Experimental documentation of natural hybridization inCactaceae: Origin of Lloyd's Hedgehog Cactus,Echinocereus ×lloydii

The origin ofEchinocereus ×lloydii Britt. & Rose, pro sp. (Lloyd's Hedgehog Cactus) was investigated using comparative morphology, cytology, biochemistry, and particularly, artificial hybridization. Numerous artificial crosses between the putative parentsE. coccineus Engelm. (a species of claret-up cactus) andE. dasyacanthus Engelm. (Texas Rainbow Cactus) were successful, resulting in the production of hundreds of seeds with hybrid embryos. The F₁ hybrid progeny (i.e., syntheticE. ×lloydii) grew to sexual maturity in about four and one-half years, whereupon successful backcrosses and F₂ generation hybrids were also obtained. The known F₁ hybrids closely approximated naturalE. ×lloydii. The fertility of these syntheticE. ×lloydii was high, like their natural counterparts. The populations ofE. ×lloydii in Pecos County, Texas are inferred to have originated as the result of natural interspecific hybridization. It is assumed thatE. ×lloydii or similar plants may arise wherever the parental taxa grow sympatrically.     

Methylated DNA/RNA in Body Fluids as Biomarkers for Lung Cancer

DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer.     

Biodeterioration of Mayan buildings at uxmal and tulum,Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.     

Hsp27-induced MMP-9 expression is influenced by the Src tyrosine protein kinase yes

The small heat shock protein hsp27 is associated with aggressive tumor behavior in certain subsets of breast cancer patients. Previously we demonstrated that hsp27 overexpression in breast cancer cells increased in vitro and in vivo invasiveness, suggesting that hsp27 influences the metastatic process. To investigate this role for hsp27, we have utilized MDA-MB-231 breast cancer cells that overexpress hsp27 and cDNA expression array technology. We demonstrate that hsp27 overexpression up-regulates MMP-9 expression and activity and down-regulates Yes expression. Furthermore, our results suggest that Yes may be involved in regulating MMP-9 expression, as well as in vitro invasion. Reconstitution of Yes expression by transfection into hsp27-overexpressing cells decreased MMP-9 expression, and increased in vitro invasiveness, abrogating the phenotype conferred by hsp27 overexpression. Therefore, our results provide a new potential mechanism by which hsp27 affects the metastatic cascade-through regulation of MMP-9 and Yes expression.     

Crystal structures of pinoresinol-lariciresinol and phenylcoumaran benzylic ether reductases and their relationship to isoflavone reductases

Despite the importance of plant lignans and isoflavonoids in human health protection (e.g. for both treatment and prevention of onset of various cancers) as well as in plant biology (e.g. in defense functions and in heartwood development), systematic studies on the enzymes involved in their biosynthesis have only recently begun. In this investigation, three NADPH-dependent aromatic alcohol reductases were comprehensively studied, namely pinoresinol-lariciresinol reductase (PLR), phenylcoumaran benzylic ether reductase (PCBER), and isoflavone reductase (IFR), which are involved in central steps to the various important bioactive lignans and isoflavonoids. Of particular interest was in determining how differing regio- and enantiospecificities are achieved with the different enzymes, despite each apparently going through similar enone intermediates. Initially, the three-dimensional x-ray crystal structures of both PLR_Tp1 and PCBER_Pt1 were solved and refined to 2.5 and 2.2 A resolutions, respectively. Not only do they share high gene sequence similarity, but their structures are similar, having a continuous alpha/beta NADPH-binding domain and a smaller substrate-binding domain. IFR (whose crystal structure is not yet obtained) was also compared (modeled) with PLR and PCBER and was deduced to have the same overall basic structure. The basis for the distinct enantio-specific and regio-specific reactions of PCBER, PLR, and IFR, as well as the reaction mechanism and participating residues involved (as identified by site-directed mutagenesis), are discussed.     

Constitutive activation of smoothened (SMO) in mammary glands of transgenic mice leads to increased proliferation, altered differentiation and ductal dysplasia

The hedgehog signaling network regulates pattern formation, proliferation, cell fate and stem/progenitor cell self-renewal in many organs. Altered hedgehog signaling is implicated in 20-25% of all cancers, including breast cancer. We demonstrated previously that heterozygous disruption of the gene encoding the patched-1 (PTCH1) hedgehog receptor, a negative regulator of smoothened (Smo) in the absence of ligand, led to mammary ductal dysplasia in virgin mice. We now show that expression of activated human SMO (SmoM2) under the mouse mammary tumor virus (MMTV) promoter in transgenic mice leads to increased proliferation, altered differentiation, and ductal dysplasias distinct from those caused by Ptch1 heterozygosity. SMO activation also increased the mammosphere-forming efficiency of primary mammary epithelial cells. However, limiting-dilution transplantation showed a decrease in the frequency of regenerative stem cells in MMTV-SmoM2 epithelium relative to wild type, suggesting enhanced mammosphere-forming efficiency was due to increased survival or activity of division-competent cell types under anchorage-independent growth conditions, rather than an increase in the proportion of regenerative stem cells per se. In human clinical samples, altered hedgehog signaling occurs early in breast cancer development, with PTCH1 expression reduced in approximately 50% of ductal carcinoma in situ (DCIS) and invasive breast cancers (IBC). Conversely, SMO is ectopically expressed in 70% of DCIS and 30% of IBC. Surprisingly, in both human tumors and MMTV-SmoM2 mice, SMO rarely colocalized with the Ki67 proliferation marker. Our data suggest that altered hedgehog signaling may contribute to breast cancer development by stimulating proliferation, and by increasing the pool of division-competent cells capable of anchorage-independent growth.     

