeneic C3H mice were monitored; treatment started at the time of tumor implantation (early tumor model) or after 12 days (late tumor model). Weight and serum calcium levels were also monitored in these animals. All P values were two-sided.


RESULTS
Both 1,25(OH)(2)D(3) and EB1089 arrested proliferation of AT-84 cells in G(0)/G(1) phase, inhibited p21(WAF1/CIP1) expression, and induced expression of p27(KIP1) protein. 1,25(OH)(2)D(3) also enhanced the expression of gadd45alpha, apparently by a p53-independent mechanism. There was a statistically significant decrease in tumor growth for 1,25(OH)(2)D(3)-treated mice (P<.001 for early tumor model) and EB1089-treated mice (P<.001 and P =.001 for early and late tumor models, respectively). Unlike 1,25(OH)(2)D(3), EB1089 did not induce cachexia or hypercalcemia. The effects of 1,25(OH)(2)D(3) and EB1089 on expression of p21(WAF1/CIP1) and GADD45alpha were similar in tumors and in vitro.


CONCLUSIONS
EB1089 completely inhibited growth of AT-84 SCC cells at nanomolar concentrations, reduced tumor growth, and did not have calcemic effects. Our results support continued investigation of EB1089 as a chemopreventive/chemotherapeutic agent for head and neck SCC.
Prudencio
J
J
Department of Otolaryngology-Head and Neck Surgery, Jewish General Hospital, Montreal, PQ, Canada.
Akutsu
N
N
Benlimame
N
N
Wang
T
T
Bastien
Y
Y
Lin
R
R
Black
M J
MJ
Alaoui-Jamali
M A
MA
White
J H
JH
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D015152:Blotting, Northern; D015153:Blotting, Western; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000517:prevention & control; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000096:biosynthesis; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000517:prevention & control; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D009368:Neoplasm Transplantation; D011233:Precipitin Tests; D011506:Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D000097642:GADD45 Proteins
D000970:Antineoplastic Agents; D002117:Calcitriol; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D011506:Proteins; D012313:RNA; D025521:Tumor Suppressor Proteins; D000097642:GADD45 Proteins; C493957:Cdkn1a protein, mouse; C493961:Cdkn1b protein, mouse; C078903:seocalcitol