THE RETINOBLASTOMA PROTEIN: A MASTER TUMOR SUPPRESSOR ACTS AS A LINK BETWEEN CELL CYCLE AND CELL ADHESION

Serum Metabolomics of Retinoblastoma: Assessing the Differential Serum Metabolic Signatures of Unilateral and Bilateral Patients

Retinoblastoma (Rb) is the most common pediatric eye cancer. To identify the biomarkers for early diagnosis and monitoring the progression of Rb in patients, mapping of the alterations in their metabolic profiles is essential. The present study aims at exploring the metabolic disparity in serum from Rb patients and controls using NMR-based metabolomics. A total of 72 metabolites, including carbohydrates, amino acids, and organic acids, were quantified in serum samples from 24 Rb patients and 26 controls. Distinct clusters of Rb patients and controls were obtained using the partial least-squares discriminant analysis (PLS-DA) model. Further, univariate and multivariate analyses of unilateral and bilateral Rb patients with respect to their age-matched controls depicted their distinct metabolic fingerprints. Metabolites including 2-phosphoglycerate, 4-aminobutyrate, proline, O-phosphocholine, O-phosphoethanolamine, and Sn-glycero-3-phosphocholine (Sn-GPC) showed significant perturbation in both unilateral and bilateral Rb patients. However, metabolic differences among the bilateral Rb cases were more pronounced than those in unilateral Rb cases with respect to controls. In addition to major discriminatory metabolites for Rb, unilateral and bilateral Rb cases showed specific metabolic changes, which might be the result of their differential genetic/somatic mutational backgrounds. This further suggests that the aberrant metabolic perturbation in bilateral patients signifies the severity of the disease in Rb patients. The present study demonstrated that identified serum metabolites have potential to serve as a noninvasive method for detection of Rb, discriminate bilateral from unilateral Rb patients, and aid in better understanding of the RB tumor biology.

Tumor collagens predict genetic features and patient outcomes

The extracellular matrix (ECM) is a critical determinant of tumor fate that reflects the output from myriad cell types in the tumor. Collagens constitute the principal components of the tumor ECM. The changing collagen composition in tumors along with their impact on patient outcomes and possible biomarkers remains largely unknown. The RNA expression of the 43 collagen genes from solid tumors in The Cancer Genome Atlas (TCGA) was clustered to classify tumors. PanCancer analysis revealed how collagens by themselves can identify the tissue of origin. Clustering by collagens in each cancer type demonstrated strong associations with survival, specific immunoenvironments, somatic gene mutations, copy number variations, and aneuploidy. We developed a machine learning classifier that predicts aneuploidy, and chromosome arm copy number alteration (CNA) status based on collagen expression alone with high accuracy in many cancer types with somatic mutations, suggesting a strong relationship between the collagen ECM context and specific molecular alterations. These findings have broad implications in defining the relationship between cancer-related genetic defects and the tumor microenvironment to improve prognosis and therapeutic targeting for patient care, opening new avenues of investigation to define tumor ecosystems.

The Association between Race/Ethnicity and Cancer Stage at Diagnosis of Bone Malignancies: A Retrospective Cohort Study

INTRODUCTION AND OBJECTIVE

Limited data exists analyzing disparities in diagnosis regarding primary bone neoplasms (PBN). The objective of our study was to determine if there is an association between race/ethnicity and advanced stage of diagnosis of PBN.

METHODS

This population-based retrospective cohort study included patient demographic and health information extracted from the National Cancer Institute Surveillance, Epidemiology, and End Results Program (SEER). The main exposure variable was race/ethnicity categorized as non-Hispanic white (NH-W), non-Hispanic black (NH-B), non-Hispanic Asian Pacific Islander (NH-API), and Hispanic. The main outcome variable was advanced stage at diagnosis. Age, sex, tumor grade, type of bone cancer, decade, and geographic location were co-variates. Unadjusted and adjusted logistic regression analyses were conducted calculating odds ratios (OR) and corresponding 95% confidence intervals.

RESULTS

Race/ethnicity was not statistically significantly associated with advanced-stage disease. Adjusted OR for NH-B was 0.94 (95% CI: 0.78-1.38), for NH-API 1.07 (95% CI: 0.86-1.33) and for Hispanic 1.03 (95% CI: 0.85-1.25).

