Hemoglobin A synthesis in the developing fetus

Polyploid giant cancer cells and cancer progression

Polyploid giant cancer cells (PGCCs) are an important feature of cellular atypia, the detailed mechanisms of their formation and function remain unclear. PGCCs were previously thought to be derived from repeated mitosis/cytokinesis failure, with no intrinsic ability to proliferate and divide. However, recently, PGCCs have been confirmed to have cancer stem cell (CSC)-like characteristics, and generate progeny cells through asymmetric division, which express epithelial-mesenchymal transition-related markers to promote invasion and migration. The formation of PGCCs can be attributed to multiple stimulating factors, including hypoxia, chemotherapeutic reagents, and radiation, can induce the formation of PGCCs, by regulating the cell cycle and cell fusion-related protein expression. The properties of CSCs suggest that PGCCs can be induced to differentiate into non-tumor cells, and produce erythrocytes composed of embryonic hemoglobin, which have a high affinity for oxygen, and thereby allow PGCCs survival from the severe hypoxia. The number of PGCCs is associated with metastasis, chemoradiotherapy resistance, and recurrence of malignant tumors. Targeting relevant proteins or signaling pathways related with the formation and transdifferentiation of adipose tissue and cartilage in PGCCs may provide new strategies for solid tumor therapy.

Genetic Aspects and Immune Responses in Covid-19: Important Organ Involvement

In the last two decades, the world has experienced outbreaks of three major coronaviruses with high morbidity and mortality rates. The most recent of these started in the form of an unusual viral pneumonia in Wuhan, China, and now the world is facing a serious pandemic. This new disease has been called COVID-19 and is caused by the SARS-CoV-2 virus. Understanding the specific genetic and phenotypic structure of SARS-CoV-2 in COVID-19 pathogenesis is vital in finding appropriate drugs and vaccines. With this in mind, this review sheds light on the virology, genetics, immune-responses, and mechanism of action of this virus.

Generation of erythroid cells from polyploid giant cancer cells: re-thinking about tumor blood supply

INTRODUCTION

During development and tumor progression, cells need a sufficient blood supply to maintain development and rapid growth. It is reported that there are three patterns of blood supply for tumor growth: endothelium-dependent vessels, mosaic vessels, and vasculogenic mimicry (VM). VM was first reported in highly aggressive uveal melanomas, with tumor cells mimicking the presence and function of endothelial cells forming the walls of VM vessels. The walls of mosaic vessels are randomly lined with both endothelial cells and tumor cells. We previously proposed a three-stage process, beginning with VM, progressing to mosaic vessels, and eventually leading to endothelium-dependent vessels. However, many phenomena unique to VM channel formation remain to be elucidated, such as the origin of erythrocytes before VM vessels connect with endothelium-dependent vessels.

RESULTS

In adults, erythroid cells are generally believed to be generated from hematopoietic stem cells in the bone marrow. In contrast, embryonic tissue obtains oxygen through formation of blood islands, which are largely composed of embryonic hemoglobin with a higher affinity with oxygen, in the absence of mature erythrocytes. Recent data from our laboratory suggest that embryonic blood-forming mechanisms also exist in cancer tissue, particularly when these tissues are under environmental stress such as hypoxia. We review the evidence from induced pluripotent stem cells in vitro and in vivo to support this previously underappreciated cell functionality in normal and cancer cells, including the ability to generate erythroid cells. We will also summarize the current understanding of tumor angiogenesis, VM, and our recent work on polyploid giant cancer cells, with emphasis on their ability to generate erythroid cells and their association with tumor growth under hypoxia.

CONCLUSION

An alternative embryonic pathway to obtain oxygen in cancer cells exists, particularly when they are under hypoxic conditions.

