Purpose: The purpose of this study was to determine whether a liposomal formulation of curcumin would suppress the growth of head and neck squamous cell carcinoma (HNSCC) cell lines CAL27 and UM-SCC1in vitro and in vivo. Experimental Design: HNSCC cell lines were treated with liposomal curcumin at different doses and assayed for in vitro growth suppression using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. A reporter gene assay was done on cell lines to study the effect of liposomal curcumin on nuclear factor nB (NFnB) activation. Western blot analysis was done to determine the effect of curcumin on the expression of NFnB, phospho-InBa, phospho-AKT (pAKT), phospho-S6 kinase, cyclin D1, cyclooxygenase-2, matrix metalloproteinase-9, Bcl-2, Bcl-xL, Mcl-1L, and Mcl-1S. Xenograft mouse tumors were grown and treated with intravenous liposomal curcumin. After 5 weeks, tumors were harvested and weighed. Immunohistochemistry and Western blot analyses were used to study the effect of liposomal curcumin on the expression of NFnB and pAKT. Results:The addition of liposomal curcumin resulted in a dose-dependent growth suppression of both cell lines. Liposomal curcumin treatment suppressed the activation of NFnB without affecting the expression of pAKTor its downstream target phospho-S6 kinase. Expression of cyclin D1, cyclooxygenase-2, matrix metalloproteinase-9, Bcl-2, Bcl-xL, Mcl-1L, and Mcl-1S were reduced, indicating the effect of curcumin on the NFnB pathway. Nude mice xenograft tumors were suppressed after 3.5 weeks of treatment with i.v. liposomal curcumin, and there was no demonstrable toxicity of liposomal curcumin upon autopsy. Immunohistochemistry andWestern blot analysis on xenograft tumors showed the inhibition of NFnB without affecting the expression of pAKT. Conclusions: Liposomal curcumin suppresses HNSCC growth in vitro and in vivo. The results suggest that liposomal curcumin is a viable nontoxic therapeutic agent for HNSCC that may work via an AKT-independent pathway.

Spectral tuning by visual pigments involves the modulation of the physical properties of the chromophore (11-cis-retinal) by amino acid side chains that compose the chromophore-binding pocket. We identified 12 amino acid residues in the human blue cone pigment that might induce the required green-to-blue opsin shift. The simultaneous substitution of nine of these sites in rhodopsin (M86L, G90S, A117G, E122L, A124T, W265Y, A292S, A295S, and A299C) shifted the absorption maximum from 500 to 438 nm, accounting for 2,830 cm ؊1 , or 80%, of the opsin shift between rhodopsin and the blue cone pigment. Raman spectroscopy of mutant pigments shows that the dielectric character and architecture of the chromophore-binding pocket are specifically altered. An increase in the number of dipolar side chains near the protonated Schiff base of retinal increases the ground-excited state energy gap via long range dipoledipole Coulomb interaction. In addition, the W265Y substitution causes a decrease in solvent polarizability near the chromophore ring structure. Finally, two substitutions on transmembrane helix 3 (A117G and E122L) act in combination with the other substitutions to alter the binding-pocket structure, resulting in stronger interaction of the protonated Schiff base group with the surrounding dipolar groups and the counterion. Taken together, these results identify the amino acid side chains and the underlying physical mechanisms responsible for a majority of the opsin shift in blue visual pigments.At the fundamental level, the ability of the visual system to discriminate wavelengths of electromagnetic radiation is determined by the spectral response of the light-absorbing pigments that reside in the photoreceptor cells of the retina. Trichromatic color vision in humans is mediated by three types of cone cells, each of which contains a specific visual pigment. The blue, green, and red cone pigments absorb maximally at ϳ425, 533, and 560 nm, respectively (1-3). Dim-light (scotopic) vision is mediated through rod photoreceptor cells containing the pigment rhodopsin with its absorption maximum ( max ) at 500 nm (4).All visual pigments share the same basic structure. The protein consists of an ϳ40-kDa polypeptide domain folded into seven transmembrane (TM) 1 helical segments. It is covalently bound to an 11-cis-retinal chromophore at a conserved lysine residue on TM helix 7 via a protonated Schiff base (PSB) bond (5-7). An 11-cis-retinal PSB molecule dissolved in an organic solvent such as ethanol has a max at ϳ440 nm. However, its max can range from ϳ420 to 560 nm in visual pigments due to interactions with residues in the binding site of the protein, which modulate the ground-excited electronic (S 0 -S 1 ) transition energy of the retinal PSB. The difference in the max of the pigment from that of the PSB model compound has been termed the "opsin shift" (8), which is also used to refer to the differences in the max values among pigments. Empirical and theoretical studies have identified several mechanisms by which opsin sh...

Several putative Escherichia coli pseudouridine (Psi) synthases have been identified by iterative searching of genomic databases for ORFs homologous to known Psi synthases [Gustafsson et al. (1996) Nucleic Acids Res. 24, 3756-3762]. Of these, yceC and yfiI were proposed to encode Psi synthases which modify 23S rRNA. In the present work, yceC and yfiI were cloned and overexpressed in E. coli, and the encoded enzymes, YceC and YfiI, were purified to homogeneity. Both proteins converted Urd residues of rRNA to Psi, thus confirming their identities as Psi synthases. However, in in vitro experiments both enzymes extensively modified Urd residues of both 23S rRNA and 16S rRNA. Gene-disruption of yceCresulted in the absence of Psi modification at positions U955, 2504, and 2580 of 23S RNA, thus identifying these sites as in vivo targets for YceC. Likewise, yfiI disruption resulted in the absence of Psi modification at positions U1911, 1917, and possibly 1915 of 23S RNA. Disruption of yceC did not affect the growth under the conditions tested, whereas yfiI-disrupted cells showed a dramatic decrease in growth rate. Since YceC and YfiI hypermodify RNA in vitro, factors in addition to ribonucleotide sequence must contribute to the in vivo specificity of these enzymes.