CONCLUSIONS

The lack of association between race and advanced stage of disease could be due to high availability and low cost for initial management of bone malignancies though plain radiographs. Future studies may include socioeconomic status and insurance coverage as covariates in the analysis.

Single-Cell Transcriptomics Reveals the Expression of Aging- and Senescence-Associated Genes in Distinct Cancer Cell Populations

The human aging process is associated with molecular changes and cellular degeneration, resulting in a significant increase in cancer incidence with age. Despite their potential correlation, the relationship between cancer- and ageing-related transcriptional changes is largely unknown. In this study, we aimed to analyze aging-associated transcriptional patterns in publicly available bulk mRNA-seq and single-cell RNA-seq (scRNA-seq) datasets for chronic myelogenous leukemia (CML), colorectal cancer (CRC), hepatocellular carcinoma (HCC), lung cancer (LC), and pancreatic ductal adenocarcinoma (PDAC). Indeed, we detected that various aging/senescence-induced genes (ASIGs) were upregulated in malignant diseases compared to healthy control samples. To elucidate the importance of ASIGs during cell development, pseudotime analyses were performed, which revealed a late enrichment of distinct cancer-specific ASIG signatures. Notably, we were able to demonstrate that all cancer entities analyzed in this study comprised cell populations expressing ASIGs. While only minor correlations were detected between ASIGs and transcriptome-wide changes in PDAC, a high proportion of ASIGs was induced in CML, CRC, HCC, and LC samples. These unique cellular subpopulations could serve as a basis for future studies on the role of aging and senescence in human malignancies.

Understanding the Radiobiology of Vestibular Schwannomas to Overcome Radiation Resistance

Vestibular schwannomas (VS) are benign tumors arising from cranial nerve VIII that account for 8-10% of all intracranial tumors and are the most common tumors of the cerebellopontine angle. These tumors are typically managed with observation, radiation therapy, or microsurgical resection. Of the VS that are irradiated, there is a subset of tumors that are radioresistant and continue to grow; the mechanisms behind this phenomenon are not fully understood. In this review, the authors summarize how radiation causes cellular and DNA injury that can activate (1) checkpoints in the cell cycle to initiate cell cycle arrest and DNA repair and (2) key events that lead to cell death. In addition, we discuss the current knowledge of VS radiobiology and how it may contribute to clinical outcomes. A better understanding of VS radiobiology can help optimize existing treatment protocols and lead to new therapies to overcome radioresistance.

Differential expression of αVβ3 and αVβ6 integrins in prostate cancer progression

Neuroendocrine prostate cancer (NEPrCa) arises de novo or after accumulation of genomic alterations in pre-existing adenocarcinoma tumors in response to androgen deprivation therapies. We have provided evidence that small extracellular vesicles released by PrCa cells and containing the αVβ3 integrin promote neuroendocrine differentiation of PrCa in vivo and in vitro. Here, we examined αVβ3 integrin expression in three murine models carrying a deletion of PTEN (SKO), PTEN and RB1 (DKO), or PTEN, RB1 and TRP53 (TKO) genes in the prostatic epithelium; of these three models, the DKO and TKO tumors develop NEPrCa with a gene signature comparable to those of human NEPrCa. Immunostaining analysis of SKO, DKO and TKO tumors shows that αVβ3 integrin expression is increased in DKO and TKO primary tumors and metastatic lesions, but absent in SKO primary tumors. On the other hand, SKO tumors show higher levels of a different αV integrin, αVβ6, as compared to DKO and TKO tumors. These results are confirmed by RNA-sequencing analysis. Moreover, TRAMP mice, which carry NEPrCa and adenocarcinoma of the prostate, also have increased levels of αVβ3 in their NEPrCa primary tumors. In contrast, the αVβ6 integrin is only detectable in the adenocarcinoma areas. Finally, analysis of 42 LuCaP patient-derived xenografts and primary adenocarcinoma samples shows a positive correlation between αVβ3, but not αVβ6, and the neuronal marker synaptophysin; it also demonstrates that αVβ3 is absent in prostatic adenocarcinomas. In summary, we demonstrate that αVβ3 integrin is upregulated in NEPrCa primary and metastatic lesions; in contrast, the αVβ6 integrin is confined to adenocarcinoma of the prostate. Our findings suggest that the αVβ3 integrin, but not αVβ6, may promote a shift in lineage plasticity towards a NE phenotype and might serve as an informative biomarker for the early detection of NE differentiation in prostate cancer.