Generation of erythroid cells from fibroblasts and cancer cells in vitro and in vivo

Bone marrow is generally considered the main source of erythroid cells. Here we report that a single hypoxia-mimic chemical, CoCl2, can increase the size of fibroblasts and cancer cells and lead to formation of polyploidy giant cells (PGCs) or polyploidy giant cancer cells (PGCCs), activation of stem cell marker expression, increased growth of normal and cancer spheroid, and lead to differentiation of the fibroblasts and epithelial cells toward erythroid lineage expressing hemoglobins both in vitro and in vivo. Immunohistochemical examination demonstrated that these cells are predominantly made of embryonic hemoglobins, with various levels of fetal and adult hemoglobins. Ectopic expression of c-Myc induced the generation of nucleated erythoid cells expressing variable levels of embryonic and fetal hemoglobins. Generation of these erythroid cells can be also observed via histological examination of other cancer cell lines and human tumor samples. These data suggest that normal and solid cancer cells can directly generate erythroid cells to obtain oxygen in response to hypoxia and may explain the ineffectiveness of conventional anti-angiogenic therapies for cancer, which are directed at endothelium-dependent vessels, and offer new targets for intervention.

Thalassemia: The Continued Challenge

This overview describes the history of transfusion therapy and consequent iron overload in thalassemia. It emphasizes the importance of measurement of hepatic iron and reviews the history of chelation therapy. It briefly describes the discoveries of the genetic basis of thalassemia and the application of that knowledge in prenatal diagnosis. The review goes on to emphasize pharmaceutical efforts to induce fetal hemoglobin synthesis in thalassemic red cells and ends with a discussion of oral iron chelators, stem cell transplant, and the status of gene therapy.

Expression, purification, and characterization of human hemoglobins Gower-1 (zeta(2)epsilon(2)), Gower-2 (alpha(2)epsilon(2)), and Portland-2 (zeta(2)beta(2)) assembled in complex transgenic-knockout mice

Embryonic zeta- and epsilon-globin subunits assemble with each other and with adult alpha- and beta-globin subunits into hemoglobin heterotetramers in both primitive and definitive erythrocytes. The properties of these hemoglobins-Hbs Gower-1 (zeta(2)epsilon(2)), Gower-2 (alpha(2)epsilon(2)), and Portland-2 (zeta(2)beta(2))-have been incompletely described as they are difficult to obtain in quantity from either primary human tissue or conventional expression systems. The generation of complex transgenic-knockout mice that express these hemoglobins at levels between 24% and 70% is described, as are efficient methods for their purification from mouse hemolysates. Key physiological characteristics-including P(50), Hill coefficient, Bohr effect, and affinity for 2,3-BPG-were established for each of the 3 human hemoglobins. The stability of each hemoglobin in the face of mechanical, thermal, and chemical stresses was also determined. Analyses indicate that the zeta-for-alpha exchange distinguishing Hb Portland-2 and Hb A alters hemoglobin O(2)-transport capacity by increasing its P(50) and decreasing its Bohr effect. By comparison, the epsilon-for-beta exchange distinguishing Hb Gower-2 and Hb A has little impact on these same functional parameters. Hb Gower-1, assembled entirely from embryonic subunits, displays an elevated P(50) level, a reduced Bohr effect, and increased 2,3-BPG binding compared to Hb A. The data support the hypothesis that Hb Gower-2, assembled from reactivated epsilon globin in individuals with defined hemoglobinopathies and thalassemias, would serve as a physiologically acceptable substitute for deficient or dysfunctional Hb A. In addition, the unexpected properties of Hb Gower-1 call into question a common hypothesis for its primary role in embryonic development.

The switch from fetal to adult erythropoiesis

The story of the developmental changes in erythropoiesis is the history of oxygenation in the developing organism. The individual components of the switch from embryonic to adult erythropoiesis are developmentally regulated, and their interaction with one another is complex. Basic defects, such as absence of Epo production, lead to early embryonic or fetal death. Other defects, such as abnormalities in the switch from the fetal to adult erythropoiesis, are less catastrophic but result in hematologic abnormalities. Understanding the many aspects of the switch from embryonic to fetal to adult erythropoiesis can lead to an improved awareness of many of the problems typical of preterm infants, inborn errors resulting in hematologic diseases, and aspects important for transplantation medicine.

