Knocking down LSD1 inhibits the stemness features of colorectal cancer stem cells.

As a top leading cause of cancer death in many countries, colorectal cancer (CRC) has drawn increasing attention to the study of the pathological mechanism. According to the "cancer stem cell hypothesis", malignancies originate from a small fraction of cancer cells that show self-renewal properties to initiate and sustain tumor growth and tumor metastasis. Therefore, these cancer stem cells (CSC) probably play important roles in tumor recurrence, metastasis, and drug resistance. Previous research reported that lysine-specific histone demethylase 1 (LSD1) maintains cancer stemness through up-regulating stemness markers SOX2 and OCT4. CD133 is believed to be the most robust surface marker for CRC stem cells, however the regulatory effect of LSD1 on stemness of CD133+ CRC has never been reported. In this study, our objectives included: 1) to isolate pure CD133+ and CD133- cells from SW620 cell line; 2) to investigate the effect of LSD1 on the characteristics of CD133+ stem cancer cells by knocking down the target gene. Results suggested that the SW620 cell line had both CD133+ and CD133- subsets. The CD133+ subset exhibited more CSC-like characteristics compared with the CD133- subset with higher viability, colony formation rate, migration and invasion rate, resistance to anti-cancer drugs, and apoptosis in vitro. The CD133+ also induced faster tumor formation and larger tumors in vivo. In the LSD1-knockdown CD133+ cells, the CSC-like characteristics had been all weakened. We conclude that LSD1 was important for CSCs to maintain their "stemness" features, which could be a potential therapeutic target of CRC.

Knocking down LSD1 inhibits the stemness features of colorectal cancer stem cells

As a top leading cause of cancer death in many countries, colorectal cancer (CRC) has drawn increasing attention to the study of the pathological mechanism. According to the "cancer stem cell hypothesis", malignancies originate from a small fraction of cancer cells that show self-renewal properties to initiate and sustain tumor growth and tumor metastasis. Therefore, these cancer stem cells (CSC) probably play important roles in tumor recurrence, metastasis, and drug resistance. Previous research reported that lysine-specific histone demethylase 1 (LSD1) maintains cancer stemness through up-regulating stemness markers SOX2 and OCT4. CD133 is believed to be the most robust surface marker for CRC stem cells, however the regulatory effect of LSD1 on stemness of CD133+ CRC has never been reported. In this study, our objectives included: 1) to isolate pure CD133+ and CD133− cells from SW620 cell line; 2) to investigate the effect of LSD1 on the characteristics of CD133+ stem cancer cells by knocking down the target gene. Results suggested that the SW620 cell line had both CD133+ and CD133− subsets. The CD133+ subset exhibited more CSC-like characteristics compared with the CD133− subset with higher viability, colony formation rate, migration and invasion rate, resistance to anti-cancer drugs, and apoptosis in vitro. The CD133+ also induced faster tumor formation and larger tumors in vivo. In the LSD1-knockdown CD133+ cells, the CSC-like characteristics had been all weakened. We conclude that LSD1 was important for CSCs to maintain their "stemness" features, which could be a potential therapeutic target of CRC.

Site specificity on OH α-H abstraction reaction for a zwitterionic ß-hairpin peptide in aqueous solution: a theoretical investigation.

Protein backbone oxidation was investigated by studying the α-H abstraction reaction in a ß-hairpin peptide, called Chignolin (PDB ID 1UAO), with density functional theory calculation at B3LYP/6-31G(d,p) without any constraint. In order to stabilize the zwitterionic form of Chignolin with the salt bridges, the effects of aqueous solution were implemented by using microsolvation combined with a conductor-like polarizable continuum model (CPCM). Comparison between three glycine residues located at three different sites in Chignolin was used to examine the possible site specificity of this backbone oxidation. To construct the reaction profile of these α-H abstraction reactions, the pre- and postreactive complexes along with their associated transition states were located and verified with the intrinsic reaction coordinate (IRC) method. The bond dissociation energy and reaction rates of these OH α-H abstraction reactions were calculated with transition state theory. The differences in this abstraction reaction between the neutral and zwitterionic forms of Chignolin were also compared. A molecular dynamics simulation was implemented to study the explicit solvation effect on the abstracted Chignolin structure. The range of the simulation time scale covers from femtoseconds to microseconds, i.e., from onset of the abstraction to the abstracted products reaching thermal equilibrium. Our results show that there are three kinds of site-specificity in this abstraction reaction. The reactivity and stability of the abstraction products and their abstraction modes are all dependent on the location where OH attacks. Furthermore, the free energy landscapes of these abstraction products are distinctively different. This may imply that the pathological disorders or diseases caused by this type of radicals are also dependent on the abstraction location.

