Telomere length regulation through epidermal growth factor receptor signaling in cancer

Insight into telomere regulation: road to discovery and intervention in plasma drug-protein targets

BACKGROUND

Telomere length is a critical metric linked to aging, health, and disease. Currently, the exploration of target proteins related to telomere length is usually limited to the context of aging and specific diseases, which limits the discovery of more relevant drug targets. This study integrated large-scale plasma cis-pQTLs data and telomere length GWAS datasets. We used Mendelian randomization(MR) to identify drug target proteins for telomere length, providing essential clues for future precision therapy and targeted drug development.

METHODS

Using plasma cis-pQTLs data from a previous GWAS study (3,606 Pqtls associated with 2,656 proteins) and a GWAS dataset of telomere length (sample size: 472,174; GWAS ID: ieu-b-4879) from UK Biobank, using MR, external validation, and reverse causality testing, we identified essential drug target proteins for telomere length. We also performed co-localization, Phenome-wide association studies and enrichment analysis, protein-protein interaction network construction, search for existing intervening drugs, and potential drug/compound prediction for these critical targets to strengthen and expand our findings.

RESULTS

After Bonferron correction (p < 0.05/734), RPN1 (OR: 0.96; 95%CI: (0.95, 0.97)), GDI2 (OR: 0.94; 95%CI: (0.92, 0.96)), NT5C (OR: 0.97; 95%CI: (0.95, 0.98)) had a significant negative causal association with telomere length; TYRO3 (OR: 1.11; 95%CI: (1.09, 1.15)) had a significant positive causal association with telomere length. GDI2 shared the same genetic variants with telomere length (coloc.abf-PPH 4 > 0.8).

CONCLUSION

Genetically determined plasma RPN1, GDI2, NT5C, and TYRO3 have significant causal effects on telomere length and can potentially be drug targets. Further exploration of the role and mechanism of these proteins/genes in regulating telomere length is needed.

Evaluation of the Impact of Alternanthera philoxeroides (Mart.) Griseb. Extract on Memory Impairment in D-Galactose-Induced Brain Aging in Mice through Its Effects on Antioxidant Enzymes, Neuroinflammation, and Telomere Shortening

Aging is a well-known factor that accelerates brain deterioration, resulting in impaired learning and memory functions. This current study evaluated the potential of an extract of Alternanthera philoxeroides (AP), an edible flavonoid-rich plant, to ameliorate D-galactose-induced brain aging in male mice. Chronic administration of D-galactose (150 mg/kg/day) in mice mimicked the characteristics of aging by accelerating senescence via downregulation of the following telomere-regulating factors: mouse telomerase reverse transcriptase (mTERT) and mouse telomeric repeat-binding factors 1 (mTRF1) and 2 (mTRF2). D-galactose also decreased the activities of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), while increasing expression of neuroinflammatory cytokines in the frontal cortex and hippocampus. Daily treatment of D-galactose-induced aging mice with AP at 250 and 500 mg/kg/day or vitamin E (100 mg/kg/day) significantly increased the activities of SOD and CAT, as well as expression of mTERT, mTRF1, and mTRF2, which are involved in telomere stabilization, but decreased the levels of proinflammatory cytokines IL-1β, IL-6, and TNF-α. In the behavioral portion of the study, AP improved aging-related cognitive deficits in short-term memory as shown by the Y-maze task and the novel object recognition test (NORT) and long-term memory as shown by the Morris water maze test (MWMT). The flavones kaempferol-O-glucoside (1), quercetin (2), alternanthin B (3), demethyltorosaflavone D (4), and chrysoeriol-7-O-rhamnoside (5), which could be responsible for the observed effects of AP in the D-galactose-induced aging mice, were identified by HPLC analysis.

Telomerase: A prominent oncological target for development of chemotherapeutic agents

Telomerase is a ribonucleoprotein (RNP) responsible for the maintenance of chromosomal integrity by stabilizing telomere length. Telomerase is a widely expressed hallmark responsible for replicative immortality in 80-90% of malignant tumors. Cancer cells produce telomerase which prevents telomere shortening by adding telomeres sequences beyond Hayflick's limit; which enables them to divide uncontrollably. The activity of telomerase is relatively low in somatic cells and absent in normal cells, but the re-activation of this RNP in normal cells suppresses p53 activity which leads to the avoidance of senescence causing malignancy. Here, we have focused explicitly on various anti-telomerase therapies and telomerase-inhibiting molecules for the treatment of cancer. We have covered molecules that are reported in developmental, preclinical, and clinical trial stages as potent telomerase inhibitors. Apart from chemotherapy, we have also included details of immunotherapy, gene therapy, G-quadruplex stabilizers, and HSP-90 inhibitors. The purpose of this work is to discuss the challenges behind the development of novel telomerase inhibitors and to identify various perspectives for designing anti-telomerase compounds.

