Troponin-I enhances and is required for oncogenic overgrowth

Discovery and Characteristics of a Novel Antitumor Cyclopeptide Derived from Shark

Peptides pose a challenge in drug development due to their short half-lives in vivo. In this study, we conducted in vitro degradation experiments on SAIF, which is a shark-derived peptide that we previously studied. The degradation fragments were sequenced and a truncated peptide sequence was identified. The truncated peptide was then cloned and expressed via the E. coli system with traceless cloning to form a novel cyclic peptide in vitro oxidation condition via the formation of a disulfide bond between the N- and C-termini, which was named ctSAIF. ctSAIF exhibited high anti-HCC activity and enhanced enzymatic stability in vitro, and retained antitumor activity and good biocompatibility in systemic circulation in a HCC xenograft model. Our study discovered and characterized a novel shark-derived cyclic peptide with antitumor activity, laying a foundation for its further development as an antitumor drug candidate. The study also provided a new solution for peptide drug development.

Overexpression of the PTEN Gene in Myocardial Tissues of Coronary Bypass Surgery Patients

BACKGROUND

Coronary artery disease is a complex disorder that causes death worldwide. One of the genes involved in developing this disease may be PTEN.

OBJECTIVES

This study aimed to investigate the PTEN gene and protein expression in tissue and blood samples taken from coronary bypass surgery patients.

METHODS

Molecular studies were performed at Erciyes University Genome and Stem Cell Center (GENKOK). Right atrial appendage and blood samples were taken from the central vein of 22 coronary bypass surgery patients before starting and ending cardiopulmonary bypass. PTEN expression was determined using quantitative real-time PCR and western blot analysis. The significance level was accepted as p<0.05.

RESULTS

There was no significant difference in the PTEN gene expression in blood samples taken before and after cardiopulmonary bypass. However, a substantial increase in both protein and gene expression levels of P-PTEN and PTEN was observed in the tissue samples. Myocardial expression of the PTEN gene was significantly increased at the end of the cardiopulmonary bypass. PTEN gene expression in the post-cardiopulmonary bypass period was increased when compared to the pre-bypass period, but it was insignificant when compared to healthy controls.

CONCLUSION

This study first revealed the role of the PTEN gene by analyzing both mRNA and protein expression in coronary bypass patients, appearing in both myocardial tissue and blood samples. Increased levels of PTEN may be a marker in myocardial tissue for patients with coronary artery disease.

Synaptic components are required for glioblastoma progression in Drosophila

Glioblastoma (GB) is the most aggressive, lethal and frequent primary brain tumor. It originates from glial cells and is characterized by rapid expansion through infiltration. GB cells interact with the microenvironment and healthy surrounding tissues, mostly neurons and vessels. GB cells project tumor microtubes (TMs) contact with neurons, and exchange signaling molecules related to Wingless/WNT, JNK, Insulin or Neuroligin-3 pathways. This cell to cell communication promotes GB expansion and neurodegeneration. Moreover, healthy neurons form glutamatergic functional synapses with GB cells which facilitate GB expansion and premature death in mouse GB xerograph models. Targeting signaling and synaptic components of GB progression may become a suitable strategy against glioblastoma. In a Drosophila GB model, we have determined the post-synaptic nature of GB cells with respect to neurons, and the contribution of post-synaptic genes expressed in GB cells to tumor progression. In addition, we document the presence of intratumoral synapses between GB cells, and the functional contribution of pre-synaptic genes to GB calcium dependent activity and expansion. Finally, we explore the relevance of synaptic genes in GB cells to the lifespan reduction caused by GB advance. Our results indicate that both presynaptic and postsynaptic proteins play a role in GB progression and lethality.

