Detection of hTERT protein by flow cytometry

Artificial Intelligence-Derived Electrocardiogram Assessment of Cardiac Age and Molecular Markers of Senescence in Heart Failure

OBJECTIVE

To ascertain whether heart failure (HF) itself is a senescent phenomenon independent of age, and how this is reflected at a molecular level in the circulating progenitor cell niche, and at a substrate level using a novel electrocardiogram (ECG)-based artificial intelligence platform.

PATIENTS AND METHODS

Between October 14, 2016, and October 29, 2020, CD34⁺ progenitor cells were analyzed by flow cytometry and isolated by magnetic-activated cell sorting from patients of similar age with New York Heart Association functional classes IV (n = 17) and I-II (n = 10) heart failure with reduced ejection fraction and healthy controls (n = 10). CD34⁺ cellular senescence was quantitated by human telomerase reverse transcriptase expression and telomerase expression by quantitative polymerase chain reaction, and senescence-associated secretory phenotype (SASP) protein expression assayed in plasma. An ECG-based artificial intelligence (AI) algorithm was used to determine cardiac age and difference from chronological age (AI ECG age gap).

RESULTS

CD34⁺ counts and telomerase expression were significantly reduced and AI ECG age gap and SASP expression increased in all HF groups compared with healthy controls. Expression of SASP protein was closely associated with telomerase activity and severity of HF phenotype and inflammation. Telomerase activity was more closely associated with CD34⁺ cell counts and AI ECG age gap.

CONCLUSION

We conclude from this pilot study that HF may promote a senescent phenotype independent of chronological age. We show for the first time that the AI ECG in HF shows a phenotype of cardiac aging beyond chronological age, and appears to be associated with cellular and molecular evidence of senescence.

CCR5+ CD8 T-cell levels and monocyte activation precede the onset of acute coronary syndrome in HIV-infected patients on antiretroviral therapy

Acute coronary syndrome (ACS) is nowadays one of the leading causes of morbid-mortality in HIV-infected population, but innate and adaptive immune mechanisms preceding this event are unknown. In this work we comprehensively and longitudinally observed, by multiparametric flow cytometry and following a case-control design, increased CCR5⁺CD8⁺ T-cells levels and monocytes expressing activation and adhesion markers in HIV-infected patients who are going to suffer ACS. In addition, we found direct associations between activated CD8⁺ T-cells and myeloid cells that were only statistically significant in the group of patients with ACS and in the follow up time point just before the ACS. Our data highlight the important role of CCR5 in the onset of ACS and suggest this receptor as a marker of cardiovascular risk and potential therapeutic target to prevent the development of such non-AIDS-related event in HIV-infected patients.

Characterization and fate of telomerase-expressing epithelia during kidney repair

After acute kidney injury, mice with short telomeres develop increased damage with reduced proliferative capacity, which suggests an important role for telomere length in kidney repair. The enzyme telomerase reverse transcriptase (mTert) regulates telomere length; embryonic stem cells and certain adult stem cells express mTert, but whether cells in the adult kidney express mTert and whether these cells play a role in renal repair are unknown. Here, we found that telomerase protein and mRNA were highly enriched in renal papilla, a proposed niche of kidney stem cells. Using mTert-GFP reporter mice, we detected mTert in a subset of papillary epithelial cells comprising the collecting duct predominantly but also the loop of Henle. Approximately 5% of mTert-GFP(+) cells were label retaining, a characteristic of stem cells. mTert mRNA levels increased in renal papilla after ischemia-reperfusion injury, but genetically labeled mTert-expressing papillary cells neither divided nor migrated out of the renal papilla during kidney repair. In summary, these data suggest that cells expressing telomerase reverse transcriptase are not a progenitor-cell population, and they do not play a direct role in kidney repair.

Serum human telomerase reverse transcriptase: a novel biomarker for breast cancer diagnosis

BACKGROUND

Telomerase is a ribonucleoprotein complex composed mainly of a reverse transcriptase catalytic subunit, telomerase reverse transcriptase (hTERT). Expression of hTERT confers telomerase activity, indicating that hTERT is the rate-limiting component of human telomerase. The aim of the present study was to investigate the diagnostic implications of hTERT in the serum of breast cancer patients.

METHODS

The study was conducted on 159 breast cancer patients and 41 healthy volunteers as controls. The evaluation of hTERT, cancer antigen 15.3 and carcinoembryonic antigen were performed by enzyme-linked immunosorbent assay, and analysed for their correlation with the patient's clinicopathological features.

