术后腹腔化疗对老年结直肠癌患者生存质量的影响

目的评价老年结直肠癌患者手术后腹腔化疗对生存质量的影响。方法调查1998年1月至2002年12月期间52例60岁以上进行术后腹腔化疗的患者的生存质量GLQI指数,并与同期、同年龄段44例静脉化疗患者和40名健康老年对照组进行比较。所有病人于术前和术后6个月期间调查患者的生存质量。结果老年结直肠癌患者手术前的生存质量GLQI指数明显低于正常老年人群(P<0.05)。而两组患者手术前的生存质量GLQI指数无显著差异(P>0.05)。腹腔化疗组患者手术后6个月期间的生存质量GLQI指数高于静脉化疗组患者,其差异存在统计学意义(P<0.05)。腹腔化疗组患者手术后3月、4月、5月和6月的生存质量GLQI指数与正常老年人群无显著差异(P>0.05);而静脉化疗组患者手术后3月、4月、5月和6月的生存质量GLQI指数仍低于正常老年人群(P<0.05)。结论针对老年结直肠癌患者的生理特点,手术后采用腹腔化疗,不仅有利于提高手术后的生存期;而且有助于提高患者的生存质量,是老年结直肠癌患者手术后首选的理想化疗方式。     

Purinosome formation as a function of the cell cycle

The de novo purine biosynthetic pathway relies on six enzymes to catalyze the conversion of phosphoribosylpyrophosphate to inosine 5′-monophosphate. Under purine-depleted conditions, these enzymes form a multienzyme complex known as the purinosome. Previous studies have revealed the spatial organization and importance of the purinosome within mammalian cancer cells. In this study, time-lapse fluorescence microscopy was used to investigate the cell cycle dependency on purinosome formation in two cell models. Results in HeLa cells under purine-depleted conditions demonstrated a significantly higher number of cells with purinosomes in the G₁ phase, which was further confirmed by cell synchronization. HGPRT-deficient fibroblast cells also exhibited the greatest purinosome formation in the G₁ phase; however, elevated levels of purinosomes were also observed in the S and G₂/M phases. The observed variation in cell cycle-dependent purinosome formation between the two cell models tested can be attributed to differences in purine biosynthetic mechanisms. Our results demonstrate that purinosome formation is closely related to the cell cycle.Enzymes have been shown to form clusters in a cell to regulate metabolic processes (1–3). More recently, the concept of multienzyme complexes has been expanded to include mesoscale protein assemblies that appear to be substantially larger than a single protein (4). Depending on the metabolic or developmental state of the cells, these types of protein clusters range from transiently associated to very rigid and well defined (4). Examples of such enzyme clusters include the EF-Tu cytoskeleton, RNA degradosome, CTP synthase, carboxysomes, and nucleolus (5–9).In humans, purine nucleotides are synthesized by two different mechanisms. The first mechanism, de novo purine biosynthesis, converts phosphoribosylpyrophosphate (PRPP) to inosine 5′-phosphate (IMP) in 10 highly conserved steps catalyzed by six enzymes. These six enzymes include one trifunctional enzyme (TrifGART: GARS, GART, and AIRS domains), two bifunctional enzymes (PAICS: CAIRS and SAICARS domains; ATIC: AICART and IMPCH domains), and three monofunctional enzymes (PPAT, FGAMS, and ASL). ASL is also necessary for the conversion of IMP to AMP and may be classified as bifunctional (10). The second mechanism uses nucleotide salvage pathways to either phosphorylate a nucleoside (e.g., thymidine kinase) or add a purine base to ribose 5′-phosphate to regenerate the respective monophosphate. For example, hypoxanthine/guanine phosphoribosyl transferase (HGPRT) catalyzes the conversion of hypoxanthine to IMP and the conversion of guanine to guanosine 5′-phosphate (GMP). The de novo pathway is more energy-intensive, with the synthesis of 1 mole of IMP requiring 5 moles of ATP. Therefore, the salvage pathway is the preferred pathway for purine biosynthesis. Cells deficient in HGPRT, such as those that exhibit a Lesch–Nyhan disease (LND) phenotype, rely primarily on the de novo purine biosynthetic pathway to generate purine nucleotides (11–15).Recently, enzymes in the de novo purine biosynthetic pathway were shown to organize and reversibly assemble into punctate cellular bodies known as “purinosomes” under purine-depleted conditions (16). Further investigations into the organization of the purinosome showed that several of the enzymes form a core structure (PPAT, TrifGART, and FGAMS), whereas others appear to interact peripherally (PAICS, ASL, and ATIC) (17). The presence of this protein assembly and its putative function(s) clearly suggest that the spatial organization of pathway enzymes into purinosomes within a cell play an important role in meeting the cellular demand for purines (18). Although many studies have implied up-regulation of the de novo purine biosynthetic pathway during cell cycle progression (14, 19–21), here we used time-lapse microscopy to determine whether a correlation exists between the cell cycle stage and the number of cells with purinosomes or the cells’ purinosome content. Two different cell types, HeLa and LND cells, were used, with the latter deficient in purine salvage, to assess the effect of increased demand on the de novo pathway for purine biosynthesis and the attendant consequences for purinosome assembly.     