Selective small molecule stat3 inhibitor reduces breast cancer tumor-initiating cells and improves recurrence free survival in a human-xenograft model

Metastasis and disease relapse are hypothesized to result from tumor initiating cells (TICs). Previously, we have defined a CD44+/CD24-/low mammosphere-forming tumorigenic 493-gene signature in breast cancer. Stat3 was identified as a critical node in self-renewal based on an ongoing lentiviral shRNA screen being conducted in two breast cancer cell lines SUM159 and BT549. In corroborating work, targeting the SH2 domain of Stat3 with a novel small molecule decreased the percentage of cells expressing TIC markers (CD44+/CD24-/low and ALDH+) and mammosphere formation in p-Stat3 overexpressing human breast cancer xenografts in SCID-beige mice. Importantly, we observed a four-fold improvement in the 30-day recurrence-free survival relative to docetaxel alone with the addition of the Stat3 inhibitor in the chemoresistant tumor model. Thus, these findings provide a strong impetus for the development of selective Stat3 inhibitors in order to improve survival in patients with p-Stat3 overexpressing tumors.     

Krt6a-Positive Mammary Epithelial Progenitors Are Not at Increased Vulnerability to Tumorigenesis Initiated by ErbB2

While most breast cancers are thought to arise from the luminal layer of the breast tissue, it remains unclear which specific cells in the luminal layer are the cells of origin of breast cancer. We have previously reported that WAP-positive luminal epithelial cells are at increased susceptibility to tumor initiation by ErbB2 compared to the bulk population, while the mammary cells with canonical Wnt signaling activity fail to evolve into tumors upon ErbB2 activation. Here, we used retrovirus to introduce ErbB2 into the Krt6a-positive mammary progenitor subset of the luminal epithelium and, for comparison, into the mammary luminal epithelium indiscriminately. Tumors developed from both groups of cells with a similar latency. These data indicate that the Krt6a-positive subset of mammary epithelial cells can be induced to form cancer by ErbB2 but it is not more susceptible to tumorigenesis initiated by ErbB2 than the bulk population of the luminal epithelium.     

Terrigenous sediment-dominated reef platform infilling: an unexpected precursor to reef island formation and a test of the reef platform size–island age model in the Pacific

Low-lying coral reef islands are considered highly vulnerable to climate change, necessitating an improved understanding of when and why they form, and how the timing of formation varies within and among regions. Several testable models have been proposed that explain inter-regional variability as a function of sea-level history and, more recently, a reef platform size model has been proposed from the Maldives (central Indian Ocean) to explain intra-regional (intra-atoll) variability. Here we present chronostratigraphic data from Pipon Island, northern Great Barrier Reef (GBR), enabling us to test the applicability of existing regional island evolution models, and the platform size control hypothesis in a Pacific context. We show that reef platform infilling occurred rapidly (~4–5 mm yr⁻¹) under a “bucket-fill” type scenario. Unusually, this infilling was dominated by terrigenous sedimentation, with platform filling and subsequent reef flat formation complete by ~5000 calibrated years BP (cal BP). Reef flat exposure as sea levels slowly fell post highstand facilitated a shift towards intertidal and subaerial-dominated sedimentation. Our data suggest, however, a lag of ~1500 yr before island initiation (at ~3200 cal BP), i.e. later than that reported from smaller and more evolutionarily mature reef platforms in the region. Our data thus support: (1) the hypothesis that platform size acts to influence the timing of platform filling and subsequent island development at intra-regional scales; and (2) the hypothesis that the low wooded islands of the northern GBR conform to a model of island formation above an elevated reef flat under falling sea levels.

     

Genetic Admixture in the Culturally Unique Peranakan Chinese Population in Southeast Asia

The Peranakan Chinese are culturally unique descendants of immigrants from China who settled in the Malay Archipelago ∼300–500 years ago. Today, among large communities in Southeast Asia, the Peranakans have preserved Chinese traditions with strong influence from the local indigenous Malays. Yet, whether or to what extent genetic admixture co-occurred with the cultural mixture has been a topic of ongoing debate. We performed whole-genome sequencing (WGS) on 177 Singapore (SG) Peranakans and analyzed the data jointly with WGS data of Asian and European populations. We estimated that Peranakan Chinese inherited ∼5.62% (95% confidence interval [CI]: 4.76–6.49%) Malay ancestry, much higher than that in SG Chinese (1.08%, 0.65–1.51%), southern Chinese (0.86%, 0.50–1.23%), and northern Chinese (0.25%, 0.18–0.32%). A sex-biased admixture history, in which the Malay ancestry was contributed primarily by females, was supported by X chromosomal variants, and mitochondrial (MT) and Y haplogroups. Finally, we identified an ancient admixture event shared by Peranakan Chinese and SG Chinese ∼1,612 (95% CI: 1,345–1,923) years ago, coinciding with the settlement history of Han Chinese in southern China, apart from the recent admixture event with Malays unique to Peranakan Chinese ∼190 (159–213) years ago. These findings greatly advance our understanding of the dispersal history of Chinese and their interaction with indigenous populations in Southeast Asia.