RESULTS

27 of 52 (51.9%) patients with stage I breast cancer, 31 of 40 (77.5%) with stage II and 30 of 34 (88.2%) patients with stage III exhibited elevated hTERT levels. Serum hTERT levels showed significantly higher mean values in patients with breast cancer than healthy individuals. The sensitivity and specificity of hTERT in cancer diagnosis was 68.9 and 83.3%, respectively, which is significantly higher than conventional markers. The expression of serum hTERT was significantly correlated with telomerase activity in breast cancer tissues. Pretreatment serum hTERT levels showed a significant correlation with clinical stage, while correlation with nodal status and tumor size were marginal and no correlation was found with family history and age.

CONCLUSION

Serum hTERT is useful for diagnosing and assessing the clinical stage of breast cancer and is superior to conventional markers. Therefore, serum hTERT could have a potential application as a novel biomarker for breast cancer diagnosis.

Products of vitamin D3 or 7-dehydrocholesterol metabolism by cytochrome P450scc show anti-leukemia effects, having low or absent calcemic activity

Background

Cytochrome P450scc metabolizes vitamin D3 to 20-hydroxyvitamin D3 (20(OH)D3) and 20,23(OH)₂D3, as well as 1-hydroxyvitamin D3 to 1α,20-dihydroxyvitamin D3 (1,20(OH)₂D3). It also cleaves the side chain of 7-dehydrocholesterol producing 7-dehydropregnenolone (7DHP), which can be transformed to 20(OH)7DHP. UVB induces transformation of the steroidal 5,7-dienes to pregnacalciferol (pD) and a lumisterol-like compounds (pL).

Methods and Findings

To define the biological significance of these P450scc-initiated pathways, we tested the effects of their 5,7-diene precursors and secosteroidal products on leukemia cell differentiation and proliferation in comparison to 1α,25-dihydroxyvitamin D3 (1,25(OH)₂D3). These secosteroids inhibited proliferation and induced erythroid differentiation of K562 human chronic myeloid and MEL mouse leukemia cells with 20(OH)D3 and 20,23(OH)₂D3 being either equipotent or slightly less potent than 1,25(OH)₂D3, while 1,20(OH)₂D3, pD and pL compounds were slightly or moderately less potent. The compounds also inhibited proliferation and induced monocytic differentiation of HL-60 promyelocytic and U937 promonocytic human leukemia cells. Among them 1,25(OH)₂D3 was the most potent, 20(OH)D3, 20,23(OH)₂D3 and 1,20(OH)₂D3 were less active, and pD and pL compounds were the least potent. Since it had been previously proven that secosteroids without the side chain (pD) have no effect on systemic calcium levels we performed additional testing in rats and found that 20(OH)D3 had no calcemic activity at concentration as high as 1 µg/kg, whereas, 1,20(OH)₂D3 was slightly to moderately calcemic and 1,25(OH)₂D3 had strong calcemic activity.

Conclusions

We identified novel secosteroids that are excellent candidates for anti-leukemia therapy with 20(OH)D3 deserving special attention because of its relatively high potency and lack of calcemic activity.

Flow cytometric detection of human telomerase reverse transcriptase (hTERT) expression in a subpopulation of bone marrow cells

Telomerase activity has been found in most common cancers, thus indicating that telomerase detection may be a useful marker in cancer diagnosis. The telomeric amplification protocol (TRAP) assay and RT-PCR are customarily used to detect telomerase activity and the expression of the associated genes in cells. However, these methods do not provide any information about telomerase activation at an individual cell level. To analyze cells separately, those cells have to be isolated by sometimes complicated method. The immunohistochemical detection of human telomerase reverse transcriptase (hTERT) is useful to detect telomerase positive cells in a background of non-cancerous cells. A method has been developed for the detection of intranuclear hTERT protein, in a subpopulation of hematopoietic cells, using concurrent staining of a cell surface antigen and multicolor flow cytometry. Only mouse monoclonal anti-hTERT antibody demonstrated the specific positivity in immunocytochemistry and immunofluorescent flow cytometry. Human leukemia and myeloma cell lines showed 100% positivity, whereas normal neutrophils showed 0% positivity. hTERT expression was analyzed in hematopoietic precursor cells of bone marrow samples using concurrent staining of surface CD34 antigen and intracellular hTERT protein and multi-parameter flow cytometry. CD34 positive cells demonstrated higher expression of hTERT than CD34 negative cells. A quick, easy and sensitive assay for determining the hTERT protein expression has been developed. Using this method and the multi-parameter nature of flow cytometry and its ability to identify cellular subpopulations will provide a better understanding of the mechanisms regarding the activation of telomerase.

