Targeting and monitoring ovarian cancer invasion with an RNAi and peptide delivery system

RNA interference (RNAi) therapeutics are an emerging class of medicines that selectively target mRNA transcripts to silence protein production and combat disease. Despite the recent progress, a generalizable approach for monitoring the efficacy of RNAi therapeutics without invasive biopsy remains a challenge. Here, we describe the development of a self-reporting, theranostic nanoparticle that delivers siRNA to silence a protein that drives cancer progression while also monitoring the functional activity of its downstream targets. Our therapeutic target is the transcription factor SMARCE1, which was previously identified as a key driver of invasion in early-stage breast cancer. Using a doxycycline-inducible shRNA knockdown in OVCAR8 ovarian cancer cells both in vitro and in vivo, we demonstrate that SMARCE1 is a master regulator of genes encoding proinvasive proteases in a model of human ovarian cancer. We additionally map the peptide cleavage profiles of SMARCE1-regulated proteases so as to design a readout for downstream enzymatic activity. To demonstrate the therapeutic and diagnostic potential of our approach, we engineered self-assembled layer-by-layer nanoparticles that can encapsulate nucleic acid cargo and be decorated with peptide substrates that release a urinary reporter upon exposure to SMARCE1-related proteases. In an orthotopic ovarian cancer xenograft model, theranostic nanoparticles were able to knockdown SMARCE1 which was in turn reported through a reduction in protease-activated urinary reporters. These LBL nanoparticles both silence gene products by delivering siRNA and noninvasively report on downstream target activity by delivering synthetic biomarkers to sites of disease, enabling dose-finding studies as well as longitudinal assessments of efficacy.

[Ultrasonographic features and clinical pathological of liver metastasis in patients with melanoma]

Objective: To investigate the ultrasonographic features and clinical pathological of liver metastasis in patients with melanoma. Methods: Thirteen patients with liver metastasis from melanoma treated in Tianjin Medical University Cancer Institute and Hospital from 2013 to 2019 were selected, and their ultrasonographic and clinicopathological characteristics were analyzed retrospectively. Results: Eleven of the 13 patients had multiple liver lesions. The maximum diameter of the lesions was (5.89±2.73) cm. Five cases of lesions were mixed echo (3 cases with high melanin content), 4 cases of lesions were hyperechoic (3 cases with low melanin content), 3 cases of lesions were hypoechoic (all with high melanin content), 1 case of lesions were equal echo (with high melanin content). The lesions in 11 patients had clear boundaries, while other 2 patients lacked the clear borders. Cystic areas were present in the lesions of 3 patients. Six cases had irregular lesions (lobulated), and 7 cases had regular lesions (round, oval). There were acoustic halos around the lesion in 9 cases and smooth and uneven acoustic halos in 5 cases. The results of immunohistochemistry showed that 11 cases were positive for S-100, HMB45 and Melan-A. One patient was not tested for HMB45, while S-100 and Melan-A were positive. One patient did not undergo Melan-A test, while S-100 and HMB45 were positive. Conclusion: Most of the liver metastases of melanoma are mixed echo or hyperechoic, most of them are nodular with clear boundaries combined with vocal halo, and a few of the lesions have cystic areas.

Glutamine synthetase licenses APC/C-mediated mitotic progression to drive cell growth

Tumors can reprogram the functions of metabolic enzymes to fuel malignant growth; however, beyond their conventional functions, key metabolic enzymes have not been found to directly govern cell mitosis. Here, we report that glutamine synthetase (GS) promotes cell proliferation by licensing mitotic progression independently of its metabolic function. GS depletion, but not impairment of its enzymatic activity, results in mitotic arrest and multinucleation across multiple lung and liver cancer cell lines, patient-derived organoids and xenografted tumors. Mechanistically, GS directly interacts with the nuclear pore protein NUP88 to prevent its binding to CDC20. Such interaction licenses activation of the CDC20-mediated anaphase-promoting complex or cyclosome to ensure proper metaphase-to-anaphase transition. In addition, GS is overexpressed in human non-small cell lung cancer and its depletion reduces tumor growth in mice and increases the efficacy of microtubule-targeted chemotherapy. Our findings highlight a moonlighting function of GS in governing mitosis and illustrate how an essential metabolic enzyme promotes cell proliferation and tumor development, beyond its main metabolic function.

Breast tissue regeneration is driven by cell-matrix interactions coordinating multi-lineage stem cell differentiation through DDR1

Mammary morphogenesis is an orchestrated process involving differentiation, proliferation and organization of cells to form a bi-layered epithelial network of ducts and lobules embedded in stromal tissue. We have engineered a 3D biomimetic human breast that makes it possible to study how stem cell fate decisions translate to tissue-level structure and function. Using this advancement, we describe the mechanism by which breast epithelial cells build a complex three-dimensional, multi-lineage tissue by signaling through a collagen receptor. Discoidin domain receptor tyrosine kinase 1 induces stem cells to differentiate into basal cells, which in turn stimulate luminal progenitor cells via Notch signaling to differentiate and form lobules. These findings demonstrate how human breast tissue regeneration is triggered by transmission of signals from the extracellular matrix through an epithelial bilayer to coordinate structural changes that lead to formation of a complex ductal-lobular network.