Glioblastoma (GB) is the most frequent and aggressive type of brain tumor. It is originated from glial cells that expand and proliferate very fast in the brain. GB cells infiltrate and establish cell to cell communication with healthy neurons. Currently there is no effective treatment for GB and these tumors result incurable with an average survival of 16 months after diagnosis. Here we used a Drosophila melanogaster model to search for genetic suppressors of GB progression. The results show that genes involved in the formation of synapses are required for glial cell number increase, expansion of tumoral volume and premature death. Among these synaptic genes we found that post-synaptic genes that contribute to Neuron-GB interaction which validate previous findings in human GB. Moreover, we found electro dense structures between GB cells that are compatible with synapses and that expression of pre-synaptic genes, including brp, Lip-α and syt 1, is required for GB progression and aggressiveness. These results suggest a contribution of synapses between GB cells to disease progression, named as intratumoral synapses.

Aberrant Expression of Cardiac Troponin-T in Lung Cancer Tissues in Association With Pathological Severity

Background

Cardiac troponin-T (TNNT2) is exclusively present in cardiac muscle. Measurement of TNNT2 is used for diagnosing acute coronary syndrome. However, its expression may not be limited in myocardium. This study aimed at evaluating the expression of TNNT2 in neoplastic tissues.

Methods and Results

We used paraffin-embedded blocks of 68 patients with lung cancer (age, 68 ± 11 years old; early-stage, 33; advance-stage, 35) at Miyazaki University Hospital, Japan between January 1, 2017, and March 31, 2019. We stained the slide sections with primary monoclonal antibody against TNNT2 protein, and assessed the frequency of positive staining, and its association with pathological severity. In addition, we examined whether TNNT2 gene is detected in lung cancer tissues of four patients using reverse transcription-polymerase chain reaction. Immunoreactivity for TNNT2 protein was present in the cytoplasm and nucleus of lung cancer cells. The frequency was 37% (25 of 68) in all patients and was irrespective of histologic type (six of 13, squamous cell carcinoma; 18 of 50, adenocarcinoma; 0 of 4, neuroendocrine cell carcinoma; 1 of 1, large cell carcinoma). The prevalence increased with pathological staging [9% (3 of 33) at early-stage (Stage 0–I); 63% (22 of 35) at advance-stage (Stage II–IV and recurrence)]. In addition, frequency of positive staining for TNNT2 increased with pleural (χ² = 5.877, P = 0.015) and vascular (χ² = 2.449, P = 0.118) invasions but decreased with lymphatic invasion (χ² = 3.288, P = 0.070) in specimens performed surgical resection. Furthermore, TNNT2 mRNA was detected in the resected squamous cell carcinoma and adenocarcinoma tissues.

Conclusions

Our data suggest the aberrant expression of TNNT2 in lung cancer and its prevalence increases with pathological severity.

A role for Flower and cell death in controlling morphogen gradient scaling

During development, morphogen gradients encode positional information to pattern morphological structures during organogenesis¹. Some gradients, like that of Dpp in the fly wing, remain proportional to the size of growing organs-that is, they scale. Gradient scaling keeps morphological patterns proportioned in organs of different sizes^2,3. Here we show a mechanism of scaling that ensures that, when the gradient is smaller than the organ, cell death trims the developing tissue to match the size of the gradient. Scaling is controlled by molecular associations between Dally and Pentagone, known factors involved in scaling, and a key factor that mediates cell death, Flower^4-6. We show that Flower activity in gradient expansion is not dominated by cell death, but by the activity of Dally/Pentagone on scaling. Here we show a potential connection between scaling and cell death that may uncover a molecular toolbox hijacked by tumours.

Circadian Gene cry Controls Tumorigenesis through Modulation of Myc Accumulation in Glioblastoma Cells

Glioblastoma (GB) is the most frequent malignant brain tumor among adults and currently there is no effective treatment. This aggressive tumor grows fast and spreads through the brain causing death in 15 months. GB cells display a high mutation rate and generate a heterogeneous population of tumoral cells that are genetically distinct. Thus, the contribution of genes and signaling pathways relevant for GB progression is of great relevance. We used a Drosophila model of GB that reproduces the features of human GB and describe the upregulation of the circadian gene cry in GB patients and in a Drosophila GB model. We studied the contribution of cry to the expansion of GB cells and the neurodegeneration and premature death caused by GB, and we determined that cry is required for GB progression. Moreover, we determined that the PI3K pathway regulates cry expression in GB cells, and in turn, cry is necessary and sufficient to promote Myc accumulation in GB. These results contribute to understanding the mechanisms underlying GB malignancy and lethality, and describe a novel role of Cry in GB cells.