CD7(-) T cells are late memory cells generated from CD7(+) T cells

CD7(-) T cells constitute a distinct subset within the CD4(+) and CD8(+) T cell populations; their developmental and functional relationship to the majority of CD7(+) T cells, however, remained so far unresolved. We here elucidate that CD7(-) cells represent aging T cells in late memory cell development characterized by a high activation threshold, low effector capacities, and high sensitivity to activation-induced cell death (AICD). In this regard, CD7(-) T cells highly express killer cell lectin-like receptor G1 (KLRG-1), harbor telomeres of shorter lengths, a decreased telomerase expression per cell, and less amounts of T cell receptor rearrangement excision circles (TRECs) compared to CD7(+) cells. CD7(-) T cells are generated in vitro from naive CD7(+) T cells upon repetitive TCR/CD28 engagement, a process that is unidirectional and requires multiple cell divisions. Consequently, clonal expansions of CD7(-) T cells in vivo are less frequent than of CD7(+) T cells, the former can be traced back to those of CD7(+) T cells.

hTERT mRNA expression correlates with telomerase activity in human breast cancer

AIMS

Telomerase is a ribonucleoprotein enzyme that synthesises telomeres after cell division and maintains chromosomal length and stability thus leading to cellular immortalisation. hTERT (human telomerase reverse transcriptase) gene seems to be the rate-limiting determinant of telomerase reactivation. hTERT mRNA expression was reported to correlate with telomerase activity in cell lines and some human tumours. However the correlation between telomerase activity and hTERT mRNA expression has not been previously examined in human breast cancer. The present study aims to quantitatively measure the expression of hTERT mRNA and telomerase activity in human breast cancer and examine the relationship between these parameters. Furthermore the associations with other parameters including estrogen receptor (ER) and progesterone receptor (PgR) status, DNA ploidy, and S-phase fraction (SPF) are also examined.

METHODS

RNA was extracted from 18 breast carcinomas and hTERT mRNA expressions were estimated by reverse transcriptase-PCR (RT-PCR) and Taqman methodology. These tumours had already been analysed for ER and PgR status using ligand-binding assays and had had their DNA ploidy and S-phase fractions measured by flow cytometry. Telomerase activity had already been determined by using a modified telomeric repeat and amplification protocol (TRAP) assay.

RESULTS

The expression of hTERT mRNA in the breast tumours ranged between 1.3 and 2.7 x 10(7) copy numbers per micro g of cellular RNA (the median value was 2.7x10(5) and the mean was 3.1 x 10(6)). Telomerase activity was between 0 and 246 units of Total Protein Generated (TPG), where one unit of TPG was equal to 600 molecules, of telomerase substrate primers extended by at least three telomeric repeats. The median level of TPG was 60 units and the mean level was 81 units). Telomerase activity was found to significantly correlate with hTERT expression (r(s)=0.51112, P=0.0302). There was no significant correlation between hTERT and other parameters.

CONCLUSION

hTERT mRNA expression significantly correlates with telomerase activity in human breast cancer. This is consistent with the hypothesis that hTERT is the catalytic and rate-limiting determinant subunit of the enzyme.

Analysis of telomerase activity and detection of its catalytic subunit, hTERT

The discovery of the enzyme telomerase and its subunits has led to major advances in understanding the mechanisms of cellular proliferation, immortalization, aging, and neoplastic transformation. The expression of telomerase in more than 85% of tumors provides an excellent tool for the diagnosis, prognosis, and treatment of cancer. However, the techniques employed in its detection appear to play a significant role in the interpretation of the results. The telomeric repeat amplification protocol (TRAP assay) has been the standard assay in the detection of telomerase activity and many variations of this technique have been reported. Recent advances in the development of the TRAP assay and the incorporation of techniques that provide a quantitative and qualitative estimate of telomerase activity are assessed in this review. In addition to histological and cytological examination of tissues, distribution patterns of the catalytic subunit of telomerase, hTERT, are frequently used in the prognosis of tumors. The methods involved in the detection of hTERT as a biomarker of cellular transformation are also analyzed.