Curcumin and fenretinide are 2 well-known and promising chemotherapeutic compounds via various molecular mechanisms. However, the anticancer capacity of either curcumin or fenretinide is limited. This prompted us to examine the combined anticancer effects of curcumin and fenretinide. Our results demonstrate for the first time that there is synergistic anticancer effect of combined treatment with these 2 agents, leading to enhanced cytotoxicity and enhanced expression level of pro-apoptotic protein cleaved PARP in non-small cell lung cancer (NSCLC) cells while showed little toxicity to rat cardiomyoblast normal cells. The combination treatment was also demonstrated to inhibit lung carcinoma growth in vivo. Furthermore, we show that fenretinide or the ER stress inhibitor 4-PBA decreased curcumin-induced Glucose-regulated protein 78 (GRP78) upregulation, and produced a similar enhanced cytotoxic effect. In addition, GRP78 knockdown by siRNA also enhanced the cytotoxic effect of curcumin in A549 and H1299 cells. Our findings suggest that the 2 small molecules, when used in combination, can potentially be effective therapeutic agents for treating NSCLC, at least in part, by regulating endoplasmic reticulum (ER) chaperone protein GRP78.Abbreviations: NSCLC, non-small cell lung cancer; GRP78, Glucose-regulated protein 78; ER, endoplasmic reticulum; 4-PBA, 4-phenylbutyrate; LLC, Lewis lung carcinoma KEYWORDS Curcumin; fenretinide; GRP78; non-small cell lung cancer

Fasudil (FSD), a selective rho kinase (ROCK) inhibitor, was found to form 1 : 1 host-guest inclusion complexes with a synthetic macrocyclic receptor, cucurbit[7]uril (CB[7]), in aqueous solutions, as evidenced by H NMR, photoluminescence and UV-visible spectroscopic titrations, isothermal titration calorimetry (ITC) titration, and electrospray ionization (ESI) mass spectrometry, as well as density functional theory (DFT) molecular modeling. Upon encapsulation, whereas the UV-vis absorbance of FSD experienced a moderate decrease and bathochromic shift, the fluorescence intensity of FSD at 354 nm was dramatically enhanced for up to 69-fold at neutral pH, which could potentially be applied in fluorescent tracking of the drug delivery and release. More interestingly, the binding affinity (K = (4.28 ± 0.21) × 10 M), of FSD-CB[7] complexes under acidic conditions (pH = 2.0), is approximately three orders of magnitude higher than that (2.2∼6.6 × 10 M) under neutral pH conditions (pH = 7.0). Accordingly, UV-visible spectroscopic titration of the free and complexed FSD under various pH conditions has demonstrated that the encapsulation of FSD by CB[7] shifted the pK of the isoquinoline-N upward from 3.05 to 5.96 (ΔpK of 2.91). The significantly higher binding affinity of the complexes under acidic conditions may be applied in developing the "enteric" formulation of FSD. Furthermore, our in vitro study of the bioactivity of FSD in the absence and presence of CB[7] on a neural cell line, SH-SY5Y, showed that the complexation preserved the drug's pro-neurite efficacy. Thus this discovery may lead to a fluorescence-trackable, orally administered enteric formulation of rho kinase inhibitors that are stable under gastric conditions, without compromising bioactivity of the drugs.

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