Mammary morphogenesis is a complex process. Here the authors describe how stem cells build a three-dimensional self-organizing multi-lineage tissue by showing that positional signals from the extracellular matrix through the collagen receptor DDR1 lead stem cells to differentiate into multi-lineage committed multi-layered progeny.

Transcriptional Control of Metastasis by Integrated Stress Response Signaling

As a central cellular program to sense and transduce stress signals, the integrated stress response (ISR) pathway has been implicated in cancer initiation and progression. Depending on the genetic mutation landscape, cellular context, and differentiation states, there are emerging pieces of evidence showing that blockage of the ISR can selectively and effectively shift the balance of cancer cells toward apoptosis, rendering the ISR a promising target in cancer therapy. Going beyond its pro-survival functions, the ISR can also influence metastasis, especially via proteostasis-independent mechanisms. In particular, ISR can modulate metastasis via transcriptional reprogramming, in the help of essential transcription factors. In this review, we summarized the current understandings of ISR in cancer metastasis from the perspective of transcriptional regulation.

Loss of function of NF1 is a mechanism of acquired resistance to endocrine therapy in lobular breast cancer

Background

Invasive lobular carcinoma (ILC) as a disease entity distinct from invasive ductal carcinoma (IDC) has merited focused studies of the genomic landscape, but those to date are largely limited to the assessment of early-stage cancers. Given that genomic alterations develop as acquired resistance to endocrine therapy, studies on refractory ILC are needed.

Patients and methods

Tissue from 336 primary-enriched, breast-biopsied ILC and 485 estrogen receptor (ER)-positive IDC and metastatic biopsy specimens from 180 ILC and 191 ER-positive IDC patients was assayed with hybrid-capture-based comprehensive genomic profiling for short variant, indel, copy number variants, and rearrangements in up to 395 cancer-related genes.

Results

Whereas ESR1 alterations are enriched in the metastases of both ILC and IDC compared with breast specimens, NF1 alterations are enriched only in ILC metastases (mILC). NF1 alterations are predominantly under loss of heterozygosity (11/14, 79%), are mutually exclusive with ESR1 mutations [odds ratio = 0.24, P < 0.027] and are frequently polyclonal in ctDNA assays. Assessment of paired specimens shows that NF1 alterations arise in the setting of acquired resistance. An in vitro model of CDH1 mutated ER-positive breast cancer demonstrates that NF1 knockdown confers a growth advantage in the presence of 4-hydroxy tamoxifen. Our study further identified a significant increase in tumor mutational burden (TMB) in mILCs relative to breast ILCs or metastatic IDCs (8.9% >20 mutations/mb; P < 0.001). Most TMB-high mILCs harbor an APOBEC trinucleotide signature (14/16; 88%).

Conclusions

This study identifies alteration of NF1 as enriched specifically in mILC. Mutual exclusivity with ESR1 alterations, polyclonality in relapsed ctDNA, and de novo acquisition suggest a role for NF1 loss in endocrine therapy resistance. Since NF1 loss leads to RAS/RAF kinase activation, patients may benefit from a matched inhibitor. Moreover, for an independent subset of mILC, TMB was elevated relative to breast ILC, suggesting possible benefit from immune checkpoint inhibitors.

Liver cancer: WISP3 suppresses hepatocellular carcinoma progression by negative regulation of β-catenin/TCF/LEF signalling

Objectives

Wnt1‐inducible signalling pathway protein 3 (WISP3/CCN6) belongs to the CCN (CYR61/CTGF/NOV) family of proteins, dysregulation of this family contributed to the tumorigenicity of various tumours. In this study, we need to explore its role in hepatocellular carcinoma that remains largely elusive.

Materials and Methods

The expression of WISP3/CCN6 was analysed by qRT‐PCR and Western blotting. Effects of WISP3 on proliferation and metastasis of HCC cells were examined, respectively, by MTT assay and Boyden Chamber. Roles of WISP3 on HCC tumour growth and metastatic ability in vivo were detected in nude mice. Related mechanism study was confirmed by immunofluorescence and Western blotting.

Results

The expression of WISP3 was significantly downregulated in HCC clinical samples and cell lines, and reversely correlated with the tumour size. Forced expression of WISP3 in HCC cells significantly suppressed cell growth and migration in vitro as well as tumour growth and metastatic seeding in vivo. In contrast, downregulation of WISP3 accelerated cell proliferation and migration, and promoted in vivo metastasis. Further study revealed that WISP3 inhibited the translocation of β‐catenin to the nucleus by activating glycogen synthase kinase‐3β (GSK3β). Moreover, constitutively active β‐catenin blocked the suppressive effects of WISP3 on HCC.