Dual roles of an Arabidopsis ESCRT component FREE1 in regulating vacuolar protein transport and autophagic degradation

Protein turnover can be achieved via the lysosome/vacuole and the autophagic degradation pathways. Evidence has accumulated revealing that efficient autophagic degradation requires functional endosomal sorting complex required for transport (ESCRT) machinery. However, the interplay between the ESCRT machinery and the autophagy regulator remains unclear. Here, we show that FYVE domain protein required for endosomal sorting 1 (FREE1), a recently identified plant-specific ESCRT component essential for multivesicular body (MVB) biogenesis and plant growth, plays roles both in vacuolar protein transport and autophagic degradation. FREE1 also regulates vacuole biogenesis in both seeds and vegetative cells of Arabidopsis. Additionally, FREE1 interacts directly with a unique plant autophagy regulator SH3 DOMAIN-CONTAINING PROTEIN2 and associates with the PI3K complex, to regulate the autophagic degradation in plants. Thus, FREE1 plays multiple functional roles in vacuolar protein trafficking and organelle biogenesis as well as in autophagic degradation via a previously unidentified regulatory mechanism of cross-talk between the ESCRT machinery and autophagy process.The endosomal–lysosomal/vacuolar pathway is the primary catabolic system of eukaryotic cells that degrades extracellular and intracellular materials. Membrane proteins destined for degradation, such as misfolded proteins or endocytosed receptors, become tagged by ubiquitin for further sorting to the endosomal–lysosomal/vacuolar system for degradation (1). During this process, an evolutionarily conserved machinery called endosomal sorting complex required for transport (ESCRT), is responsible for sorting these ubiquitinated cargos into the intraluminal vesicles (ILVs) of prevacuolar compartments/multivesicular bodies (PVCs/MVBs), which subsequently fuse with vacuoles/lysosomes to deliver their contents into the lumen for proteolytic degradation (2, 3). Malfunction of the assembly or dissociation of the ESCRT machinery disrupts MVB formation and thus results in the accumulation of ubiquitinated membrane cargos (4, 5).Macroautophagy (hereafter as autophagy) is another highly conserved catabolic process, which converges on the endosomal–lysosomal/vacuolar pathway to deliver aberrant organelles, long-lived proteins, and protein aggregates to the lysosome/vacuole via a unique structure termed the “autophagosome” (6). Morphologically different from MVBs, autophagosomes are characterized by a double membrane structure, which is initiated from the phagophore assembly site/preautophagosome site (PAS) (7). The proteins or organelles to be degraded are encapsulated by autophagosomes that fuse either directly with the vacuole/lysosome or with endosomes like MVBs for expansion/maturation to form amphisomes, which then fuse with vacuole/lysosome for degradation. A number of conserved autophagy-related gene (ATG) proteins have been identified as participating in the autophagy pathway in eukaryotic cells (8).Even though it is generally accepted that at least one population of developing autophagosomes fuses with late endosomal compartments before their fusion with lysosomes, little is known about the functional relationship between the autophagy and endocytic pathways. New light has been thrown onto this situation through the discovery that ESCRT is also involved in autophagy. More and more studies on nematodes, flies, mammals, and even on plants provide evidence to support the conclusion that the inactivation of ESCRT machinery causes an accumulation of autophagosomes (9–13). Different models, such as the induction of autophagy or the disruption of autophagosome–endosome/lysosome fusion, have been proposed to explain the observation that autophagosomes accumulate in ESCRT-depleted cells (14, 15). However, there are no studies to give a direct link between ESCRT machinery and autophagy regulators.Here, we show that FYVE domain protein required for endosomal sorting 1 (FREE1), which represents a recently identified and unique plant ESCRT component essential for MVB biogenesis (5), plays a crucial role in vacuolar protein transport and vacuole biogenesis. In addition, FREE1 directly interacts with SH3 DOMAIN-CONTAINING PROTEIN2 (SH3P2), a unique regulator in plant autophagy (16), to manipulate the autophagosome–vacuole fusion and finally autophagic degradation in plants. Our studies have thus unveiled a previously unidentified regulatory mechanism for direct cross-talk between the ESCRT machinery and autophagy process.     

