Combination of carbonic anhydrase inhibitor, acetazolamide, and sulforaphane, reduces the viability and growth of bronchial carcinoid cell lines.
BACKGROUND
Bronchial carcinoids are pulmonary neuroendocrine cell-derived tumors comprising typical (TC) and atypical (AC) malignant phenotypes. The 5-year survival rate in metastatic carcinoid, despite multiple current therapies, is 14-25%. Hence, we are testing novel therapies that can affect the proliferation and survival of bronchial carcinoids.


METHODS
In vitro studies were used for the dose-response (AlamarBlue) effects of acetazolamide (AZ) and sulforaphane (SFN) on clonogenicity, serotonin-induced growth effect and serotonin content (LC-MS) on H-727 (TC) and H-720 (AC) bronchial carcinoid cell lines and their derived NOD/SCID mice subcutaneous xenografts. Tumor ultra structure was studied by electron microscopy. Invasive fraction of the tumors was determined by matrigel invasion assay. Immunohistochemistry was conducted to study the effect of treatment(s) on proliferation (Ki67, phospho histone-H3) and neuroendocrine phenotype (chromogranin-A, tryptophan hydroxylase).


RESULTS
Both compounds significantly reduced cell viability and colony formation in a dose-dependent manner (0-80 μM, 48 hours and 7 days) in H-727 and H-720 cell lines. Treatment of H-727 and H-720 subcutaneous xenografts in NOD/SCID mice with the combination of AZ + SFN for two weeks demonstrated highly significant growth inhibition and reduction of 5-HT content and reduced the invasive capacity of H-727 tumor cells. In terms of the tumor ultra structure, a marked reduction in secretory vesicles correlated with the decrease in 5-HT content.


CONCLUSIONS
The combination of AZ and SFN was more effective than either single agent. Since the effective doses are well within clinical range and bioavailability, our results suggest a potential new therapeutic strategy for the treatment of bronchial carcinoids.
Developmental and Stem Cell Biology, University of Toronto, Toronto, ON, Canada. hermie@sickkids.ca.
Reza Bayat
RB
Mokhtari
Sushil
S
Kumar
Syed S
SS
Islam
Mehrdad
M
Yazdanpanah
Khosrow
K
Adeli
Ernest
E
Cutz
Herman
H
Yeger
D000086:Acetazolamide / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001984:Bronchial Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D002257:Carbonic Anhydrase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D002276:Carcinoid Tumor / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D005260:Female; D017879:Isothiocyanates / Q000008:administration & dosage / Q000494:pharmacology*; D051379:Mice; D012701:Serotonin / Q000378:metabolism; D013454:Sulfoxides; D047368:Tumor Burden / Q000187:drug effects; D014410:Tumor Stem Cell Assay; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D002257:Carbonic Anhydrase Inhibitors; D017879:Isothiocyanates; D013454:Sulfoxides; D012701:Serotonin; C016766:sulforaphane; D000086:Acetazolamide