Conclusions

Our study showed that WISP3 suppressed the progression of HCC by negative regulation of β‐catenin/TCF/LEF signalling, providing WISP3 as a potential therapeutic candidate for HCC.

[Contrastive analysis of ultrasonographic features of synchronous and heterochronic liver metastasis in patients with stromal tumor]

Objective: To investigate the ultrasonographic features of synchronous and heterochronic liver metastasis in patients with stromal tumors, and to elucidate the value of ultrasonic examination in follow-up surgery. Methods: A total of 1 516 patients with pathologically confirmed gastrointestinal stromal tumors (GISTs) and extra-gastrointestinal stromal tumors (EGISTs) were enrolled. The ultrasonographic features of primary lesions and liver metastases in a total of 46 cases with 95 liver metastases were analyzed. Results: 24 out of 46 cases had primary lesion in the small intestine, 14 in the stomach, 4 in the abdominal cavity, 1 in the colon, 2 in the esophagus, and 1 in the mesentery. The expression of CD117, Dog-1 and CD34were detected by immunohistochemical staining. The positive rate of CD117 was 100%, the Dog-1 was 95.7% and the CD34 was 69.6%. There were statistically significant differences in the maximum diameter, boundary and blood flow of primary tumors in 28 patients with synchronous liver metastasis and 18 patients with heterochronic liver metastasis (P=0.001, 0.022 and 0.036, respectively). Of the 95 liver metastases, 86 (90.5%) were located in the right lobe of the liver, 79 (83.2%) had clear boundaries, 75 (78.9%) were hypoechoic or isoechoic, 55 (57.9%) showed colored patterns, and 68 (71.6%) had no halo.11 liver metastases were cystic masses, 59 were solid masses, and 25 were mixed masses. There was a statistically significant difference in blood flow between 65 synchronous hepatic metastases and 30 heterochronic liver metastases (P=0.017). Conclusions: There were differences of the primary tumor ultrasonographic features between the synchronous metastasis group and heterochronic metastasis group. The ultrasonographic features of primary tumors and liver metastases have important clinical significance for the diagnosis, follow-up and treatment of malignant mesenchymal tumors.

A Ropivacaine-Lidocaine Combination for Caudal Blockade in Haemorrhoidectomy

A single dose of caudal lidocaine does not provide a sufficiently long anaesthetic duration and is not generally used for complicated anorectal surgery. This study evaluated the safety and efficacy of a ropivacaine–lidocaine combination for caudal anaesthesia in patients undergoing haemorrhoidectomy. A total of 287 haemorrhoid patients with successful initial caudal anaesthesia were randomized to receive either a mixture of 0.375% ropivacaine and 1.0% lidocaine (ropi–lido group; n = 146) or 1.0% lidocaine alone (placebo-lido group; n = 141). Significantly fewer patients in the ropi–lido group required intra-operative supplemental anaesthesia than in the placebo-lido group. Patients treated with the ropivacaine–lidocaine combination had significantly lower scores for pain at each post-operative time point, and a longer mean time to the first requirement for post-operative analgesic than patients in the placebo-lido group. These results suggest that caudal anaesthesia with a combination of ropivacaine and lidocaine is a safe and effective method of inducing anaesthesia during haemorrhoidectomy.

The endoplasmic reticulum may be an Achilles' heel of cancer cells that have undergone an epithelial-to-mesenchymal transition

In a recent report published in Cancer Discovery we identified a novel vulnerability of cancer cells that have undergone an epithelial–mesenchymal transition (EMT) and established that the PERK branch of the unfolded protein response is constitutively activated upon EMT. In this commentary, we summarize and provide context for our findings.

Epithelial-to-mesenchymal transition activates PERK-eIF2α and sensitizes cells to endoplasmic reticulum stress

Epithelial-to-mesenchymal transition (EMT) promotes both tumor progression and drug resistance, yet few vulnerabilities of this state have been identified. Using selective small molecules as cellular probes, we show that induction of EMT greatly sensitizes cells to agents that perturb endoplasmic reticulum (ER) function. This sensitivity to ER perturbations is caused by the synthesis and secretion of large quantities of extracellular matrix (ECM) proteins by EMT cells. Consistent with their increased secretory output, EMT cells display a branched ER morphology and constitutively activate the PERK-eIF2α axis of the unfolded protein response (UPR). Protein kinase RNA-like ER kinase (PERK) activation is also required for EMT cells to invade and metastasize. In human tumor tissues, EMT gene expression correlates strongly with both ECM and PERK-eIF2α genes, but not with other branches of the UPR. Taken together, our findings identify a novel vulnerability of EMT cells, and demonstrate that the PERK branch of the UPR is required for their malignancy.

SIGNIFICANCE

EMT drives tumor metastasis and drug resistance, highlighting the need for therapies that target this malignant subpopulation. Our findings identify a previously unrecognized vulnerability of cancer cells that have undergone an EMT: sensitivity to ER stress. We also find that PERK-eIF2α signaling, which is required to maintain ER homeostasis, is also indispensable for EMT cells to invade and metastasize.