The developmental regulation of the human zeta-globin gene in transgenic mice employing beta-galactosidase as a reporter gene

We have investigated the developmental and tissue specific expression of the human embryonic zeta-globin gene in transgenic mice. A construct containing 550 bp of zeta-globin 5' flanking region, fused to a beta-galactosidase (lacZ) reporter gene and linked to the locus control region (LCR)-like alpha positive regulatory element (alpha PRE) was employed for the production of transgenic mice. Firstly, we compared the number of live born transgenic mice containing this construct to the number of live born transgenic mice containing the entire zeta-globin gene linked to the alpha PRE or the beta LCR. Data showed that 12% of mice generated from eggs injected with zeta-promoter/lacZ/alpha PRE DNA were transgenic compared to only 2% of mice generated from eggs injected with the entire zeta-globin gene linked to the alpha PRE or the beta LCR. The reduced number of live born transgenic mice containing the latter constructs suggests that death of transgenic embryos, possibly due to thalassaemia, may be occurring. X-gal staining of whole embryos containing the lacZ gene revealed that zeta-globin promoter activity was most pronounced at 8.5-9.5 days of development and was restricted to erythroid cells. By 15 days of development, no zeta-globin promoter activity was detected. These results suggest that the alpha PRE can direct high level expression from the zeta-globin promoter and that sequences required for the correct tissue and developmental specific expression of the human zeta-globin gene are present within 550 bp's of 5' flanking region. Sequences within the body of the zeta-globin gene or 3' of the cap site do not appear to be necessary for correct zeta-globin developmental regulation.

Human alpha-globin genes demonstrate autonomous developmental regulation in transgenic mice

Recent studies have demonstrated that transcriptional activation of the human adult beta-globin transgene in mice by coinsertion of the beta-globin cluster locus control region (beta-LCR) results in loss of its adult restricted pattern of expression. Normal developmental control is reestablished by coinsertion of the fetal gamma-globin transgene in cis to the adult beta-globin gene. To test the generality of this interdependence of two globin genes for their proper developmental control, we generated transgenic mice in which the human adult alpha-globin genes are transcriptionally activated by the beta-LCR either alone or in cis to their corresponding embryonic zeta-globin gene. In both cases, the human globin transgenes were expressed at the appropriate developmental period. In contrast to the beta-globin gene, developmental control of the human adult alpha-globin transgenes appears to be autonomous and maintained even when activated by an adjacent locus control region.

Human alpha-globin genes demonstrate autonomous developmental regulation in transgenic mice

Recent studies have demonstrated that transcriptional activation of the human adult beta-globin transgene in mice by coinsertion of the beta-globin cluster locus control region (beta-LCR) results in loss of its adult restricted pattern of expression. Normal developmental control is reestablished by coinsertion of the fetal gamma-globin transgene in cis to the adult beta-globin gene. To test the generality of this interdependence of two globin genes for their proper developmental control, we generated transgenic mice in which the human adult alpha-globin genes are transcriptionally activated by the beta-LCR either alone or in cis to their corresponding embryonic zeta-globin gene. In both cases, the human globin transgenes were expressed at the appropriate developmental period. In contrast to the beta-globin gene, developmental control of the human adult alpha-globin transgenes appears to be autonomous and maintained even when activated by an adjacent locus control region.

Globin gene expression in erythroid human fetal liver cells

We measured steady-state levels of the human globin mRNAs in liver samples from several mid-gestational fetuses. RNA from the epsilon, gamma, beta, zeta, theta, and alpha globin genes were present in fetal liver samples isolated from 10-25-wk embryos. The abundance of all human globin mRNAs declined in older fetuses, presumably because of a gradual reduction in the proportion of erythroid precursors in the liver as development proceeds. The gamma:beta globin mRNA ratio in 10-18-wk fetal erythroblasts was 6-7:1, and in adult erythroid bone marrow the ratio was 0.02:1. In fetal liver samples, the relative abundance of epsilon transcripts was less than 1% that of gamma, and zeta transcripts less than 5% that of alpha. Embryonic transcripts declined in abundance during late fetal development and were not detected in newborn liver or adult erythroid bone marrow. theta globin mRNA also represented a minor species (less than 1% that of alpha) in fetal liver samples, but in contrast to the embryonic mRNAs, was most abundant in adult marrow samples obtained from patients with erythroid hyperplasia. These results support the hypothesis that globin protein levels are regulated by the relative amounts of each globin mRNA at various stages of erythropoietic development.