The haplolethality paradox of the wupA gene in Drosophila

Haplolethals (HL) are regions of diploid genomes that in one dose are fatal for the organism. Their biological meaning is obscure because heterozygous loss-of-function mutations result in dominant lethality (DL) and, consequently, should be under strong negative selection. We report an in depth study of the HL associated to the gene wings up A (wupA). It encodes 13 transcripts (A-M) that yield 11 protein isoforms (A-K) of Troponin I (TnI). They are functionally diverse in their control of muscle contraction, cell polarity and cell proliferation. Isoform K transfers to the nucleus where it increases transcription of the cell proliferation related genes CDK2, CDK4, Rap and Rab5. The nuclear translocation of isoform K is prevented by the co-expression of A or B isoforms, which illustrates isoform interactions. The corresponding DL mutations are, either DNA rearrangements clustered towards the gene 3’ end, thus affecting the genomic organization of all transcripts, or CRISPR-induced mutations in one of the two ATG sites which eliminate a subset of wupA products. The joint elimination of isoforms C, F, G and H, however, do not cause DL phenotypes. Genetically driven expression of single isoforms rescue neither DL nor any of the mutants known in the gene, suggesting that normal function requires properly regulated expression of specific combinations, rather than single, TnI isoforms. We conclude that the wupA associated HL results from the combined haploinsufficiency of a large set of TnI isoforms. The qualitative and quantitative normal expression of which, requires the chromosomal integrity of the wupA genomic region. Since all fly TnI isoforms are encoded in the same gene, its HL condition becomes unavoidable. These wupA features are comparable to those of dpp, the only other HL studied to some extent, and reveal a scenario of strict dosage dependence with implications for gene expression regulation and splitting.

Most species contain two copies of their genetic endowment, each received from each progenitor. If one of the duplicated genes is non-functional, the remaining copy may supply enough product as to cover the requirements for normal function or, alternatively, may reflect the insufficiency through a visible phenotype. In rare occasions, however, having one copy is so deleterious that causes lethality. These so called “haplolethal regions”, exist across species and represent an evolutionary paradox since they should have been subject to intense negative selection. The inherent difficulties to study haplolethals have precluded their study so far. Here, we analyzed the case of one of the five haplolethal regions of Drosophila, the one associated to the Troponin I encoding gene wupA, by measuring the transcriptional effects of mutations and chromosomal rearrangements affecting this gene. The data show that this haplolethality results from the combined insufficiency of a large number of Troponin I isoforms, which are functionally specialized, show interference and require the integrity of the native chromatin structure for their quantitatively regulated expression. These features unveil novel aspects of gene expression and, possibly, on evolutionary gene splitting. Also, haplolethals underscore the biological significance of protein dosage, in particular for functionally related products.

Molecular alterations in oral cancer using high-throughput proteomic analysis of formalin-fixed paraffin-embedded tissue