RACK1 promotes non-small-cell lung cancer tumorigenicity through activating sonic hedgehog signaling pathway

Non-small-cell lung cancer (NSCLC) is a deadly disease due to lack of effective diagnosis biomarker and therapeutic target. Much effort has been made in defining gene defects in NSCLC, but its full molecular pathogenesis remains unexplored. Here, we found RACK1 (receptor of activated kinase 1) was elevated in most NSCLC, and its expression level correlated with key pathological characteristics including tumor differentiation, stage, and metastasis. In addition, RACK1 activated sonic hedgehog signaling pathway by interacting with and activating Smoothened to mediate Gli1-dependent transcription in NSCLC cells. And silencing RACK1 dramatically inhibited in vivo tumor growth and metastasis by blocking the sonic hedgehog signaling pathway. These results suggest that RACK1 represents a new promising diagnosis biomarker and therapeutic target for NSCLC.

Abstract 4473: Sorafenib suppresses postsurgical recurrence and metastasis of hepatocellular carcinoma in an orthotopic mouse model

Surgical resection is the first-line treatment for hepatocellular carcinoma (HCC) patients with well-preserved liver function. Nevertheless, postoperative recurrences occur up to 70% at 5 years, gravely jeopardizing the therapeutic outcome. Clearly, new approaches are needed for preventing relapse of this deadly disease. Taking advantage of a luciferase-labeled orthotopic xenograft model of HCC, we examined the role of Sorafenib, the first approved systemic drug for advanced HCC patients, in prevention of HCC recurrence. We found that Sorafenib suppressed the development of postsurgical intrahepatic recurrences, as well as abdominal metastasis, consequently leading to a prolonged postoperative survival of mice in this model. Furthermore, hyperactivity of ERK signaling caused by elevated levels of growth factors associated with postoperative liver regeneration enhanced the sensitivity of HCC cells to Sorafenib, providing a plausible explanation to the observation that recurrent tumors are more responsive to growth inhibition by Sorafenib. Our results strongly suggest a potential application of Sorafenib in early stage HCC patients who have received hepatectomy with curative intention, by effectively reducing postoperative recurrences.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4473. doi:10.1158/1538-7445.AM2011-4473

Sorafenib suppresses postsurgical recurrence and metastasis of hepatocellular carcinoma in an orthotopic mouse model

Surgical resection is the first-line treatment for hepatocellular carcinoma (HCC) patients with well-preserved liver function. Nevertheless, the rate of postoperative recurrence at 5 years is as high as 70%, and this gravely jeopardizes the therapeutic outcome. Clearly, new approaches are needed for preventing the relapse of this deadly disease. Taking advantage of a luciferase-labeled orthotopic xenograft model of HCC, we examined the role of sorafenib, the first systemic drug approved for advanced HCC patients, in the prevention of HCC recurrence. We found that sorafenib suppressed the development of postsurgical intrahepatic recurrence and abdominal metastasis and consequently led to prolonged postoperative survival of mice in this model. Furthermore, hyperactivity of extracellular signal-regulated kinase signaling caused by elevated levels of growth factors associated with postoperative liver regeneration enhanced the sensitivity of HCC cells to sorafenib; this provides a plausible explanation for the observation that recurrent tumors are more responsive to growth inhibition by sorafenib.

CONCLUSION

Our results strongly suggest that by effectively reducing postoperative recurrence, sorafenib has a potential application in early-stage HCC patients who have undergone hepatectomy with curative intention.

Liver cancer: EphrinA2 promotes tumorigenicity through Rac1/Akt/NF-kappaB signaling pathway

Eph/Ephrin family, one of the largest receptor tyrosine kinase families, has been extensively studied in morphogenesis and neural development. Recently, growing attention has been paid to its role in the initiation and progression of various cancers. However, the role of Eph/Ephrins in hepatocellular carcinoma (HCC) has been rarely investigated. In this study, we found that the expression of EphrinA2 was significantly up-regulated in both established cell lines and clinical tissue samples of HCC, and the most significant increase was observed in the tumors invading the portal veins. Forced expression of EphrinA2 in HCC cells significantly promoted in vivo tumorigenicity, whereas knockdown of this gene inhibited this oncogenic effect. We further found that suppression of apoptosis, rather than accelerating proliferation, was responsible for EphrinA2-enhanced tumorigenicity. In addition, EphrinA2 endowed cancer cells with resistance to tumor necrosis factor alpha (TNF-alpha)-induced apoptosis, thus facilitating their survival. Furthermore, we disclosed a novel EphrinA2/ras-related c3 botulinum toxin substrate 1 (Rac1)/V-akt murine thymoma viral oncogene homolog (Akt)/nuclear factor-kappa B (NF-kappaB) pathway contributing to the inhibitory effect on apoptosis in HCC cells.