Implausibility of the vibrational theory of olfaction

The vibrational theory of olfaction assumes that electron transfer occurs across odorants at the active sites of odorant receptors (ORs), serving as a sensitive measure of odorant vibrational frequencies, ultimately leading to olfactory perception. A previous study reported that human subjects differentiated hydrogen/deuterium isotopomers (isomers with isotopic atoms) of the musk compound cyclopentadecanone as evidence supporting the theory. Here, we find no evidence for such differentiation at the molecular level. In fact, we find that the human musk-recognizing receptor, OR5AN1, identified using a heterologous OR expression system and robustly responding to cyclopentadecanone and muscone, fails to distinguish isotopomers of these compounds in vitro. Furthermore, the mouse (methylthio)methanethiol-recognizing receptor, MOR244-3, as well as other selected human and mouse ORs, responded similarly to normal, deuterated, and ¹³C isotopomers of their respective ligands, paralleling our results with the musk receptor OR5AN1. These findings suggest that the proposed vibration theory does not apply to the human musk receptor OR5AN1, mouse thiol receptor MOR244-3, or other ORs examined. Also, contrary to the vibration theory predictions, muscone-d₃₀ lacks the 1,380- to 1,550-cm⁻¹ IR bands claimed to be essential for musk odor. Furthermore, our theoretical analysis shows that the proposed electron transfer mechanism of the vibrational frequencies of odorants could be easily suppressed by quantum effects of nonodorant molecular vibrational modes. These and other concerns about electron transfer at ORs, together with our extensive experimental data, argue against the plausibility of the vibration theory.In 1870, the British physician William Ogle wrote: “As in the eye and the ear the sensory impression is known to result not from the contact of material particles given off by the object seen or heard, but from waves or undulations of the ether or the air, one cannot but suspect that the same may be true in the remaining sense, and that the undulatory theory of smell… [may be] the true one” (1, 2). Of the 29 different “theories of odour” listed in the 1967 edition of The Chemical Senses (3), nine associate odor with vibrations, particularly those theories championed by Dyson (4, 5) and Wright (6–8). However, the premise that olfaction involves detection of vibrational frequencies of odorants remains highly speculative because neither the structures of the odorant receptors (ORs) nor the binding sites or the activation mechanisms triggered upon odorant binding to ORs have been established. In 1996–1997, Turin (9–12) elaborated on the undulatory theory of smell, as considered in more detail below, and suggested that a mechanism analogous to inelastic electron tunneling spectroscopy (13) may be involved, where tunneling electrons in the receptor probe the vibrational frequencies of odorants. In 2013, Gane et al. (14) commented that “whether olfaction recognizes odorants by their shape, their molecular vibrations, or both remains an open and controversial question” and that “a convenient way to address [this question] is to test for odor character differences between deuterated and nondeuterated odorant isotopomers since these have identical ground-state conformations but different vibrational modes.” Gane et al. (14) also stated that a particularly appropriate test case would involve odorants containing “more CH group… [such as] musks [which] are among the largest odorants and typically contain 15–18 carbons and 28 or more hydrogens.”In judging the plausibility of the vibration theory, we use a multipronged approach:

