Low-density lipoprotein (LDL) distribution shown by 99mtechnetium-LDL imaging in patients with myeloproliferative diseases

The value of bone marrow, liver, and spleen imaging in diagnosis, prognostication, and follow-up monitoring of myeloproliferative neoplasms: a systematic review

Background

Diagnostic and treatment response criteria for the JAK2/CALR/MPL mutation-related myeloproliferative neoplasms (MPNs) are largely based on bone marrow (BM) biopsy results. However, these biopsies have several limitations, such as the risk of sampling error. Also, the prognostic impact of BM abnormalities is largely unclear. Although not currently used in clinical practice, imaging techniques might offer additional information. In this review, we investigated the value of BM, liver, and spleen imaging for diagnosis, prognostication, and response monitoring of the JAK2/CALR/MPL mutation-related MPNs (i.e. essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF)).

Methods

A systematic literature search was performed via PubMed, Embase and the Cochrane Library up to 2020 March 26th. Of 5505 identified records, 55 publications met the eligibility criteria (i.e. containing original data on the imaging appearance of BM, spleen, or liver in adult ET, PV, or MF patients, published in a peer-reviewed journal, written in English).

Results

Many explorative studies described imaging features, sometimes with comparisons to clinical characteristics. Studies reporting measures of diagnostic accuracy included 1) splenic transient elastography to predict BM fibrosis grade in MF, 2) dynamic contrast-enhanced MRI to discern MF patients from ET patients and healthy controls, and 3) 18-fluorodeoxyglucose PET to detect residual disease after stem cell transplantation in MF. The diagnostic accuracies of radiography and ^99mTc-colloid scintigraphy were derived from several other articles. Except for the study on 18-fluorodeoxyglucose PET, we established substantial concerns regarding risk of bias and applicability across these studies, using the QUADAS-2 tool. Three publications described a correlation between imaging results and prognosis, of which one quantified the effect.

Conclusions

Based on current data, MRI (T1-weighted/STIR, Dixon) seems especially promising for the evaluation of BM fat content - and indirectly cellularity/fibrosis - in MF, and possibly for estimating BM cellularity in ET/PV. 18-fluorodeoxyglucose and 18-fluorothymidine PET/CT might be useful for evaluating BM fibrosis, with good reported accuracy of the former for the diagnosis of residual disease. Further research on these and other techniques is warranted to determine their exact value. Future researchers should improve methodology and focus on evaluation of diagnostic accuracy and prognostic implications of results.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40644-021-00405-7.

Development of a prognostically relevant cachexia index in primary myelofibrosis using serum albumin and cholesterol levels

Serum albumin and cholesterol levels predict survival in primary myelofibrosis, independent of each other and contemporary risk models. The cachexia index, determined by serum albumin and cholesterol levels, might further refine current prognostic models in myelofibrosis.

Myeloid cells regulate plasma LDL-cholesterol levels

PURPOSE OF REVIEW

Leukocytosis, elevated blood leukocyte levels, is associated with enhanced cardiovascular risk in humans. Hematopoietic stem and progenitor cells (HSPCs) drive leukocyte production in a process called hematopoiesis, which mainly occurs in the bone marrow, and under certain conditions also in other organs such as the spleen. Cholesterol accumulation in HSPCs enhances hematopoiesis, increasing levels of blood monocytes that infiltrate into atherosclerotic plaques. Although HSPC proliferation and monocytosis enhance atherogenesis in several studies, concomitant decreases in LDL-cholesterol levels have also been reported, associated with anti-atherogenic effects. This review focuses on the link between HSPC proliferation, leukocytosis, plasma LDL-cholesterol levels, and atherogenesis.

RECENT FINDINGS

Recent studies have shown that an acute infection enhances cholesterol accumulation in HSPCs, driving HSPC proliferation, and leading to the expansion of myeloid cells (monocytes, neutrophils, and macrophages). Enhanced hematopoiesis is associated with low plasma LDL-cholesterol levels in animal models and humans, probably because of the increased number of myeloid cells that take up LDL-cholesterol. Despite low-plasma LDL-cholesterol levels, specific patient populations with enhanced hematopoiesis show increased cardiovascular risk.