CONCLUSION

This study revealed that EphrinA2 played an important role in the development and progression of HCC by promoting the survival of cancer cells, indicating its role as a potential therapeutic target in HCC.

Serum- and glucocorticoid-dependent kinase, cell volume, and the regulation of epithelial transport

Ample pharmacological evidence points to a role of kinases in the regulation of cell volume. Given the limited selectivity of most inhibitors, however, the specific molecules involved have remained largely elusive. The search for cell volume regulated genes in liver HepG2 cells led to the discovery of the human serum- and glucocorticoid-dependent serine/threonine kinase hsgk1. Transcription and expression of hsgk1 is markedly and rapidly upregulated by osmotic and isotonic cell shrinkage. The effect of osmotic cell shrinkage on hsgk1 is mediated by p38 kinase. Further stimuli of hsgk1 transcription include glucocorticoids, aldosterone, TGF-beta1, serum, increase of intracellular Ca2+ and phorbolesters, whereas cAMP downregulates hsgk1 transcription. The hsgk1 protein is expressed in several epithelial tissues including human pancreas, intestine, kidney, and shark rectal gland. Co-expression of hsgk1 with the renal epithelial Na+-channel ENaC or the Na+/K+/2Cl(-)-cotransporter NKCC2 (BSC1) in Xenopus oocytes, accelerates insertion of the transport proteins into the cell membrane and thus, stimulates channel or transport activity. Thus, hsgk1 participates in the regulation of transport by steroids and secretagogues increasing intracellular Ca2+-activity. The stimulation of hsgk1 transcription by TGF-beta1 may further bear pathophysiological relevance.

The genomic RNA in Ty1 virus-like particles is dimeric

The yeast retrotransposon Ty1 resembles retroviruses in a number of important respects but also shows several fundamental differences from them. We now report that, as in retroviruses, the genomic RNA in Ty1 virus-like particles is dimeric. The Ty1 dimers also resemble retroviral dimers in that they are stabilized during the proteolytic maturation of the particle. The stabilization of the dimer suggests that one of the cleavage products of TyA1 possesses nucleic acid chaperone activity.

The human immunodeficiency virus type 1 Gag polyprotein has nucleic acid chaperone activity: possible role in dimerization of genomic RNA and placement of tRNA on the primer binding site

The formation of an infectious retrovirus particle requires several RNA-RNA interaction events. In particular, the genomic RNA molecules form a dimeric structure, and a cellular tRNA molecule is annealed to an 18-base complementary region (the primer binding site, or PBS) on the genomic RNA, where it will serve as primer for reverse transcription. tRNAs normally possess a highly stable secondary and tertiary structure; it seems unlikely that annealing of a tRNA molecule to the PBS, which involves unwinding of this structure, could occur efficiently at physiological temperatures without the assistance of a cofactor. Many prior studies have shown that the viral nucleocapsid (NC) protein can act as a nucleic acid chaperone (i.e., facilitate annealing events between nucleic acids), and the assays used to demonstrate this activity include its ability to catalyze dimerization of transcripts representing retroviral genomes and the annealing of tRNA to the PBS in vitro. However, mature NC is not required for these events in vivo, since protease-deficient viral mutants, in which NC is not cleaved from the parental Gag polyprotein, are known to contain dimeric RNAs with tRNA annealed to the PBS. In the present experiments, we have tested recombinant human immunodeficiency virus type 1 Gag polyprotein for nucleic acid chaperone activity. The protein was positive by all of our assays, including the ability to stimulate dimerization and to anneal tRNA to the PBS in vitro. In quantitative experiments, its activity was approximately equivalent on a molar basis to that of NC. Based on these results, we suggest that the Gag polyprotein (presumably by its NC domain) catalyzes the annealing of tRNA to the PBS during (or before) retrovirus assembly in vivo.

HIV-1 nucleocapsid protein induces "maturation" of dimeric retroviral RNA in vitro

After a retrovirus particle is released from the cell, the dimeric genomic RNA undergoes a change in conformation. We have previously proposed that this change, termed maturation of the dimer, is due to the action of nucleocapsid (NC) protein on the RNA within the virus particle. We now report that treatment of a 345-base synthetic fragment of Harvey sarcoma virus RNA with recombinant or synthetic HIV-1 NC protein converts a less stable form of dimeric RNA to a more stable form. This phenomenon thus appears to reproduce the maturation of dimeric retroviral RNA in a completely defined system in vitro. To our knowledge, maturation of dimeric RNA within a retrovirus particle is the first example of action of an "RNA chaperone" protein in vivo. Studies with mutant NC proteins suggest that the activity depends upon basic amino acid residues flanking the N-terminal zinc finger and upon residues within the N-terminal finger, including an aromatic amino acid, but do not require the zinc finger structures themselves.