• i)We consider the concepts of shape vs. vibration theory and odorant perception vs. reception.
• ii)As a test of the vibration theory, we have prepared a series of isotopomers of musks and other compounds, containing up to 30 C–H or C–D bonds as test odorants, which are evaluated using in vitro activation of receptors identified by us and other groups as being highly responsive to these isotopomers.
• iii)We consider the confounding effects of impurities and isotope effects in interpreting odorant perception, as well as the validity of requirements for specific IR bands for recognition of musks by their receptors.
• iv)We examine the physical validity of the models developed to support the vibration theory.
• v)We consider the specific limitations of our in vitro approach using isotopomers to evaluate the vibration theory, based primarily on results obtained with a single identified human musk OR, in addition to other OR/ligand pairs.
• vi)We consider plausible nonvibration theory models for docking of musks to the human musk receptor, OR5AN1, where the musk carbonyl group functions as a hydrogen bond acceptor.

Gane et al. (14) have framed the argument for olfactory discrimination of hydrogen isotopomers as one of “shape” vs. “vibration.” However, neither the binding modes of isotopomers nor their activation mechanisms are known. ORs belong to the superfamily of class A G protein-coupled receptors (GPCRs), which are known to be activated through allosteric conformational changes induced upon ligand binding even without triggering any kind of electron transfer processes. Ligand–receptor interactions can be both attractive and repulsive, involving hydrogen bonding, van der Waals, cation–π, π–π, ion–ion, dipole–dipole, steric, and hydrophobic interactions with the receptor, with water channels and bridging water molecules mediating hydrogen bonds, as well as metal–ion coordination, as we have recently demonstrated in the latter case (15, 16). Therefore, molecular shape can be considered a “straw-man” alternative to the vibration theory when describing the differing affinities of ligands bound to GPCRs (17, 18), including isotopomers (19, 20). Some of these attractive and repulsive interactions were identified in 1940 by Pauling and Delbrück (21), who note that interacting biomolecules “must have complementary surfaces, like die and coin, and also a complementary distribution of active groups.” In addition, shape-related features are misrepresented by vibration theory proponents. For example, Franco et al. (17) stated: “Given that proteins are chiral, a shape-only theory cannot account for the identical odors of most enantiomeric pairs,” echoing similar comments by Turin (22): “One would therefore generally expect enantiomers to have completely different smells. This is emphatically not the case.” However, these assertions are clearly at odds with the highly developed ability of mice and other mammals to discriminate an array of nonpheromonal chiral odorant enantiomeric pairs (23–25), with the divergent in vitro responses to enantiomers by different combinations of ORs (26) and, in particular, with the highly selective response of the musk-sensitive mouse receptor, MOR215-1, to (R)-muscone (“l-muscone”) compared with (S)-muscone (“d-muscone”) (27).In addition to our concerns regarding shape, a second issue relates to describing how different smells are perceived, that is, the perception of an odorant. It is known that in vivo perception of odorants reflects the totality of perireceptor events as well as odorant–OR interactions (reception). Volatile odorants enter the nasal passage, where they dissolve in the nasal mucus overlying the olfactory epithelium and are then rapidly detected by ORs on the cilia of the olfactory sensory neurons, ultimately leading to signaling (28, 29). It is the mechanism of odorant–OR interactions, the reception of the odorant, that we seek to examine with isotopomers to determine whether the vibration theory is plausible, displaying isotope effects, because perception could be influenced by isotope effects due to the perireceptor events involving mucosal components, such as enzymes, mucopolysaccharides, salts, and antibodies.Whether deuterated and nondeuterated odorant isotopomers can be distinguished by smell and, even if they can, whether this distinction validates the vibration theory is a matter of contention. A 2001 paper by Haffenden et al. (30) reported that benzaldehyde-d₆ gave a statistically