SUMMARY

Enhanced hematopoiesis and monocytosis may accelerate atherogenesis. Studies on these processes may lead to the identification of new therapeutic targets for cardiovascular diseases.

Prostaglandin I2-mediated upregulation of 125I-LDL-receptor binding by isradipine in normo- and hypercholesterolemic rabbits in vivo

The in-vivo low-density lipoprotein (LDL)-uptake by the liver was monitored during the initial 60 minutes after injection of radiolabelled LDL. LDL-uptake by the liver as evidenced by the liver/blood pool ratio in normocholesterolemic male New Zealand white rabbits (44.2 +/- 3.1% of whole body activity) was almost double as compared to the ones fed a 1% cholesterol enriched diet (22.5 +/- 3.3%). The blood disappearance of 125I-LDL was significantly faster in normocholesterolemic animals. A 4-week treatment with the dihydropyridine calcium channel blocker isradipine resulted in a significantly enhanced LDL-binding by the liver, both in normo- and hypercholesterolemic animals to a comparable extent. A concomitant acetylsalicylic acid (ASA) treatment completely abolished the benefit induced by isradipine while ASA alone was ineffective. Similarly, 125I-LDL disappearance from blood was improved by isradipine, while ASA neutralizes this effect. Again, ASA alone did not change the kinetics. Plasma cholesterol and high-density lipoprotein (HDL) cholesterol remained unchanged. Isradipine significantly enhanced vascular prostaglandin(PG)I2-generation while concomitant ASA treatment or ASA application alone almost completely depressed PGI2-formation. It is concluded that the improved LDL-binding by the liver is due to an enhanced PGI2-formation evoked by isradipine.

Disease-related hypocholesterolemia in patients with hairy cell leukemia. Positive correlation with spleen size but not with tumor cell burden or low density lipoprotein receptor activity

BACKGROUND

Hypocholesterolemia is common in patients with various malignant diseases, and may be a risk factor for the development or a consequence of the tumor, by different possible mechanisms.

METHODS

Serum lipids were analyzed in 66 patients with symptomatic hairy cell leukemia (HCL) before and repeatedly after treatment with cladribine. Low density lipoprotein (LDL) receptor activity of hairy cells from 12 patients was analyzed.

RESULTS

The median pretreatment serum cholesterol was 4.78 mmol/l. Total cholesterol, LDL cholesterol, and triglycerides were inversely correlated with the spleen size, but not with other markers of tumor burden. High density lipoprotein (HDL) cholesterol correlated to serum beta 2-microglobulin. Anemia and hypocholesterolemia developed synchronously before diagnosis in one patient. After cladribine therapy, there was a highly significant increase in all serum lipids. Low density lipoprotein receptor activity of HCL cells was elevated in only one of 12 patients; this patient had high serum cholesterol. Hypocholesterolemia predicted posttreatment neutropenic fever.

CONCLUSION

Hypocholesterolemia is a common disease-related finding in HCL, which is not caused by an increased LDL receptor activity of leukemia cells, but related to spleen size, predicts posttreatment fever, and is completely reverted after successful treatment of leukemia.

Relationship of apolipoprotein E phenotypes to hypocholesterolemia

PURPOSE

Persons with total cholesterol (TC) levels less than 130 mg/dL (less than 3.26 mmol/L) make up less than 1% of a healthy population. Causes of hypocholesterolemia include a diet very low in cholesterol and saturated fat, disease, genetic factors (including low apolipoprotein B-100 [apo B-100] and the apo E allele), and drug therapy. The purpose of this study was to determine the causes of hypocholesterolemia in a healthy Kaiser Foundation Health Plan (KFHP) population.

PATIENTS AND METHODS

We conducted a dietary and health survey of 201 healthy hypocholesterolemic adults (range: 2.04 to 3.88 mmol/L [79 to 150 mg/dL]) and 200 matched control subjects with TC levels in the middle quintile of the population (range: 5.0 to 5.61 mmol/L [194 to 217 mg/dL]) who had routine health screening from 1983 through 1985. We did apo E phenotyping studies and lipid and apo A-1 and B-100 measurements in a subgroup of 45 hypocholesterolemic subjects (mean TC level: 3.26 mmol/L [126 mg/dL]) and in a comparison group of 49 unmatched volunteers (mean TC level: 5.04 +/- 0.75 mmol/L [195 +/- 29 mg/dL]).