Multiple regions of Harvey sarcoma virus RNA can dimerize in vitro

Retroviruses contain a dimeric RNA consisting of two identical molecules of plus-strand genomic RNA. The structure of the linkage between the two monomers is not known, but they are believed to be joined near their 5' ends. Darlix and coworkers have reported that transcripts of retroviral RNA sequences can dimerize spontaneously in vitro (see, for example, E. Bieth, C. Gabus, and J. L. Darlix, Nucleic Acids Res. 18:119-127, 1990). As one approach to identification of sequences which might participate in the linkage, we have mapped sequences derived from the 5' 378 bases of Harvey sarcoma virus (HaSV) RNA which can dimerize in vitro. We found that at least three distinct regions, consisting of nucleotides 37 to 229, 205 to 272, and 271 to 378, can form these dimers. Two of these regions contain nucleotides 205 to 226; computer analysis suggests that this region can form a stem-loop with an inverted repeat in the loop. We propose that this hypothetical structure is involved in dimer formation by these two transcripts. We also compared the thermal stabilities of each of these dimers with that of HaSV viral RNA. Dimers of nucleotides 37 to 229 and 205 to 272 both exhibited melting temperatures near that of viral RNA, while dimers of nucleotides 271 to 378 are quite unstable. We also found that dimers of nucleotides 37 to 378 formed at 37 degrees C are less thermostable than dimers of the same RNA formed at 55 degrees C. It seems possible that bases from all of these regions participate in the dimer linkage present in viral RNA.

[Comparison of morphological and microscopical diagnostic characters of Hawthorn fruits (Crataegus species)]

This paper deals with studies on morphological and microscopical diagnostic characters of Chinese Hawthorn fruits. Their similarities and differences in morphological and microscopical characters among eight species of Crataegus (C. pinnatifida Bge., C. pinnatifida var. major NE Br., C. cuneata sieb. & Zuce., C. scabrifolia (Franch.) Rehd., C. hupehensis Sarg., C. kansuensis Wils, C. maximowiczii Schneid. and C. sanguinea Pall.) fruits are compared and illustrated with diagrams.

[Suppressive effects of adenosine on nonspecific and humoral immunities in mice]

Adenosine (Ade) 1.3, 13, 130 mg.kg-1 ip inhibited the ability of peripheral leukocytes and peritoneal macrophages in phagocytosing the Staphylococcus albus with [3H]TdR incorporation in mice, declined the hemolytic ability of plaque-forming cells and the production of antibody in mice immunized by sheep erythrocytes. Ade 13, 130 mg.kg-1 ip decreased the mouse serum muramidase (lysozyme) concentration. Dipyridamole (Dip) 10 mg.kg-1 ip attenuated the effects of Ade 130 mg.kg-1 on humoral immunity reaction, but the nonspecific immunity was not attenuated. These results showed that the uptake of Ade may play an important role in the effects of Ade on humoral immunity reaction. Aminophylline (Ami) 100 mg.kg-1 ip attenuated the effects of Ade 130 mg.kg-1 on hemolytic ability of plaque-forming cells and the ability of peripheral leukocytes in phagocytosing Staphylococcus albus. These results suggested that the effects of Ade on murine humoral and nonspecific immunity reaction were mediated by Ade A2 receptor (A2DR).

[A clinical and basic study on the relationship between acute myocardial infarction and endothelin]

The level of plasma endothelin (ET) was studied in 40 cases with acute myocardial infarction (AMI) with radioimmunoassay. The results showed that plasma ET level reached its peak value (46.01 +/- 1.64 pg/ml) immediately after AMI attack and dropped down (39.37 +/- 0.47 pg/ml) on the first day; The value was still high (15.56 +/- 1.40 pg/ml) on the twenty-eight day: this was significant higher than that in control group (6.35 +/- 0.44 pg/ml, P < 0.001). It was found that height of plasma ET level was closely correlated with severity of myocardial damage and degree of cardiac insufficiency. In order to evaluate the pathogenic role of ET in AMI, the effect of ET-antiserum on myocardial infarction (MI) was investigated on infarct model produced by ligature of left anterior descending coronary artery in rats. The results showed that plasma ET levels elevated significantly in rats with MI (8.4 +/- 1.0, sham 3.1 +/- 0.2 pg/ml, P < 0.01) and ET-antiserum administration dramatically decreased plasma ET level 65% (P < 0.01), lowered plasma content of lipid peroxide 27% (P < 0.01) and reduced infarct size 48% (P < 0.01). It is suggested that ET is an important factor which contributes to the pathogenesis of MI. Limb ischemia and reperfusion study was carried out in rats also. Metallothionein (MT) was found to antagonize markedly ET-induced vasoconstriction and lower the release of ET stimulated by angiotensin II in a dose-dependent manner. It is suggested that under certain pathological conditions MT may exert its injury--resistant and cell protective action.

