Honokiol is an active compound purified from magnolia that has been shown to induce cell differentiation, apoptosis, and
anti-angiogenesis effects, as well as an enhancement in
tumor growth delay in combination with chemotherapeutic agents in several mouse xenograft models. Our goal was to investigate the radiosensitization effect of
honokiol on lung
carcinoma. The radiosensitization effect of
liposomal honokiol in
Lewis lung carcinoma cells (LL/2) was analyzed using an in vitro clonogenic survival assay. For an in vivo study,
Lewis lung carcinoma-bearing C57BL/6 mice were treated with either
liposomal honokiol at 25 mg/kg or 5 Gy of single
tumor radiation, or a combination of both over 12 days of treatment. The
tumor growth delay and the survival time were evaluated. In addition, histological analysis of
tumor sections was performed to examine changes by detecting the microvessel density and apoptosis in
tumor tissues. In the clonogenic survival assay, LL/2 cells treated with IC(50)
Lipo-HNK for 24 h showed a radiation enhancement ratio of 1.9. After 12 days of combination treatment, the
tumor volume decreased 78% and produced an anti-
tumor activity 1.3-fold greater than a predicted additive effect of
honokiol and radiation alone. This combination treatment also caused an 8.7 day delay in
tumor growth. The cell cycle distribution and histological analysis demonstrated that
liposomal honokiol has an anti-
tumor effect via inducing apoptosis and inhibiting angiogenesis.
Liposomal honokiol can enhance
tumor cell radiosensitivity in vitro and in vivo, indicating that
radiotherapy combined with
liposomal honokiol can lead to greater anti-
tumor efficacy.