Loss of cell differentiation is a hallmark for the progression of oral squamous cell carcinoma (OSCC). Archival Formalin-Fixed Paraffin-Embedded (FFPE) tissues constitute a valuable resource for studying the differentiation of OSCC and can offer valuable insights into the process of tumor progression. In the current study, we performed LC-MS/MS-based quantitative proteomics of FFPE specimens from pathologically-confirmed well-differentiated, moderately-differentiated, and poorly-differentiated OSCC cases. The data were analyzed in four technical replicates, resulting in the identification of 2376 proteins. Of these, 141 and 109 were differentially expressed in moderately-differentiated and poorly differentiated OSCC cases, respectively, compared to well-differentiated OSCC. The data revealed significant metabolic reprogramming with respect to lipid metabolism and glycolysis with proteins belonging to both these processes downregulated in moderately-differentiated OSCC when compared to well-differentiated OSCC. Signaling pathway analysis indicated the alteration of extracellular matrix organization, muscle contraction, and glucose metabolism pathways across tumor grades. The extracellular matrix organization pathway was upregulated in moderately-differentiated OSCC and downregulated in poorly differentiated OSCC, compared to well-differentiated OSCC. PADI4, an epigenetic enzyme transcriptional regulator, and its transcriptional target HIST1H1B were both found to be upregulated in moderately differentiated and poorly differentiated OSCC, indicating epigenetic events underlying tumor differentiation. In conclusion, the findings support the advantage of using high-resolution mass spectrometry-based FFPE archival blocks for clinical and translational research. The candidate signaling pathways identified in the study could be used to develop potential therapeutic targets for OSCC.

TNNC1 knockout reverses metastatic potential of ovarian cancer cells by inactivating epithelial-mesenchymal transition and suppressing F-actin polymerization

Troponin C type 1 (TNNC1) is commonly overexpressed in ovarian cancer. However, the biological implications of TNNC1 overexpression on ovarian cancer malignization and its related mechanism remain unknown. To elucidate these implications, we knocked out the TNNC1 gene in TNNC1-overexpressing SKOV-3-13 ovarian cancer cells using CRISPR/Cas-9 technology and observed the changes in metastatic phenotypes and related molecular pathways. TNNC1-knockout (KO) cells showed significantly reduced proliferation and colony formation when compared with TNNC1 wild-type cells (P < 0.01). In TNNC1-KO cells, wound healing, migration, and invasive phenotypes decreased. Upon observation of upstream regulators of epithelial-mesenchymal transition (EMT), levels of phosphorylated AKT (Ser-473 and Thr-308) and GSK-3β (inactive form) were found to be decreased in TNNC1-KO cells. Accordingly, SNAIL and SLUG expression decreased and were almost completely localized in the cytoplasm following TNNC1 silencing. Regarding downstream EMT markers, N-cadherin and vimentin expression decreased, but E-cadherin expression increased. Related matrix metalloproteinase and chemokine expression generally decreased. TNNC1 deficiency also suppressed F-actin polymerization. In conclusion, TNNC1 overexpression contributes to the metastatic behavior of ovarian cancer by perturbation of EMT and actin microfilaments. Our results provide a better understanding of the detailed molecular mechanism of ovarian cancer metastasis associated with TNNC1 overexpression.

Emerging mechanisms of cell competition

The growth and survival of cells within tissues can be affected by 'cell competition' between different cell clones. This phenomenon was initially recognized between wild-type cells and cells with mutations in ribosomal protein (Rp) genes in Drosophila melanogaster. However, competition also affects D. melanogaster cells with mutations in epithelial polarity genes, and wild-type cells exposed to 'super-competitor' cells with mutation in the Salvador-Warts-Hippo tumour suppressor pathway or expressing elevated levels of Myc. More recently, cell competition and super-competition were recognized in mammalian development, organ homeostasis and cancer. Genetic and cell biological studies have revealed that mechanisms underlying cell competition include the molecular recognition of 'different' cells, signalling imbalances between distinct cell populations and the mechanical consequences of differential growth rates; these mechanisms may also involve innate immune proteins, p53 and changes in translation.