Haemoglobin switching in human embryos: asynchrony of zeta----alpha and epsilon----gamma-globin switches in primitive and definite erythropoietic lineage

Haemoglobin switching in humans provides a unique model for investigating the mechanisms underlying expression of a developmentally regulated gene family. Numerous studies have focused on the switch from fetal to adult (that is, gamma----beta) globin, but little is known about the embryonic----fetal (that is, zeta----alpha and epsilon----gamma) switches, as well as the transition from 'primitive' yolk sac to 'definitive' liver erythropoiesis. Here we have studied the embryonic----fetal haemoglobin switches in yolk sac, liver and circulating blood erythroblasts from 25 embryos and 6 fetuses. Globin synthesis was also evaluated in purified 'primitive' and 'definitive' erythroblasts. Primitive erythroblasts synthesize essentially zeta and epsilon chains at 5 weeks and alpha- and epsilon-globin with a minor aliquot of zeta and gamma chains at 6-7 weeks, whereas definitive erythroblasts produce alpha and epsilon + gamma + beta-globin at 6 weeks but only alpha and gamma + beta chains from 8 weeks onward. In both lineages the zeta----alpha and the epsilon----gamma switches are asynchronous, the former preceding the latter. Furthermore, zeta- and beta-globin synthesis is restricted to primitive and definitive erythroblasts respectively. These findings are discussed in terms of a monoclonal model for haemoglobin switching in early human ontogeny.

Developmental changes in human erythrocyte carbonic anhydrase levels: coordinate expression with adult hemoglobin

In order to bolster the argument that parallel developmental changes in erythrocyte adult hemoglobin (HbA) and carbonic anhydrase (CA) content provide a potentially suitable model for the dissection of coordinate gene expression, the magnitude of fetal vs adult differences in CA I and CA II levels was examined in human red cell subpopulations obtained after varying periods of exposure to CA-dependent, NH4Cl-HCO-3-mediated, acetazolamide-modulated hemolysis. When content of CA I and CA II was immunologically assessed in cohorts surviving successively longer periods of hemolysis, cord blood red cells were divisible into two populations. Fifteen to thirty percent are rapidly disrupted and have CA I and CA II concentrations similar to those in adult blood erythrocytes. The remaining 70 to 85% have CA I concentrations which are 100-fold less and CA II concentrations which are 5- to 20-fold less than those found in adults. Thus, contrary to past reports, the magnitude of the developmental change in CA I concentration closely resembles the magnitude of change in HbA levels.

The synthesis of adult hemoglobins during hepatic erythropoiesis in the calf fetus

We investigated hemoglobin synthesis in suspension cultures of liver erythroid cells obtained from calf fetuses of 103 to 198 days. A significant amount of radioactivity was associated with adult hemoglobins which were separated from the fetal hemoglobins by isoelectric focusing, even after purification of the cell hemolysates by chromatography on Sephadex G-100. A radioactive beta-globin fraction was isolated by chromatography on carboxymethyl-cellulose from hemolysates, which were first fractionated on Sephadex G-100. Fingerprint analysis of peptides obtained by trypsinolysis of radioactive beta-globin chains revealed that its structure was closely related to that of beta-globin, isolated from cow bone marrow cells. The amount of beta-globin which was synthesized by calf liver cells varied from 0.3 to 3.5% of the non-alpha globin chains and remained at a low level for all the fetuses which were studied. Our results indicate that the bovine fetal liver is a valuable model to investigate the switch from fetal to adult hemoglobin synthesis.

Clinical features of thalassemia

The thalassemia syndromes are an important group of diseases in childhood, frequently encountered in many ethnic groups worldwide. Heterozygotes are frequently misdiagnosed as having iron deficiency anemia, and the more severely affected homozygotes present major problems in management. Advances in prenatal diagnosis offer hope for prevention, while progress in transfusion therapy, accuracy of prediction of value of splenectomy, and chelation therapy offer improved quality and, perhaps, duration of life.

Thalassemia and pregnancy: results of an antenatal screening program

A thalassemia screening program was implemented at our institution using the finding of a mean corpuscular volume less than 80 fl as the index of abnormality. Further evaluation using hemoglobin (Hb) electrophoresis and serum iron studies was carried out according to the scheme detailed below. A diagnosis of thalassemia was made in 33 women (42 pregnancies). Eight patients had alpha-thalassemia trait, 23 beta-thalassemia trait, and two Hb H disease. Thalassemia trait did not have any adverse effect on pregnancy outcome. In two couples the fetuses were at risk for homozygous disease and in one couple the fetus was at risk for sickle cell beta-thalassemia. The screening program described is an effective and inexpensive means of detecting thalassemia in an antenatal population and is applicable to most every clinic or office setting.