[Constituents in volatile oil of peilan and 3 plants of the same genus]

A study hes been made on the essential oil from the crude drug Peilan (Eupatorium fortunei) and the plants E. japonicum, E. chinense and E. cannabinum. 71 constituents have been identified by GC-MS. Quantitative analysis has been carried out by GC. The study provides scientific methods for the identification of the crude drug "Peilan" and the quality control of the fresh and dried "Peilan".

Surgical treatment of atherosclerotic infrarenal abdominal aortic aneurysms. A review of 30 years' experience

During the 30 years from 1960 to 1989, 100 sequential patients with atherosclerotic infrarenal abdominal aortic aneurysm (AAA) were admitted to Zhongshan Hospital. Twenty-eight were not treated surgically and 72 underwent resection of the AAA with prosthesis replacement. Nineteen non-surgical patient were followed up, and 8 died from ruptures with a five-year survival rate of 41.3 +/- 13%. In 72 surgically treated patients, the operative mortality was 2.8%. The five-year survival rate is 77.5 +/- 6.2%, which is higher in comparison with the non-surgical group (P < 0.01). The data show that the operation for AAA is safe and the postoperative long-term results are satisfactory.

Bipartite signal for read-through suppression in murine leukemia virus mRNA: an eight-nucleotide purine-rich sequence immediately downstream of the gag termination codon followed by an RNA pseudoknot

The pol gene of murine leukemia virus and other mammalian type C retroviruses is expressed by read-through suppression of an in-frame UAG codon which separates the gag and pol coding regions. In this study, we have analyzed the sequence requirements for read-through suppression by placing different portions of wild-type and mutant viral sequences from the gag-pol junction between reporter genes and testing transcripts of these constructs for suppression in reticulocyte lysates. We find that the read-through signal is contained within the first 57 nucleotides on the 3' side of the UAG codon. Our results indicate that the identities of six conserved bases in the eight-nucleotide, purine-rich sequence immediately downstream of the UAG codon are critical for suppression, as is the existence of a pseudoknot structure spanning the next 49 nucleotides. Thus, read-through suppression depends on a complex, bipartite signal in the mRNA.

Identification of amino acids inserted during suppression of UAA and UGA termination codons at the gag-pol junction of Moloney murine leukemia virus

Expression of the murine leukemia virus pol gene occurs by translational readthrough of an in-frame UAG codon between the gag and pol coding regions. In a previous study, we mutated the UAG codon to UAA or UGA and demonstrated that both of these termination codons could be suppressed in reticulocyte lysates and in infected cells with the same efficiency as UAG. We now report the identity of the amino acids inserted in vitro in response to UAA and UGA in fusion products containing the gag-pol junction region. The results show that UAA, like UAG, directs the incorporation of glutamine, whereas UGA directs the incorporation of three amino acids, arginine, cysteine, and tryptophan. To our knowledge, this is the first report indicating misreading of UAA as glutamine and UGA as arginine and cysteine in higher eukaryotes. Interestingly, although our protein synthesis system presumably contains other known UAG and UGA suppressors, these tRNAs did not suppress the termination codons in our experiments. Thus, it seems possible that the sequence surrounding the gag-pol junction not only promotes suppression but also helps determine which tRNAs function in suppression.

Chromatographic analysis of the aminoacyl-tRNAs which are required for translation of codons at and around the ribosomal frameshift sites of HIV, HTLV-1, and BLV

An examination of the frameshift signals or proposed signals within published sequences of retroviruses and other genetic elements from higher animals shows that each site utilizes a tRNA which normally contains Wybutoxine (Wye) base or Queuine (Q) base in the anticodon loop. We find experimentally that most of the Phe-tRNA present in HIV-1 infected cells lacks the highly modified Wye base in its anticodon loop and most of the Asn-tRNA in HTLV-1 and BLV infected cells lacks the highly modified Q base in its anticodon loop. Interestingly, Phe-tRNA translates a UUU codon within the ribosomal frameshift signal in HIV and Asn-tRNA translates a AAC codon within the proposed frameshift signals in HTLV-1 and BLV. Thus, the lack of a highly modified base in the anticodon loop of tRNAs in retroviral infected cells is correlated with the participation of these undermodified tRNAs in the corresponding frameshift event. This suggests that the "shifty" tRNAs proposed by Jacks et al. (Cell 55, 447-458, 1988) to carry out frameshifting may be hypomodified isoacceptors.

Suppression of UAA and UGA termination codons in mutant murine leukemia viruses

Genomes of mammalian type C retroviruses contain a UAG termination codon between the gag and pol coding regions. The pol region is expressed in the form of a gag-pol fusion protein following readthrough suppression of the UAG codon. We have used oligonucleotide-directed mutagenesis to change the UAG in Moloney murine leukemia virus to UAA or UGA. These alternate termination codons were also suppressed, both in infected cells and in reticulocyte lysates. Thus, the signal or context inducing suppression of UAG in wild-type Moloney murine leukemia virus is also effective with UAA and UGA. Further, mammalian cells and cell extracts contain tRNAs capable of translating UAA and UGA as amino acids. To our knowledge, this is the first example of natural suppression of UAA in higher eucaryotes.

