Cystine addiction of triple-negative breast cancer associated with EMT augmented death signaling.

This corrects the article DOI: 10.1038/onc.2016.394.

Cystine addiction of triple-negative breast cancer associated with EMT augmented death signaling.

Despite the advances in the diagnosis and treatment of breast cancer, breast cancers still cause significant mortality. For some patients, especially those with triple-negative breast cancer, current treatments continue to be limited and ineffective. Therefore, there remains an unmet need for a novel therapeutic approach. One potential strategy is to target the altered metabolic state that is rewired by oncogenic transformation. Specifically, this rewiring may render certain outside nutrients indispensable. To identify such a nutrient, we performed a nutrigenetic screen by removing individual amino acids to identify possible addictions across a panel of breast cancer cells. This screen revealed that cystine deprivation triggered rapid programmed necrosis, but not apoptosis, in the basal-type breast cancer cells mostly seen in TNBC tumors. In contrast, luminal-type breast cancer cells are cystine-independent and exhibit little death during cystine deprivation. The cystine addiction phenotype is associated with a higher level of cystine-deprivation signatures noted in the basal type breast cancer cells and tumors. We found that the cystine-addicted breast cancer cells and tumors have strong activation of TNFα and MEKK4-p38-Noxa pathways that render them susceptible to cystine deprivation-induced necrosis. Consistent with this model, silencing of TNFα and MEKK4 dramatically reduces cystine-deprived death. In addition, the cystine addiction phenotype can be abrogated in the cystine-addictive cells by miR-200c, which converts the mesenchymal-like cells to adopt epithelial features. Conversely, the introduction of inducers of epithelial-mesenchymal transition (EMT) in cystine-independent breast cancer cells conferred the cystine-addiction phenotype by modulating the signaling components of cystine addiction. Together, our data reveal that cystine-addiction is associated with EMT in breast cancer during tumor progression. These findings provide the genetic and mechanistic basis to explain how cystine deprivation triggers necrosis by activating pre-existing oncogenic pathways in cystine-addicted TNBC with prominent mesenchymal features.

Metabolism of phenolic compounds during loquat fruit development.

Phenolic compounds in loquat fruit were identified as 5-caffeoylquinic acid (chlorogenic acid), neochlorogenic acid, hydroxybenzoic acid, 5-p-feruloylquinic acid, protocatechuic acid, 4-caffeoylquinic acid, epicatechin, o-coumaric acid, ferulic acid, and p-coumaric acid. Neochlorogenic acid was found to be dominant in the early stages of loquat fruit development. Both the concentrations and types of phenolic compounds were high in young fruit but then decreased steadily during growth. However, the concentration of chlorogenic acid increased during ripening and became predominant in ripe fruit. The large rise in chlorogenic acid concentration appears to be a characteristic of loquat fruit ripening. In all of the cultivars tested, the types of phenolic compounds were similar but the total phenolic content varied from 81.8 to 173.8 mg/100 g of fresh pulp. In the biosynthetic pathway of chlorogenic acid, the enzyme activities of phenylalanine ammonia-lyase (PAL), 4-coumarate:CoA ligase (CL), and hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (CQT) were high at the early stage of growth, diminished to low levels approximately 3 weeks prior to harvest, but then rose to a peak at 1 week before harvest. The changes of these enzyme activities seemed to be associated with variations in chlorogenic acid concentration during development, maturation, and ripening of loquat fruit.

Comparison of UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene sequences between white grapes (Vitis vinifera) and their sports with red skin.

The expression of the UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene has been shown to be critical for anthocyanin biosynthesis in the grape berry. Using white cultivars and bud sports with red skin, we examined the expression of seven anthocyanin biosynthetic genes including the UFGT gene and compared the coding/promoter sequences of the UFGT gene. Northern blot analysis showed that the seven anthocyanin biosynthetic genes were expressed coordinately at higher levels in the red-skin sports than in the white-skin progenitors of the sports. It was especially notable that UFGT gene expression was detected only in the red-skin sports and Kyoho. However, there were no differences in either coding or promoter sequences between Italia (Vitis vinifera) and its red-skin sport Ruby Okuyama, or between Muscat of Alexandria (V. vinifera) and the red-skin sport Flame Muscat. From these findings, the phenotypic change from white to red in the sports is thought to be the result of a mutation in a regulatory gene controlling the expression of UFGT.

Kiwifruits (Actinidia deliciosa) transformed with a Vitis stilbene synthase gene produce piceid (resveratrol-glucoside).

A stilbene synthase gene was isolated from three Vitis spp. (V. vinifera, V. labrusca and V. riparia). These genes were placed under the control of the cauliflower mosaic virus 35S promoter and introduced into kiwifruit (Actinidia deliciosa) plants by Agrobacterium-mediated gene transfer. The introduced gene(s) were expressed and piceid (resveratrol-glucoside) rather than resveratrol was produced in the leaves of the transformants. Resveratrol produced by the action of the integrated gene(s) seems to be metabolized into piceid by an endogenous glycosyltransferase. Among the transformants obtained, the highest piceid content in the young leaves was 182 µg/g fresh weight. Although these transformants did not show resistance against Botrytis cinerea, which causes gray-mould disease, the fruits may have some beneficial effects on human health.

Identification and inhibition of the ICE/CED-3 protease necessary for mammalian apoptosis.

The protease responsible for the cleavage of poly(ADP-ribose) polymerase and necessary for apoptosis has been purified and characterized. This enzyme, named apopain, is composed of two subunits of relative molecular mass (M(r)) 17K and 12K that are derived from a common proenzyme identified as CPP32. This proenzyme is related to interleukin-1 beta-converting enzyme (ICE) and CED-3, the product of a gene required for programmed cell death in Caenorhabditis elegans. A potent peptide aldehyde inhibitor has been developed and shown to prevent apoptotic events in vitro, suggesting that apopain/CPP32 is important for the initiation of apoptotic cell death.