significant difference in odor perception relative to normal benzaldehyde, in support of the vibration theory. However, this study has been criticized for lacking double-blind controls to eliminate bias and because it used an anomalous version of the duo-trio test (31). Furthermore, the study failed to account for perireceptor events, namely, the enzyme-mediated conversion of odorants that has been shown to occur in nasal mucus. For example, benzaldehyde is converted to benzoic acid (32), a reaction potentially subject to significant primary isotope effects (2, 33, 34), which could explain the difference in odor perception for the benzaldehyde isotopomers. Earlier claims that human subjects can distinguish odors of acetophenone isotopomers (9, 35) have been shown to be untrue (14, 31). Recent studies indicate that Drosophila melanogaster can distinguish acetophenone isotopomers (36, 37) and that Apis mellifera L., the honey bee, can be trained to discriminate pairs of isotopomers (38). These studies differ from earlier insect studies in which isotopomer discrimination was not found. For example, systematic deuteration of 4-(p-hydroxyphenyl)-2-butanone acetate, a Dacus cucurbitae Coquillett (the male melon fly) attractant, did not affect the attractiveness of the compound to the fly (39); deuteration of alarm pheromones failed to alter the response toward these compounds by Pogonomyrmex badius worker ants (40); and honey bees could not distinguish between deuterated and nondeuterated nitrobenzene (41).Concerns have been raised (42) about aspects of the Drosophila study (36), which is “behavioural and not at the receptor level” (2) (also a concern with the Apis study). Also, given that the ORs and their downstream signaling in Drosophila and humans are completely unrelated, the Drosophila study should not be considered predictive of the ability of humans to distinguish isotopomers (2, 17). In view of the above discussion, it is interesting that in a blinded behavioral study, smell panelists distinguished between deuterated and nondeuterated isotopomers of cyclopentadecanone (1; Fig. 1A) and other musk odorants (14).Open in a separate windowFig. 1.(A) Preparation of deuterated 1–3. Deuterium could be selectively introduced, or selectively removed, adjacent to the carbonyl group using D₂O/K₂CO₃ or H₂O/K₂CO₃, respectively, at 130 °C; global replacement of all hydrogens could be achieved with Rh/C in D₂O at 150 °C. Repetition led to more complete deuteration as well as reduction of 1 to 3 and 2; oxidation of 2 gave 1 with ∼98% deuteration. Chromatography of deuterated 1 with freshly distilled pentane followed by repeated recrystallization from methanol/water to constant melting point gave samples showing no new peaks in their ¹H NMR spectra, other than very weak peaks corresponding to those peaks seen in undeuterated 1. (B) Deuterated (97%) muscone 4 was prepared via alcohol 5 as above. (C) 8-d₅ and 2,4,5,7-tetrathiaoctane-d_10, (9-d₁₀; 98% deuterium) were prepared as shown. Details of these syntheses are provided in SI Appendix.Here, we study the response of human musk-sensitive OR5AN1, identified through screening of heterologously expressed human ORs, to cyclopentadecanone (1) and muscone (4) isotopomers. We also present pharmacological data on the response of mouse ORs to deuterated and nondeuterated acetophenone and benzaldehyde, as well as selected ¹³C isotopomers. In addition, we present related studies on the response of various human and mouse ORs to other deuterated and nondeuterated odorants, including (methylthio)-methanethiol (MTMT, 8; Fig. 1C) and bis(methylthiomethyl) disulfide (9), studied in connection with our investigation of the role of copper coordination in the recognition of both sulfur-containing odorants by the mouse (methylthio)methanethiol receptor, MOR244-3 (15, 16). Insofar as the ability to distinguish odors of isotopomers directly tests the predictions of the vibration theory, the comparative response of human and mouse ORs to isotopomers of these selected ligands in the heterologous OR expression system constitutes a robust test of the vibration theory. Finally, we discuss the basis for recent vibration theories of olfaction and supporting computational evidence (37, 43–47) in light of well-established electron transfer theories (48). We point out that key assumptions underlying the vibration theory lack experimental support and are missing important physical features expected for biological systems.     