Translational readthrough of the murine leukemia virus gag gene amber codon does not require virus-induced alteration of tRNA

An in vitro system to assay translational readthrough of the UAG termination codon at the murine leukemia virus (MuLV) gag-pol junction was developed by using rabbit reticulocyte lysates programmed by SP6-generated Moloney MuLV gag-pol mRNA. Under conditions in which the suppressor activity of the lysate was dependent on addition of tRNA, it could be shown that readthrough synthesis was stimulated to approximately the same extent by equivalent amounts of tRNA from MuLV-infected and uninfected NIH 3T3 cells. Analysis of glutamine tRNA, which mediates suppression in vivo, showed that the level of glutamine acceptor activity and the chromatographic profile of glutamine isoacceptors were unchanged following virus infection. On the basis of these results, we conclude that the suppressor tRNA occurs normally within the tRNA population of uninfected cells and need not be induced in response to virus infection.

Transcriptional regulation of carnitine palmitoyltransferase synthesis in riboflavin deficiency in rats

Riboflavin deficiency leads to depressed mitochondrial fatty acid oxidation rates but increased activity of carnitine palmitoyltransferase (CPT). Starvation leads to increased CPT activity in ad libitum-fed, riboflavin-supplemented rats. The present studies examined the mechanism of the increase in CPT activity in riboflavin deficiency and whether it was additive to that seen in starvation. Rats were divided into three groups initially: riboflavin-sufficient, ad libitum-fed; riboflavin-deficient, ad libitum-fed; and pair-fed. These groups were subdivided after 5 wk into fed and 24- and 48-h starved groups. When riboflavin-deficient rats were starved for 24 or 48 h, there was only a 30-40% increase in hepatic CPT activity, in contrast to the ad libitum-fed, riboflavin-supplemented rats, in which activity increased twofold. CPT activity of pair-fed rats was similar to that of controls in the fed state and did not increase significantly with starvation. CPT translation, mRNA levels and transcription rates correlated with CPT activity, as did immunoreactive CPT. Concurrently, hepatic ketone production and plasma beta-hydroxybutyrate concentration increased during starvation in the control and pair-fed but not in the riboflavin-deficient rats. The results indicate that increased CPT activity in riboflavin deficiency and starvation results at least in part from increased synthesis. Furthermore, the data support previous work suggesting that the block in fatty acid oxidation occurs in the beta-oxidation pathway at the level of acyl-CoA dehydrogenases.

A simple and rapid solid-phase RNA sequencing method

A simple and rapid solid-phase RNA sequencing method has been developed based on Peattie's direct chemical method. 3'-Terminally labeled RNA was immobilized on DEAE-cellulose sheets and followed by specific modification with dimethyl sulfate, diethylpyrocarbonate, hydroxylamine (at pH 10 for the uridine and pH 5.5 for the cytidine reaction), and cleavage reaction with aniline. RNA fragments were washed from the DEAE-cellulose sheets using salt solutions, precipitated with ethanol, and separated by 15% polyacrylamide gel electrophoresis. Due to the complete removal of the impurities normally present in the solution method, the higher resolution of the sequencing bands and lower background on the autoradiograph make this solid-phase technique more efficient. This solid-phase technique is much faster and more convenient than the original method.

Exceptionally high and diverse mutation rates in insects small rRNA

The nucleotide sequence of 5S rRNA from the posterior silk gland of the silk worm Philosamia cynthia ricini has been determined. The comparison with other insect 5S rRNAs revealed an exceptionally conserved secondary structure, in spite of an extremely high mutation rate: Thirteen nucleotides are different in Philosamia and Drosophila 5S rRNA, but all substitutions are either compensatory or occur in loops or introduce G:U base pairs. The rates of base substitution per site per year of several insect species (diptera and lepidoptera) 5S and 5.8S rRNAs are compared with those occurring in vertebrate rRNAs. In the latter cases the rates are remarkably constant, whereas their value is not only about twofold higher in insect rRNAs, but is found to be extremely large in the 5S rRNA of the silkworm Bombyx mori. These data demonstrate that phylogenetic conclusions derived from small rRNA sequence comparisons are only of limited value.

The nucleotide sequence of 5.8S rRNA from the posterior silk gland of the silkworm Philosamia cynthia ricini

The nucleotide sequence of 5.8S rRNA from the Chinese silkworm Philosamia cynthia ricini has been determined by gel sequencing and mobility shift methods. The complete primary structure is (sequence in text). This is one of the largest known 5.8S rRNAs. As compared to Bombyx 5.8S rRNA, it is two nucleotides longer; two nucleotides near the 5'end and two nucleotides near the 3'end are different, and psi 61 of the Bombyx RNA sequence is an unmodified U in Philosamia RNA. The secondary structure of Philosamia 5.8S rRNA may differ from the Bombyx RNA structure by three additional base pairs at the 5'/3' ends.