Antitumor efficacy of a recombinant EGFR-targeted fusion protein conjugate that induces telomere shortening and telomerase downregulation

OBJECTIVE

To prepare a recombinant EGFR-targeted fusion protein drug conjugate acting on telomere and telomerase; and evaluate its antitumor efficacy.

METHODS

We prepared a recombinant fusion protein Fv-LDP-D3 which consists of the Fv fragment of an anti-EGFR monoclonal antibody (MAb), the apoprotein of lidamycin (LDP), and the third domain (D3) of human serum albumin (HSA); then generated the conjugate Fv-LDP-D3∼AE by integrating the active enediyne chomophore (AE) of lidamycin. Accordingly, in vitro and in vivo experiments were performed.

RESULTS

As shown, Fv-LDP-D3 specifically bound to EGFR highly-expressing cancer cells and intensely entered K-Ras mutant cells via enhanced macropinocytosis. By in vivo imaging, Fv-LDP-D3 displayed intense accumulation and persistent retention in tumor-site. Furthermore, the conjugate Fv-LDP-D3∼AE displayed highly potent cytotoxicity to cancer cells with IC₅₀ at 0.1 nM level. The conjugate induced telomere shortening and downregulation of telomerase and EGFR pathway related proteins. Fv-LDP-D3∼AE exhibited prominent antitumor efficacy against human colorectal cancer xenograft accompanying with significant increase of serum IFN-β in athymic mice.

CONCLUSION

The recombinant fusion protein conjugate that exhibits the capability of tumor-targeting drug delivery can induce telomere shortening and telomerase downregulation. The investigation may lay the foundation for the development of MAb-HSA domain-based fusion protein drug conjugates.

The relationship between n-3 polyunsaturated fatty acids and telomere: A review on proposed nutritional treatment against metabolic syndrome and potential signaling pathways

Metabolic syndrome (MetS), a cluster of metabolic abnormalities composed of central obesity, elevated blood pressure, glucose disturbances, hypercholesterolemia and dyslipidaemia, has increasingly become a public health problem in the 21st century worldwide. The dysfunction of telomeres, the repetitive DNA with highly conserved sequences (5'-TTAGGG-3'), is remarkably correlated with organismal aging, even suggesting a causal relationship with metabolic disorders. The health benefits of n-3 polyunsaturated fatty acids (PUFAs) in multiple disorders are associated with telomere length in evidence, which have recently drawn wide attention. However, functional targets and pathways for the associations of n-3 PUFAs and telomere with MetS remain scare. Few studies have summarized the role of n-3 PUFAs in DNA damage repair pathways, anti-inflammatory pathways, and redox balance, linking with telomere biology, and other potential telomere-related signaling pathways. This review aims to (i) elucidate how n-3 PUFAs ameliorate telomere attrition in the context of anti-oxidation and anti-inflammation; (ii) unravel the role of n-3 PUFAs in modulating telomere-related neuron dysfunction and regulating the neuro-endocrine-immunological network in MetS; (iii) epidemiologically implicate the associations of metabolic disorders and n-3 PUFAs with telomere length; and (iv) suggest promising biochemical approaches and advancing methodologies to overcome the inter-variation problem helpful for future research.

Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer

Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.

Phasing analysis of lung cancer genomes using a long read sequencer

Chromosomal backgrounds of cancerous mutations still remain elusive. Here, we conduct the phasing analysis of non-small cell lung cancer specimens of 20 Japanese patients. By the combinatory use of short and long read sequencing data, we obtain long phased blocks of 834 kb in N50 length with >99% concordance rate. By analyzing the obtained phasing information, we reveal that several cancer genomes harbor regions in which mutations are unevenly distributed to either of two haplotypes. Large-scale chromosomal rearrangement events, which resemble chromothripsis events but have smaller scales, occur on only one chromosome, and these events account for the observed biased distributions. Interestingly, the events are characteristic of EGFR mutation-positive lung adenocarcinomas. Further integration of long read epigenomic and transcriptomic data reveal that haploid chromosomes are not always at equivalent transcriptomic/epigenomic conditions. Distinct chromosomal backgrounds are responsible for later cancerous aberrations in a haplotype-specific manner.

Telomere Signaling and Maintenance Pathways in Spermatozoa of Infertile Men Treated With Antioxidants: An in silico Approach Using Bioinformatic Analysis

Telomere shortening is considered as a marker of cellular senescence and it is regulated by various signaling pathways. Sperm telomere appears to play important role in its longevity and function. Antioxidant intake has been known to prevent the shortening of telomere. In the management of male infertility, antioxidants are commonly used to counterbalance the seminal oxidative stress. It is important to understand how antioxidants treatment may modulate telomere signaling in sperm. In the current study, we have identified 377 sperm proteins regulated by antioxidants based on data mining of published literature. Bioinformatic analysis revealed involvement of 399 upstream regulators and 806 master regulators associated with differentially expressed sperm proteins. Furthermore, upstream regulator analysis indicated activation of kinases (EGFR and MAPK3) and transcription factors (CCNE1, H2AX, MYC, RB1, and TP53). Hence, it is evident that antioxidant supplementation activates molecules associated with telomere function in sperm. The outcome of this in silico study suggests that antioxidant therapy has beneficial effects on certain transcription factors and kinases associated with sperm telomere maintenance and associated signaling pathways that may play an important role in the management of male factor infertility.