Characterization of TNNC1 as a Novel Tumor Suppressor of Lung Adenocarcinoma

In this study, we describe a novel function of TNNC1 (Troponin C1, Slow Skeletal and Cardiac Type), a component of actin-bound troponin, as a tumor suppressor of lung adenocarcinoma (LUAD). First, the expression of TNNC1 was strongly down-regulated in cancer tissues compared to matched normal lung tissues, and down-regulation of TNNC1 was shown to be strongly correlated with increased mortality among LUAD patients. Interestingly, TNNC1 expression was enhanced by suppression of KRAS, and ectopic expression of TNNC1 in turn inhibited KRASG12D-mediated anchorage independent growth of NIH3T3 cells. Consistently, activation of KRAS pathway in LUAD patients was shown to be strongly correlated with down-regulation of TNNC1. In addition, ectopic expression of TNNC1 inhibited colony formation of multiple LUAD cell lines and induced DNA damage, cell cycle arrest and ultimately apoptosis. We further examined potential correlations between expression levels of TNNC1 and various clinical parameters and found that low-level expression is significantly associated with invasiveness of the tumor. Indeed, RNA interference-mediated down-regulation of TNNC1 led to significant enhancement of invasiveness in vitro. Collectively, our data indicate that TNNC1 has a novel function as a tumor suppressor and is targeted for down-regulation by KRAS pathway during the carcinogenesis of LUAD.

Switching of cardiac troponin I between nuclear and cytoplasmic localization during muscle differentiation

The nuclear accumulation of proteins may depend on the presence of short targeting sequences, which are known as nuclear localization signals (NLSs). Here, we found that NLSs are predicted in some cytosolic proteins and examined the hypothesis that these NLSs may be functional under certain conditions. As a model, human cardiac troponin I (hcTnI) was used. After expression in cultured non-muscle or undifferentiated muscle cells, hcTnI accumulated inside nuclei. Several NLSs were predicted and confirmed by site-directed mutagenesis in hcTnI. Nuclear import occurred via the classical karyopherin-α/β nuclear import pathway. However, hcTnI expressed in cultured myoblasts redistributed from the nucleus to the cytoplasm, where it was integrated into forming myofibrils after the induction of muscle differentiation. It appears that the dynamic retention of proteins inside cytoplasmic structures can lead to switching between nuclear and cytoplasmic localization.

An 8‑gene signature predicts the prognosis of cervical cancer following radiotherapy

Gene expression and DNA methylation levels affect the outcomes of patients with cancer. The present study aimed to establish a multigene risk model for predicting the outcomes of patients with cervical cancer (CerC) treated with or without radiotherapy. RNA sequencing training data with matched DNA methylation profiles were downloaded from The Cancer Genome Atlas database. Patients were divided into radiotherapy and non‑radiotherapy groups according to the treatment strategy. Differently expressed and methylated genes between the two groups were identified, and 8 prognostic genes were identified using Cox regression analysis. The optimized risk model based on the 8‑gene signature was defined using the Cox's proportional hazards model. Kaplan‑Meier survival analysis indicated that patients with higher risk scores exhibited poorer survival compared with patients with lower risk scores (log‑rank test, P=3.22x10‑7). Validation using the GSE44001 gene set demonstrated that patients in the high‑risk group exhibited a shorter survival time comprared with the low‑risk group (log‑rank test, P=3.01x10‑3). The area under the receiver operating characteristic curve values for the training and validation sets were 0.951 and 0.929, respectively. Cox regression analyses indicated that recurrence and risk status were risk factors for poor outcomes in patients with CerC treated with or without radiotherapy. The present study defined that the 8‑gene signature was an independent risk factor for the prognosis of patients with CerC. The 8‑gene prognostic model had predictive power for CerC prognosis.

Troponin-I mediates the localization of selected apico-basal cell polarity signaling proteins