XRCC3 is a promising target to improve the radiotherapy effect of esophageal squamous cell carcinoma

Radiotherapy is widely applied for treatment of esophageal squamous cell carcinoma (ESCC). The Rad51‐related protein XRCC3 plays roles in the recombinational repair of DNA double‐strand breaks to maintain chromosome stability and repair DNA damage. The present study aimed to investigate the effect of XRCC3 on the radiotherapy response of ESCC and the underlying mechanisms of the roles of XRCC3 in ESCC radiosensitivity. XRCC3 expression in ESCC cells and tissues was higher than that in normal esophageal epithelial cells and corresponding adjacent noncancerous esophageal tissue. High XRCC3 expression was positively correlated with resistance to chemoradiotherapy in ESCC and an independent predictor for short disease‐specific survival of ESCC patients. Furthermore, the therapeutic efficacy of radiotherapy in vitro and in vivo was substantially increased by knockdown of XRCC3 in ESCC cells. Ectopic overexpression of XRCC3 in both XRCC3‐silenced ESCC cells dramatically enhanced ESCC cells' resistance to radiotherapy. Moreover, radiation resistance conferred by XRCC3 was attributed to enhancement of homologous recombination, maintenance of telomere stability, and a reduction of ESCC cell death by radiation‐induced apoptosis and mitotic catastrophe. Our data suggest that XRCC3 protects ESCC cells from ionizing radiation‐induced death by promoting DNA damage repair and/or enhancing telomere stability. XRCC3 may be a novel radiosensitivity predictor and promising therapeutic target for ESCC.     

Potential therapeutic target for malignant paragangliomas: ATP synthase on the surface of paraganglioma cells

F1FoATP synthase (ATP synthase) is a ubiquitous enzyme complex in eukaryotes. In general it is localized to the mitochondrial inner membrane and serves as the last step in the mitochondrial oxidative phosphorylation of ADP to ATP, utilizing a proton gradient across the inner mitochondrial membrane built by the complexes of the electron transfer chain. However some cell types, including tumors, carry ATP synthase on the cell surface. It was suggested that cell surface ATP synthase helps tumor cells thriving on glycolysis to survive their high acid generation. Angiostatin, aurovertin, resveratrol, and antibodies against the α and β subunits of ATP synthase were shown to bind and selectively inhibit cell surface ATP synthase, promoting tumor cell death. Here we show that ATP synthase β (ATP5B) is present on the cell surface of mouse pheochromocytoma cells as well as tumor cells of human SDHB-derived paragangliomas (PGLs), while being virtually absent on chromaffin primary cells from bovine adrenal medulla by confocal microscopy. The cell surface location of ATP5B was verified in the tissue of an SDHB-derived PGL by immunoelectron microscopy. Treatment of mouse pheochromocytoma cells with resveratrol as well as ATP5B antibody led to statistically significant proliferation inhibition. Our data suggest that PGLs carry ATP synthase on their surface that promotes cell survival or proliferation. Thus, cell surface ATP synthase may present a novel therapeutic target in treating metastatic or inoperable PGLs.