Site specificity of OH α-H abstraction reaction for a ß-hairpin peptide: an ab initio study.

A ß-hairpin peptide (PDB ID 1UAO) was modeled to explore the backbone oxidation of a protein by an OH radical to abstract one α-H atom with ab initio calculation at the B3LYB/6-31G(d) without any constraint. Three glycine residues located at three different sites in 1UAO were used to examine the possible site specificity of this backbone oxidation. The pre- and post-reactive complexes along with their associated transition states were located and verified by the intrinsic reaction coordinate method. The reaction profile of these α-H abstraction reactions was constructed. The effects of the aqueous solution were estimated by the conductor-like polarizable continuum model (CPCM) model. Rate constants were calculated with transition state theory. The reaction rate of the OH α-H abstraction varies among these three different sites. The differences among these three sites were rationalized in terms of the molecular and electronic structures of the reactive complexes along the reaction pathway. The explicit solvation effect was estimated through the similar abstraction of a zwitterionic glycine with the combination of microsolvation and a CPCM model. Our results indicate that the α-H abstraction at certain sites requires explicit salvation to obtain accurate results. A replica exchange molecular dynamics simulation was performed to demonstrate the structural change due to this type of abstraction.

Variation of reaction dynamics for OH hydrogen abstraction from glycine between ab initio levels of theory.

The variation in reaction dynamics of OH hydrogen abstraction from glycine between HF, MP2, CCSD(T), M05-2X, BHandHLYP, and B3LYP levels was demonstrated. The abstraction mode shows distinct patterns between these five levels and determines the barrier height, and the spin density transfer between OH radical and glycine. These differences are mainly resulted from the spin density distribution and geometry of the alpha carbon during the abstraction. The captodative effect which is commonly believed as one of the major factors to stabilize the caron-centered radical can only be observed in DFT levels but not in HF and MP2 levels. Difference in the abstraction energy were found in these calculation levels, by using the result of CCSD(T) as reference, B3LYP, BHandHLYP, and M05-2X underestimated the reaction barrier about 5.1, 0.1, and 2.4 kcal mol(-1), while HF and MP2 overestimated 19.1 kcal mol(-1) and 1.6 kcal mol(-1), respectively. These differences can be characterized by the vibration mode of imaginary frequency of transition states, which indicates the topology around transition states and determines reaction barrier height. In this model system, BHandHLYP provides the best prediction of the energy barrier among those tested methods.

Site specificity of the (alpha)C--H bond dissociation energy for a naturally occurring beta-hairpin peptide-An ab initio study.

A naturally occurring beta-hairpin peptide (PDB ID 1UAO) was used as a model to study the backbone oxidation of a protein with ab initio calculation at the B3LYB/6-31G(d) without any constraints. The (alpha)C--H bond dissociation energy of three different glycyl radicals located at different sites on the beta-hairpin peptide was calculated to evaluate the site specificity of backbone oxidation. The molecular and electronic structures of these glycyl radicals were analyzed to rationalize this site specificity. The overall molecular structure of the alpha-H abstracted beta-hairpin peptide remained almost unchanged with the exception of the local conformation of the attacked residue. However, the (alpha)C--H bond strength varied dramatically among these different sites.

Asymmetric synthesis of alpha,alpha-disubstituted alpha-amino acids by diastereoselective alkylation of camphor-based tricyclic iminolactone.

A novel and convenient route for the preparation of chiral tricyclic iminolactones 9 and 10 from camphorquinone has been developed. Alkylation of iminolactones 9 and 10 provided iminolactones 16 and 17 in high yields which were, in turn, alkylated again to afford the alpha,alpha-disubstituted products in good yields (70-90%) and excellent diastereoselectivities (>98%). Hydrolysis of the alkylated iminolactones furnished the desired alpha,alpha-disubstituted alpha-amino acids in good yields and high enantiomeric excesses with good recovery yields of the chiral auxiliary 12 and 13. The extremely high endo-face selectivity for alkylation is discussed using semiempirical (MOPAC 93) calculations.

Porphyrin dimers bridged by a platinum-diacetylide unit.

A series of butadiyne- and platinum diacetylide-bridged conjugated porphyrin dimers have been prepared; electrochemical and UV-vis absorption measurements on these compounds show that the butadiyne-bridge confers stronger porphyrin-porphyrin conjugation than the platinum diacetylide-bridge.