Novel Prognostic Biomarkers in Metastatic and Locally Advanced Colorectal Cancer: Micronuclei Frequency and Telomerase Activity in Peripheral Blood Lymphocytes

PURPOSE

Due to the current practice on colorectal cancer (CRC) management, chemoresistance is most often recognized at the end of the treatment. Therefore, effective and easy-to-use prognostic biomarkers are needed.

EXPERIMENTAL DESIGN

We evaluated the prognostic significance of two novel CRC biomarkers: a) micronuclei frequency (MNf) in 55 metastatic CRC (mCRC) and 21 locally advanced rectal cancer (laRC) patients using cytokinesis block micronucleus assay (CBMN assay) and b) telomerase activity (TA) in 23 mCRC and five laRC patients using TRAP-ELISA. Both biomarkers were evaluated in peripheral blood lymphocytes (PBLs) before, at the middle, and at the end of the therapy (approximately 0, 3, and 6 months) for mCRC patients before, at the end of the therapy, and after surgery for laRC patients.

RESULTS

Overall, MNf demonstrated significant prognostic value since a decrease of MNf less than 29% between middle and initial MNf measurements can discriminate between progressive and stable/responsive disease with sensitivity of 36% and specificity of 87.0% while being able to identify responsive disease with sensitivity of 72.7% and specificity of 59.3%. On the other hand, TA presented a significant trend of increase (p = 0.07) in patients with progressive disease at the middle measurement.

CONCLUSIONS

The findings of this study suggest that the MN frequency may serve as a promising prognostic biomarker for the monitoring of the treatment response of patients with CRC, while TA should be evaluated in a larger group of patients to further validate its significance.

Heterogeneous Nuclear Ribonucleoproteins Involved in the Functioning of Telomeres in Malignant Cells

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are structurally and functionally distinct proteins containing specific domains and motifs that enable the proteins to bind certain nucleotide sequences, particularly those found in human telomeres. In human malignant cells (HMCs), hnRNP-A1-the most studied hnRNP-is an abundant multifunctional protein that interacts with telomeric DNA and affects telomerase function. In addition, it is believed that other hnRNPs in HMCs may also be involved in the maintenance of telomere length. Accordingly, these proteins are considered possible participants in the processes associated with HMC immortalization. In our review, we discuss the results of studies on different hnRNPs that may be crucial to solving molecular oncological problems and relevant to further investigations of these proteins in HMCs.

The role of p21/CIP1/WAF1 (p21) in the negative regulation of the growth hormone/growth hormone receptor and epidermal growth factor/epidermal growth factor receptor pathways, in growth hormone transduction defect

PURPOSE

Growth hormone transduction defect (GHTD) is characterized by severe short stature, impaired STAT3 (signal transducer and activator of transcription-3) phosphorylation and overexpression of the cytokine inducible SH2 containing protein (CIS) and p21/CIP1/WAF1. To investigate the role of p21/CIP1/WAF1 in the negative regulation of the growth hormone (GH)/GH receptor and Epidermal Growth Factor (EGF)/EGF Receptor pathways in GHTD.

METHODS

Fibroblast cultures were developed from gingival biopsies of 1 GHTD patient and 1 control. The protein expression and the cellular localization of p21/CIP1/WAF1 was studied by Western immunoblotting and immunofluorescence, respectively: at the basal state and after induction with 200-μg/L human GH (hGH) (GH200), either with or without siRNA CIS (siCIS); at the basal state and after inductions with 200-μg/L hGH (GH200), 1,000-μg/L hGH (GH1000) or 50-ng/mL EGF.

RESULTS

After GH200/siCIS, the protein expression and nuclear localization of p21 were reduced in the patient. After successful induction of GH signaling (control, GH200; patient, GH1000), the protein expression and nuclear localization of p21 were reduced. After induction with EGF, p21 translocated to the cytoplasm in the control, whereas in the GHTD patient it remained located in the nucleus.

CONCLUSION

In the GHTD fibroblasts, when CIS is reduced, either after siCIS or after a higher dose of hGH (GH1000), p21's antiproliferative effect (nuclear localization) is also reduced and GH signaling is activated. There also appears to be a positive relationship between the 2 inhibitors of GH signaling, CIS and p21. Finally, in GHTD, p21 seems to participate in the regulation of both the GH and EGF/EGFR pathways, depending upon its cellular location.