Octopus vulgaris ink extracts exhibit antioxidant, antimutagenic, cytoprotective, antiproliferative, and proapoptotic effects in selected human cancer cell lines

Cancer is a noncommunicable disease of rising worldwide concern. Marine food products such as Octopus vulgaris ink (OI) could be sources of compounds addressing these concerns. This study aimed to evaluate the antimutagenic, cytoprotective, antiproliferative, proapoptotic, and antioxidant capacity of OI extracts on human cancer cell lines (22Rv1, HeLa, A549). The ARPE-19 cell line was used as a reference human cell line to evaluate the ink's cytotoxicity. The water extract exhibited the highest antimutagenic and cytoprotective effect, but the dichloromethane extract (DM) showed the lowest half lethal concentration against 22Rv1 cells. Structural elucidation of purified DM fractions (F1, F2, F3) identified an unreported compound, N-(2-ozoazepan-3-yl)-pyrrolidine-2-carboxamide (OPC). DM-F2 showed high antiproliferative effect (LC₅₀ = 27.6 µg/mL), reactive species modulation, early-apoptosis induction (42.9%), and nuclei disruption in 22Rv1 cells. In silico analysis predicted high OPC affinity with Cyclin D1 (-6.70 kcal/mol), suggesting its potential impact on cell cycle arrest. These results highlight the antimutagenic, cytoprotective, and antiproliferative potential health benefits derived from underutilized marine food products such as OI. Further investigations at in vitro or in vivo levels are required to elucidate mechanisms and health benefits from OI. PRACTICAL APPLICATION: O. vulgaris ink is an underutilized marine natural product that could be a source of biological compounds with potential health benefits such as antioxidant activity and cancer prevention.

Motifs enable communication efficiency and fault-tolerance in transcriptional networks

Analysis of the topology of transcriptional regulatory networks (TRNs) is an effective way to study the regulatory interactions between the transcription factors (TFs) and the target genes. TRNs are characterized by the abundance of motifs such as feed forward loops (FFLs), which contribute to their structural and functional properties. In this paper, we focus on the role of motifs (specifically, FFLs) in signal propagation in TRNs and the organization of the TRN topology with FFLs as building blocks. To this end, we classify nodes participating in FFLs (termed motif central nodes) into three distinct roles (namely, roles A, B and C), and contrast them with TRN nodes having high connectivity on the basis of their potential for information dissemination, using metrics such as network efficiency, path enumeration, epidemic models and standard graph centrality measures. We also present the notion of a three tier architecture and how it can help study the structural properties of TRN based on connectivity and clustering tendency of motif central nodes. Finally, we motivate the potential implication of the structural properties of motif centrality in design of efficient protocols of information routing in communication networks as well as their functional properties in global regulation and stress response to study specific disease conditions and identification of drug targets.

Proteomic Profiling of Retinoblastoma-Derived Exosomes Reveals Potential Biomarkers of Vitreous Seeding

Retinoblastoma (RB) is the most common tumor of the eye in early childhood. Although recent advances in conservative treatment have greatly improved the visual outcome, local tumor control remains difficult in the presence of massive vitreous seeding. Traditional biopsy has long been considered unsafe in RB, due to the risk of extraocular spread. Thus, the identification of new biomarkers is crucial to design safer diagnostic and more effective therapeutic approaches. Exosomes, membrane-derived nanovesicles that are secreted abundantly by aggressive tumor cells and that can be isolated from several biological fluids, represent an interesting alternative for the detection of tumor-associated biomarkers. In this study, we defined the protein signature of exosomes released by RB tumors (RBT) and vitreous seeding (RBVS) primary cell lines by high resolution mass spectrometry. A total of 5666 proteins were identified. Among these, 5223 and 3637 were expressed in exosomes RBT and one RBVS group, respectively. Gene enrichment analysis of exclusively and differentially expressed proteins and network analysis identified in RBVS exosomes upregulated proteins specifically related to invasion and metastasis, such as proteins involved in extracellular matrix (ECM) remodeling and interaction, resistance to anoikis and the metabolism/catabolism of glucose and amino acids.