Beyond its role in muscle contraction, Drosophila Troponin I (TnI; also known as Wings up A) is expressed in epithelial cells where it controls proliferation. TnI traffics between nucleus and cytoplasm through a sumoylation-dependent mechanism. We address here the role of TnI in the cytoplasm. TnI accumulates apically in epidermal cells and neuroblasts. TnI co-immunoprecipitates with Bazooka (also known as Par3) and Discs large (Dlg1, hereafter Dlg), two apico-basal polarity components. TnI depletion causes Baz and Dlg mislocalization; by contrast, the basolateral localization of Scribbled is not altered. In neuroblasts, TnI contributes to the polar localization of Miranda, while non-polar Dlg localization is not affected. Vertebrate phosphoinositide 3-kinase (PI3K) contributes to the apico-basal polarity of epithelia, but we find that Drosophila PI3K depletion alters neither the apical localization of TnI or Bazooka, nor the basal localization of Dlg. Nevertheless, overexpressing PI3K prevents the defects seen upon TnI depletion. TnI loss-of-function disrupts cytoskeletal β-Catenin, E-Cadherin and γ-Tubulin, and causes an increase in DNA damage, as revealed by analyzing γH2Av. We have previously shown that TnI depletion leads to apoptosis that can be suppressed by upregulating Sparc or downregulating Dronc. However, TnI-depleted cells expressing Sparc or downregulating Dronc, as well as those expressing p35 (also known as Cdk5α), that do not undergo apoptosis, still show DNA damage. This indicates that DNA damage is mechanistically independent of apoptosis induction. Thus, TnI binds certain apico-basal polarity signaling proteins in a cell type-dependent context, and this unveils a previously unsuspected diversity of mechanisms to allocate cell polarity factors.

Drosophila Models of Cell Polarity and Cell Competition in Tumourigenesis

Cell competition is an important surveillance mechanism that measures relative fitness between cells in a tissue during development, homeostasis, and disease. Specifically, cells that are "less fit" (losers) are actively eliminated by relatively "more fit" (winners) neighbours, despite the less fit cells otherwise being able to survive in a genetically uniform tissue. Originally described in the epithelial tissues of Drosophila larval imaginal discs, cell competition has since been shown to occur in other epithelial and non-epithelial Drosophila tissues, as well as in mammalian model systems. Many genes and signalling pathways have been identified as playing conserved roles in the mechanisms of cell competition. Among them are genes required for the establishment and maintenance of apico-basal cell polarity: the Crumbs/Stardust/Patj (Crb/Sdt/Patj), Bazooka/Par-6/atypical Protein Kinase C (Baz/Par-6/aPKC), and Scribbled/Discs large 1/Lethal (2) giant larvae (Scrib/Dlg1/L(2)gl) modules. In this chapter, we describe the concepts and mechanisms of cell competition, with emphasis on the relationship between cell polarity proteins and cell competition, particularly the Scrib/Dlg1/L(2)gl module, since this is the best described module in this emerging field.

Systemic signalling and local effectors in developmental stability, body symmetry, and size

Symmetric growth and the origins of fluctuating asymmetry are unresolved phenomena of biology. Small, and sometimes noticeable, deviations from perfect bilateral symmetry reflect the vulnerability of development to perturbations. The degree of asymmetry is related to the magnitude of the perturbations and the ability of an individual to cope with them. As the left and right sides of an individual were presumed to be genetically identical, deviations of symmetry were traditionally attributed to non-genetic effects such as environmental and developmental noise. In this review, we draw attention to other possible sources of variability, especially to somatic mutations and transposons. Mutations are a major source of phenotypic variability and recent genomic data have highlighted somatic mutations as ubiquitous, even in phenotypically normal individuals. We discuss the importance of factors that are responsible for buffering and stabilizing the genome and for maintaining size robustness and quality through elimination of less-fit or damaged cells. However, the important question that arises from these studies is whether this self-correcting capacity and intrinsic organ size controls are sufficient to explain how symmetric structures can reach an identical size and shape. Indeed, recent discoveries in the fruit fly have uncovered a conserved hormone of the insulin/IGF/relaxin family, Dilp8, that is responsible for stabilizing body size and symmetry in the face of growth perturbations. Dilp8 alarm signals periphery growth status to the brain, where it acts on its receptor Lgr3. Loss of Dilp8-Lgr3 signaling renders flies incapable of detecting growth perturbations and thus maintaining a stable size and symmetry. These findings help to understand how size and symmetry of somatic tissues remain undeterred in noisy environments, after injury or illnesses, and in the presence of accumulated somatic mutations.

