STI-571 (Gleevec) potentiates the effect of cisplatin in inhibiting the proliferation of head and neck squamous cell carcinoma in vitro.
OBJECTIVE
The objective of this study was to determine whether STI-571 (Gleevec; imatinib mesylate) could sensitize established head and neck squamous cell carcinoma (HNSCC) cell lines to the effects of cisplatin.


METHODS
Western blot analysis and immunofluorescence were used to examine the expression of the tyrosine kinases that are known targets of Gleevec, including c-kit, c-Abl, and platelet-derived growth factor receptor, on the cell lines, and immunohistochemistry was performed to determine the expression of these kinases in human HNSCC tissue. Once these targets were confirmed, clonogenic cell survival assays were performed to determine the effect STI-571 had on growth and proliferation when used in combination with cisplatin compared with STI-571 alone or cisplatin alone. Cells were incubated with a range of doses of STI-571 24 hours before the addition of cisplatin. Flow cytometry analysis was performed to determine cell-cycle distribution and to measure apoptosis caused by the various treatments. An annexin V assay was also used to further measure apoptosis.


RESULTS
Our results indicate that STI-571 potentiates the effect of cisplatin and leads to a significant decrease in cell proliferation and colony formation compared with cisplatin alone in a dose-dependent fashion. Surprisingly, there was a slight decrease in the level of apoptosis when Gleevec was used in combination with cisplatin compared with cisplatin alone. Gleevec alone resulted in a slight increase in G1 phase of the cell cycle, whereas cisplatin alone resulted in a G2 arrest. The addition of Gleevec to cisplatin resulted in an enhanced S/G2 phase accumulation. Although we did not demonstrate an increase in cisplatin-induced cell death, we postulate that the increased S/G2 arrest resulting from the DNA damage in the presence of Gleevec results in decreased proliferation of HNSCC, resulting in a net decrease in colony formation.


CONCLUSIONS
The small molecule inhibitor Gleevec, which targets specific tyrosine kinases that are expressed in HNSCC, can significantly potentiate the antiproliferative effects of cisplatin. Because Gleevec alone has minimal side effects, treatment with the combination treatment of cisplatin and Gleevec may result in increased efficacy of cisplatin in treating this cancer. Additional studies are warranted, keeping in mind that drug combinations may result in unexpected toxicities that are not frequently seen with either drug alone.
Wang-Rodriguez
Jessica
J
VA San Diego Healthcare System, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
Lopez
Jay Patrick
JP
Altuna
Xabier
X
Chu
Theresa S
TS
Weisman
Robert A
RA
Ongkeko
Weg M
WM
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D004357:Drug Synergism; D005455:Fluorescent Antibody Technique; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D000068877:Imatinib Mesylate; D008938:Mitosis / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000032:analysis; D016315:Proto-Oncogene Proteins c-abl / Q000032:analysis; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis; D011743:Pyrimidines / Q000494:pharmacology*; D017479:Receptors, Platelet-Derived Growth Factor / Q000032:analysis
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D017479:Receptors, Platelet-Derived Growth Factor; D016315:Proto-Oncogene Proteins c-abl; D002945:Cisplatin