Hyper-phosphorylation of Rb S249 together with CDK5R2/p39 overexpression are associated with impaired cell adhesion and epithelial-to-mesenchymal transition: Implications as a potential lung cancer grading and staging biomarker

Prediction of lung cancer metastasis relies on post-resection assessment of tumor histology, which is a severe limitation since only a minority of lung cancer patients are diagnosed with resectable disease. Therefore, characterization of metastasis-predicting biomarkers in pre-resection small biopsy specimens is urgently needed. Here we report a biomarker consisting of the phosphorylation of the retinoblastoma protein (Rb) on serine 249 combined with elevated p39 expression. This biomarker correlates with epithelial-to-mesenchymal transition traits in non-small cell lung carcinoma (NSCLC) cells. Immunohistochemistry staining of NSCLC tumor microarrays showed that strong phospho-Rb S249 staining positively correlated with tumor grade specifically in the squamous cell carcinoma (SCC) subtype. Strong immunoreactivity for p39 positively correlated with tumor stage, lymph node invasion, and distant metastases, also in SCC. Linear regression analyses showed that the combined scoring for phospho-Rb S249, p39 and E-cadherin in SCC is even more accurate at predicting tumor staging, relative to each score individually. We propose that combined immunohistochemistry staining of NSCLC samples for Rb phosphorylation on S249, p39, and E-cadherin protein expression could aid in the assessment of tumor staging and metastatic potential when tested in small primary tumor biopsies. The intense staining for phospho-Rb S249 that we observed in high grade SCC could also aid in the precise sub-classification of poorly differentiated SCCs.

Rab18 overexpression promotes proliferation and chemoresistance through regulation of mitochondrial function in human gastric cancer

Background

Dysregulation of Rab18 has been implicated in human cancers. However, its clinical significance and biological function in gastric cancer have not been investigated.

Methods

We examined Rab18 expression in gastric cancer tissues using immunohistochemistry. We used SNU-1 and AGS cell lines for plasmid and siRNA transfection respectively. MTT, colony formation assay, cell cycle analysis, matrigel invasion, wound healing assay, AnnexinV/PI analysis and western blotting were used to examine the biological effect and mechanism of Rab18 in gastric cancer cell lines.

Results

Rab18 protein expression was upregulated in gastric cancer tissues and this correlated with advanced stage and poor prognosis. Rab18 overexpression promoted proliferation in vitro and in vivo. Cell cycle analysis showed that Rab18 overexpression upregulated, while its depletion downregulated S phase percentage. Matrigel invasion and wound healing assays indicated that Rab18 positively regulated SNU-1 cell invasion and migration while its knockdown inhibited AGS cell invasion and migration. Rab18 maintained cell viability and downregulated apoptosis after cisplatin treatment, with upregulated mitochondrial membrane potential and downregulated mitochondrial reactive oxygen species (ROS) production. Rab18 overexpression upregulated p-Rb, survivin while downregulated cytochrome c, cleaved caspase-3 and cleaved PARP.

Conclusion

In conclusion, our results indicate that Rab18 promoted gastric cancer growth and chemoresistance, possibly through regulation of mitochondrial function and survivin.

Polymorphic variability in the exon 19 of the RB1 gene and its flanking intronic sequences in HPV16-associated precancerous lesions in the Greek population

PURPOSE

The tumour suppressor protein RB plays a decisive role in negative control of the cell cycle, inhibiting tumour development. The present analysis investigated the prevalence of the nucleotide polymorphism A153104G, which is located at intron 18 of the RB1 gene, and investigated the impact of the polymorphic variability in the exon 19 and its flanking intronic sequences on the severity of cervical disease in HPV16-positive Greek women.

METHODOLOGY

The nucleotide polymorphism A153104G was detected by PCR-RFLP assay, while the amplicons were further subjected to cloning and sequencing. Moreover, molecular evolutionary analysis was performed using the maximum-likelihood (ML) and empirical Bayesian (EB) methods in order to evaluate the selective pressure acting on exon 19 of the RB1 gene.Results/Key findings. The A153104G nucleotide polymorphism was only detected in one control case. Moreover, sequence analysis of the amplicons revealed that the polymorphic variability in the RB1 gene increased with the severity of the cervical dysplasia. The link between the observed polymorphic variability and the progress of cervical disease was reflected in the molecular evolutionary analysis that was performed on the exon 19 of the RB1 gene, since negative selective pressure was acting upon exon 19 in the control and low-grade squamous intraepithelial lesion (LSIL) cervical samples, while positive selective pressure was acting upon exon 19 in the high-grade squamous intraepithelial lesion (HSIL) specimens.