Prenatal diagnosis of hemoglobinopathies

Techniques are currently available at a few specialized centers for the antenatal detection of hemoglobinopathies such as beta thalassemia and sickle cell anemia. The risks are not yet clearly defined, but it seems reasonable to suggest that about 90 per cent of families may obtain useful information about the genotype of their fetus. Obtaining fetal blood as well as analyzing the sample requires considerable experience and skill. These factors continue to limit the availability of this procedure.

Radioimmunoassay for abnormal hemoglobins

A sensitive and specific radioimmunoassay has been developed for the identification or quantification of the human hemoglobin variants S, C, D-Los Angeles, E, G Philadelphia, Russ, O Arab, Beograd, J Paris I, G San Jose, Q Iran, Korle Bu, and F Malta I. In the immunoassay, monospecific antibody preparations are used which recognize the single amino acid substitution in the variant polypeptide chail and do not cross-react with normal hemoglobins or hemoglobin variants containing a different amino acid exchange at the same position.

Unequal accumulation of alpha- and beta-globin mRNA in erythropoietic mouse spleen

Relative amounts and rates of synthesis of alpha- and beta-globin mRNAs were determined during splenic erythropoiesis in mice. At times after injection of mice with phenylhydrazine, alpha- and beta-globin mRNAs were separated by gel electrophoresis and quantitated by densitometric scanning of stained gels. At 66 hr after injection, the ratio of beta to alpha mRNA is about 1.2. By 138 hr, total globin mRNA is 5-fold greater in spleen cells, and the beta to alpha mRNA ratio approaches 2. This ratio remains around 1 in reticulocytes throughout this period. Analyses of globin products directed by these mRNAs from spleen cells and reticulocytes in the ascites cell-free system reflect the beta to alpha mRNA ratio observed by electrophoresis. Relative rates of synthesis of globin mRNAs were estimated after incubation of spleen cells with either [3H] uridine or [3H] adenosine. Although synthesis of both mRNAs is maximal at 114 hr and then declines sharply, beta mRNA is synthesized at a greater rate than alpha mRNA at every developmental stage. In contrast to the excess accumulation of beta mRNA in spleen cells, synthesis of alpha- and beta-globin chains remains balanced throughout erythroid development. These data suggest that during erythropoiesis in this system, equal synthesis of alpha and beta globin involves regulation at both transcriptional and post-transcriptional levels.

Expression of the beta-thalassemia gene in the first trimester fetus

To determine whether beta-thalassemia can be detected in the fetus, blood was obtained from abortuses of normal mothers and of mothers with beta-thalassemia trait. The red cells were incubated with radioactive leucine and the globin chains were analyzed by radiochromatography. Two independent methods were utilized to correct the results for contamination by maternal radioactive beta-chain, and the corrected beta/gamma ratios were compared to a previously established range of normal fetal beta/gamma synthetic ratios obtained by similar measurements in pure fetal cells. In the erythroid cells of three fetuses from mothers with beta-thalassemia trait, the beta/gamma synthetic ratio was normal in two. The third had a beta/gamma ratio of 0.04 at 10 1/2 weeks, a 50% reduction, consistent with fetal beta-thalassemia trait. Two other fetuses, derived from parents both of whom had beta-thalassemia trait, were also studied. One had a beta/gamma ratio of 0.029 at 8 weeks, a 65% reduction, also consistent with beta-thalassemia trait. The cells of the other had a ratio of essentially zero at 11 weeks, highly suggestive of homozygous beta-thalassemia. Although further experience will be needed to distinguish the homozygous and heterozygous states reliably, it now appears that the beta-thalassemia gene is expressed in the first trimester. Therefore these data suggest that the antenatal diagnosis of beta-thalassemia is becoming an attainable goal.