RESULTS

We found no differences in dietary intake or clinically significant medical illness between hypocholesterolemic and control subjects. In the hypocholesterolemic subgroup, we found an increased frequency of the apo E2 allele (epsilon 2) and a decreased frequency of the apo E4 allele (epsilon 4); the frequencies of the epsilon 2, epsilon 3, and epsilon 4 alleles were 33.3%, 63.3%, and 3.3%, respectively. The corresponding apo E allele frequencies in the comparison subgroup were 8.2%, 73.5%, and 18.4%, similar to those previously reported for the general population and significantly different from those found in the hypocholesterolemic subgroup (p < 0.0001). One hypocholesterolemic subject (a 46th patient) had a mutation in the apo B gene that resulted in the synthesis of a truncated species of apo B (apo B-46).

CONCLUSION

Our study indicates that hypocholesterolemia in our KFHP urban population is usually not caused by diet or disease. Biochemical factors, including the increased frequency of the apo E-2 phenotype and the decreased frequency of the apo E-4 phenotype, are more important.

Treatment of cancer patients with a low-density-lipoprotein delivery vehicle containing a cytotoxic drug

A cytotoxic drug (vincristine, VC) was incorporated into low-density lipoprotein (LDL) and given to cancer patients for the first time by repeated intravenous injection. Individuals presenting with ovarian or endometrial cancer received four or five weekly doses of 1.4 mg/m2 LDL/VC. The uptake of LDL/VC by the adrenal cortex and the liver was minimised by concurrent administration of prednisolone and chenodeoxycholic acid. No febrile, allergic or other reaction attributable to the LDL occurred, and no side effect on haemopoietic, adrenal or liver functions was observed. The neurotoxic side effects commonly seen during VC therapy appeared to be reduced. These results suggest that directed cytotoxic therapy might be achieved in humans through the use of LDL as a carrier. Thus, dose-range and comparative studies using LDL/VC vs VCSO4 are warranted in malignancies in which treatment with the latter drug has been established.

Malnutrition in tubefed nursing home patients with pressure sores

This study compares the nutritional status and dietary intake of 14 tubefed nursing home patients with pressure sores (age: 70 +/- 5 years, mean +/- SEM) to 12 tubefed patient-controls without sores (age: 60 +/- 7 years). Patients tended to have higher calorie intake (32 +/- 3 kcal/kg) than patient-controls (26 +/- 2 kcal/kg, p = 0.11). Protein intake was significantly higher in patients (1.4 +/- 0.2 g/kg) than patient-controls (0.9 +/- 0.1 g of protein per kg, p less than 0.05). Despite increased calorie and protein intake, biochemical measures of nutritional status were worse in the patients. Serum albumin was lower in patients (33 +/- 1 g/L) than in patient-controls (37 +/- 1 g/L, p less than 0.05) as was level of hemoglobin (patients: 117 +/- 5; patient-controls: 132 +/- 5 g/L, p less than 0.05). Patients with stage IV (severe) sores had lower serum cholesterol levels (3.46 +/- 0.31 mmol/L, n = 5) than patients with stage II/III (milder) sores (4.58 +/- 0.23 mmol/L, n = 9, p less than 0.05). Plasma zinc was low in both patients (11.2 +/- 0.6 mumol/L) and patient-controls (11.5 +/- 0.7 mumol/L, p = NS). Pressure sore surface area was positively correlated with calorie intake per kilogram of body weight (r = +0.59, p less than 0.04) and negatively correlated with body mass index (r = -0.70, p less than 0.03), hemoglobin (r = -0.55, p less than 0.07) and serum cholesterol (r = -0.57, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake of low density lipoproteins by human leukemic cells in vivo: relation to plasma lipoprotein levels and possible relevance for selective chemotherapy