CONCLUSIONS

The A153104G nucleotide polymorphism did not emerge as a potential biomarker for the development of precancerous lesions in the Greek patients, while the accumulation of sequence variations in RB1 gene might influence patients' susceptibility towards the progression of cervical neoplasia.

Rab14 overexpression regulates gemcitabine sensitivity through regulation of Bcl-2 and mitochondrial function in pancreatic cancer

Rab family protein Rab14 has been implicated in the development of human cancers. To date, its expression pattern, biological function, and potential mechanism in pancreatic cancer have not been explored. In this study, we analyzed Rab14 expression in 103 cases of pancreatic cancer tissues using immunohistochemistry (IHC) and found that Rab14 was overexpressed in 41/103 cases (39.8%). Rab14 overexpression correlated with the advanced stage. Moreover, elevated Rab14 levels indicated poor prognosis of patients with pancreatic cancers. We used BxPC-3 and Capan-2 respectively for plasmid and siRNA transfection. MTT and colony formation assays showed that Rab14 transfection increased cell proliferation and colony formation in BxPC-3 cells. Rab14 siRNA knockdown inhibits proliferation and colony formation ability in Capan-2 cell line. Cell cycle analysis showed that Rab14 facilitated cell cycle progression. Matrigel invasion assay showed that Rab14 promoted BxPC-3 cell invasion while its depletion inhibited Capan-2 cell invasion. In addition, MTT and AnnexinV/PI analysis demonstrated that overexpression of Rab14 reduced gemcitabine sensitivity which conversely was increased by Rab14 knockdown. We also demonstrated that Rab14 upregulated mitochondrial membrane potential (MMP) while its depletion downregulated MMP during gemcitabine treatment. In addition, western blotting revealed that Rab14 overexpression upregulated cyclin D1, cyclin A, cyclin E, p-Rb, and Bcl-2 and downregulated p21. Rab14 also downregulated caspase3, PARP cleavage, and cytochrome c release. In conclusion, our data indicated that Rab14 was overexpressed in pancreatic cancer and promotes growth and gemcitabine resistance, possibly through regulation of mitochondrial function and Bcl-2.

The Retinoblastoma (RB) Tumor Suppressor: Pushing Back against Genome Instability on Multiple Fronts

The retinoblastoma (RB) tumor suppressor is known as a master regulator of the cell cycle. RB is mutated or functionally inactivated in the majority of human cancers. This transcriptional regulator exerts its function in cell cycle control through its interaction with the E2F family of transcription factors and with chromatin remodelers and modifiers that contribute to the repression of genes important for cell cycle progression. Over the years, studies have shown that RB participates in multiple processes in addition to cell cycle control. Indeed, RB is known to interact with over 200 different proteins and likely exists in multiple complexes. RB, in some cases, acts through its interaction with E2F1, other members of the pocket protein family (p107 and p130), and/or chromatin remodelers and modifiers. RB is a tumor suppressor with important chromatin regulatory functions that affect genomic stability. These functions include the role of RB in DNA repair, telomere maintenance, chromosome condensation and cohesion, and silencing of repetitive regions. In this review we will discuss recent advances in RB biology related to RB, partner proteins, and their non-transcriptional functions fighting back against genomic instability.

Interrogating the Roles of Post-Translational Modifications of Non-Histone Proteins

Post-translational modifications (PTMs) allot versatility to the biological functions of highly conserved proteins. Recently, modifications to non-histone proteins such as methylation, acetylation, phosphorylation, glycosylation, ubiquitination, and many more have been linked to the regulation of pivotal pathways related to cellular response and stability. Due to the roles these dynamic modifications assume, their dysregulation has been associated with cancer and many other important diseases such as inflammatory disorders and neurodegenerative diseases. For this reason, we present a review and perspective on important post-translational modifications on non-histone proteins, with emphasis on their roles in diseases and small molecule inhibitors developed to target PTM writers. Certain PTMs' contribution to epigenetics has been extensively expounded; yet more efforts will be needed to systematically dissect their roles on non-histone proteins, especially for their relationships with nononcological diseases. Finally, current research approaches for PTM study will be discussed and compared, including limitations and possible improvements.