Successful application of prenatal diagnosis in a pregnancy at risk for homozygous beta-thalassemia

A Sicilian couple whose first child had homozygous beta-+-thalassemia requiring monthly transfusion requested prenatal diagnosis during the second pregnancy. Fully informed consent was obtained. The placenta was localized by ultra-sound at the 20th week of gestation, and was aspirated with a 20-gauge needle. Samples containing fetal red cells were obtained, and studies of globinchain synthesis showed a normal beta/gamma synthesis ratio for this gestational age. The conclusion that the child was not affected by beta-thalassemia was confirmed when an infant not affected with homozygous of heterozygous beta-thalassemia was born at term. Although more experience with this approach is necessary, this study demonstrates that prenatal diagnosis or exclusion of beta-thalassemia and sickle-cell anemia is feasible.

The postnatal decline of hemoglobin F synthesis in normal full-term infants

Studies were carried out during the 1st yr of life in normal infants born at term to determine the proportions of fetal hemoglobin (Hb F) and adult hemoglobin (Hb A) being synthesized, in order to describe the complete switchover from Hb F to Hb A synthesis during postnatal life. 53 blood samples from 37 infants were incubated in an amino acid mixture containing [14C]leucine and chromatographed on DEAE-Sephadex for separation of Hb F and Hb A fractions. The completeness of the CEAE-Sephadex separation of Hb A and Hb F at an age when the major portion of synthesis was of the adult type of hemoglobin was confirmed by globin chain chromatography with the use of carboxylmethyl cellulose. There was a rapid decline in Hb F synthesis postnatally until 16-20 wk of age when levels of 3.2% plus or minus SD 2.1% were reached. By combining this data with that previously published, the complete switchover from Hb F to Hb A synthesis can be described in humans in relation to postconceptional age. It follows a sigmoid curve; the steep portion, which lies between the 30th and 52nd postconceptional week, is preceded and follwoed by plateaus averaging 95% and 7% Hb F synthesis, respectively.

[Neonatal polycythaemia and haemoglobin types in infants with G-trisomy (author's transl)]

The concentrations of haemoglobin A1, A2, and F were determined quantitatively by column chromatography in 11 newborns with G-trisomy (Down's Syndrome)) and correlated to haematocrit values. In 3 infants the haemoglobin pattern was followed throughout the first six months of life. In connection to the well know polycythaemia, newborns with G-trisomy were found to have significantly higher haemoglobin A1 attaining 35.5 plus or minus 6.6% and A2 equal to 0.79 plus or minus 0.32% as compared to normal infants (HbA1 equal 17.74 plus or minus 4.56%, HbA2 equal to 0.25 plus or minus 0.2%). In G-trisomy the switch-over from synthesis of haemoglobin F to haemoglobin A appears to be initiated earlier than in normal individuals, and it seems even to proceed more rapidly during the first weeks after birth. The amount of adult haemoglobin being synthesized in G-trisomy during the perinatal period may possibly be a response to the increased erythropoiesis, while the influence of chromosomal abnormality seems not to be a specific phenomenon.

Further evidence of a quantitative deficiency of chain-specific globin mRNA in the thalassemia syndromes

Formamide gel electrophoresis separates the mRNA fraction from reticulocyte polyribosomes of adult humans into two major RNA species with migratory rates identical to those of the alpha- and beta-globin mRNAs of the rabbit. That these two RNAs of human origin are the globin mRNAs is further supported by the deficiency of the presumed beta mRNA in reticulocyte polyribosomes of fetuses and premature infants, whose cells make gamma chains in preference to beta chains. The globin mRNAs of reticulocyte polyribosomes from patients with hematological disorders were estimated by scanning the stained formamide gels. In contrast to individuals with either hemolytic anemia without hemoglobinopathy or sickle cell anemia who had beta mRNA to alpha mRNA ratios of approximately one, a patient with Hb S-beta-thalassemia had a ratio of beta mRNA to alpha mRNA of 0.75 while two subjects with homozygous beta-thalassemia had severe deficiencies of beta mRNA. Conversely, a patient with alpha-thalassemia (Hb H disease) had a ratio of beta mRNA to alpha mRNA on reticulocyte polyribosomes of 6. These data provide further evidence of a quantitative deficiency of chain-specific globin mRNA in patients with the thalassemia syndromes.