The success of cancer chemotherapy is dependent on the possibility to utilize biological differences between malignant and normal cells to selectively destroy the tumor cells. One such difference may be that of receptor-mediated cellular uptake of low density lipoproteins (LDLs). Previous studies have shown that leukemic cells from patients with acute myelogenous leukemia have elevated receptor-mediated uptake and degradation rates of plasma LDL in vitro compared to normal white blood and bone marrow cells, and that plasma cholesterol levels at diagnosis are inversely correlated with the LDL receptor activity of the malignant cells. An important question is whether the uptake of LDL by the leukemic cells is also increased in vivo. To evaluate the in vivo uptake of LDL, 11 adult patients with newly diagnosed acute myelogenous leukemia received an i.v. injection of [14C]-sucrose-labeled LDL. On degradation of [14C]sucrose-LDL, the radiolabeled sucrose moiety is known to remain trapped in the lysosomal compartment of the cells. After injection, radioactivity accumulated progressively for at least 12 hr in the leukemic cells. The uptake of radioactivity in vivo correlated with the rate of receptor-mediated degradation of 125I-labeled LDL by the leukemic cells assayed in vitro (r = +0.88, P less than 0.001). An inverse correlation between plasma LDL cholesterol concentrations and the in vivo cellular uptake of [14C]sucrose-LDL in whole blood (r = -0.76, P less than 0.01) indicates that the hypocholesterolemia is due to elevated LDL uptake by the leukemic cells. Postmortem biopsies from virtually all tissues were obtained from one patient, and the distribution of radioactivity revealed that the liver and bone marrow had accumulated most radioactivity; the adrenals had the highest uptake of label per gram of tissue weight. The results indicate that LDL may be used as a carrier targeting lipophilic cytotoxic drugs to leukemic cells.

Noninvasive imaging of 99mtechnetium-labeled low density lipoprotein uptake by tendon xanthomas in hypercholesterolemic patients

Technetium-labeled low density lipoproteins (Tc-LDL) appear to be useful for describing LDL biodistribution in normal and dyslipidemic subjects. We injected 99mTc-LDL into subjects with large tendon xanthomas secondary to homozygous familial hypercholesterolemia or sitosterolemia. Rapid (4 hours) accumulation of Tc-99m activity in xanthomas was observed, and this accumulation increased over a 24-hour period. No comparable accumulations of Tc-99m activity were noted in normal subjects or in a subject with heterozygous familial hypercholesterolemia who had very small tendon xanthomas. These findings support previous biopsy data indicating active uptake of LDL by macrophages within xanthoma and suggest that 99mTc-LDL imaging of xanthomas may be useful in studies of the effects of diet and drugs on the accumulation of lipoproteins by atherosclerotic plaques.

99mTc-low density lipoprotein: intracellularly trapped radiotracer for noninvasive imaging of low density lipoprotein metabolism in vivo

Low density lipoprotein (LDL) is the major transport protein for endogenous cholesterol in human plasma. LDL can be radiolabeled with 99mTc using sodium dithionite as a reducing agent. Biodistribution studies of 99mTc-LDL in normal rabbits confirm that 99mTc-LDL acts as an intracellularly "trapped ligand" similar to radioiodinated tyramine cellobiose-LDL (the previously validated trapped radioligand). In addition, studies performed in hypercholesterolemic rabbit models demonstrated the feasibility of imaging hepatic LDL-receptor concentration noninvasively. 99mTc-LDL imaging studies in a number of hypercholesterolemic and hypocholesterolemic patients have proven useful in understanding the abnormal uptake and metabolism of LDL. In patients with hypercholesterolemia (HC), 99mTc-LDL appears to be taken up well by the actively evolving atherosclerotic lesions and xanthomata that contained foam cells and macrophages. In patients with myeloproliferative disease and chronic hypocholesterolemia, 99mTc-LDL images showed intense accumulation of radioactivity in the spleen and bone marrow; this demonstrated extensive proliferation of the macrophage population suggesting that hypocholesterolemia in these patients may be due to increased uptake of LDL uptake by the macrophages. 99mTc-LDL is a powerful tool for the noninvasive exploration of a variety of disorders of lipoprotein metabolism in patients.