Troponin T3 associates with DNA consensus sequence that overlaps with p53 binding motifs

We recently reported that in addition to its classical cytoplasmic location, the fast skeletal muscle Troponin T3 (TnT3) shuttles to the nucleus, where it appears to perform nonclassical transcription regulatory functions. Importantly, changes in the composition of the nucleus-localized pool of TnT3 and its fragments contribute to age-dependent muscle damage and wasting. Here, using ChIP-Seq, we demonstrate that TnT3 associates with DNA consensus sequences including the TGCCT motif, which is required for p53 binding to the promoter area of p53-related genes. Gene set enrichment analysis further demonstrated that the p53 pathway was the most significantly enriched pathway among genes annotated to the TnT3 ChIP-Seq peaks. We further demonstrated a strong correlation (r = 0.78, P = 1 × 10^-4) between the expression levels of TNNT3 and TP53-inducible ribonucleotide reductase regulatory subunit M2B (RRM2B) in skeletal muscle tissue of 21 lean non-diabetic human subjects and a significant (P < 0.05) reduction in the levels of both gene transcripts in the third age-tertile group [42.3-70 years of age (yoa)] as compared to the second age-tertile (31.3-42.3 yoa). Of note, both TNNT3 and RRM2B expression levels negatively associated with total body fat mass (each with r = 0.49, P < 0.05), whereas RRM2B positively correlated with pancreatic β cell function (r_RRM2B~HOMA-B = 0.47, P = 0.047). This work suggests that reduced TNNT3 gene expression is another mechanism leading to reduced TnT3 and excitation-contraction coupling with aging. Consequently, TnT3 appears to contribute to age-related sarcopenia and possibly other age-related deficiencies such as muscle insulin resistance and β cell dysfunction by interacting with TnT3-binding sequences in the promoter area of p53-related genes, among others, and consequently modulating the transcriptional regulation of these target genes.

Modelling Cooperative Tumorigenesis in Drosophila

The development of human metastatic cancer is a multistep process, involving the acquisition of several genetic mutations, tumour heterogeneity, and interactions with the surrounding microenvironment. Due to the complexity of cancer development in mammals, simpler model organisms, such as the vinegar fly, Drosophila melanogaster, are being utilized to provide novel insights into the molecular mechanisms involved. In this review, we highlight recent advances in modelling tumorigenesis using the Drosophila model, focusing on the cooperation of oncogenes or tumour suppressors, and the interaction of mutant cells with the surrounding tissue in epithelial tumour initiation and progression.

Troponin through the looking-glass: emerging roles beyond regulation of striated muscle contraction

Troponin is a heterotrimeric Ca²⁺-binding protein that has a well-established role in regulating striated muscle contraction. However, mounting evidence points to novel cellular functions of troponin, with profound implications in cancer, cardiomyopathy pathogenesis and skeletal muscle aging. Here, we highlight the non-canonical roles and aberrant expression patterns of troponin beyond the sarcomeric milieu. Utilizing bioinformatics tools and online databases, we also provide pathway, subcellular localization, and protein-protein/DNA interaction analyses that support a role for troponin in multiple subcellular compartments. This emerging knowledge challenges the conventional view of troponin as a sarcomere-specific protein exclusively involved in muscle contraction and may transform the way we think about sarcomeric proteins, particularly in the context of human disease and aging.

Mechanisms of cell competition emerging from Drosophila studies

Cell competition was described in Drosophila as the loss from mosaic tissues of otherwise viable cells heterozygous for Ribosomal protein mutations ('Minutes'). Cell competition has now been described to occur between multiple other genotypes, such as cells differing in myc expression levels, or mutated for neoplastic tumor suppressors. Recent studies implicate innate immunity components, and possibly mechanical stress, compression and cell intercalation as a consequence of differential growth rates in competitive cell death. Competition to eliminate pre-neoplastic tumors makes use of signals and receptors also used in patterning the nervous system including Slit/Robo2 and Sas/PTP10D to recognize and extrude clones of mutant cells, at least where local epithelial cyto-architecture is favorable. Cell competition facilitates expansion of Drosophila tumors through host tissue, and in normal development may promote developmental robustness and longevity by selecting for optimal progenitor cells.