Cancer and meiotic gene expression: Two sides of the same coin?

Repeated ionizing radiation exposure induces TRIP13 expression, conferring radioresistance in lung cancer cells

Radiation therapy is a common treatment modality for lung cancer, and resistance to radiation can significantly affect treatment outcomes. We recently described that lung cancer cells that express more germ cell cancer genes (GC genes, genes that are usually restricted to the germ line) can repair DNA double-strand breaks more rapidly, show higher rates of proliferation and are more resistant to ionizing radiation than cells that express fewer GC genes. The gene encoding TRIP13 appeared to play a large role in this malignant phenotype. However, the molecular regulatory mechanism of TRIP13 in radiation resistance remained largely unknown. Here, we show that TRIP13 is a key contributor to non-small cell lung cancer (NSCLC) treatment resistance, particularly in patients following radiation treatment, for whom levels of TRIP13 expression are correlated with a poor prognosis. Repeated irradiation of led to an increase of basal TRIP13 levels and radioresistance. This effect of radioresistance could be enhanced or abrogated by overexpressing or knocking out TRIP13. Elevated TRIP13 is also correlated with enhanced repair of radiation-induced DNA damage. We further showed the proteins NBS1 and RAD51 (homologous recombination. HR) and XRCC5 (non-homologous end-joining, NHEJ) to act downstream of TRIP13, although inhibition of TRIP13 mostly reduced the HR associated proteins in response to induced resistance to irradiation. This study elucidates a novel mechanism of treatment resistance in NSCLC cells, in which TRIP13 promotes HR mediated DNA repair and resistance to ionizing radiation.

Transcriptomic changes and gene fusions during the progression from Barrett's esophagus to esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has surged by 600% in recent decades, with a dismal 5-year survival rate of just 15%. Barrett's esophagus (BE), affecting about 2% of the population, raises the risk of EAC by 40-fold. Despite this, the transcriptomic changes during the BE to EAC progression remain unclear. Our study addresses this gap through comprehensive transcriptomic profiling to identify key mRNA signatures and genomic alterations, such as gene fusions. We performed RNA-sequencing on BE and EAC tissues from 8 individuals, followed by differential gene expression, pathway and network analysis, and gene fusion prediction. We identified mRNA changes during the BE-to-EAC transition and validated our results with single-cell RNA-seq datasets. We observed upregulation of keratin family members in EAC and confirmed increased levels of keratin 14 (KRT14) using immunofluorescence. More differentiated BE marker genes are downregulated during progression to EAC, suggesting undifferentiated BE subpopulations contribute to EAC. We also identified several gene fusions absent in paired BE and normal esophagus but present in EAC. Our findings are critical for the BE-to-EAC transition and have the potential to promote early diagnosis, prevention, and improved treatment strategies for EAC.

PPP2R1A silencing suppresses LUAD progression by sensitizing cells to nelfinavir-induced apoptosis and pyroptosis

Lung adenocarcinoma is a major public health problem with the low 5-year survival rate (15%) among cancers. Aberrant alterations of meiotic genes, which have gained increased attention recently, might contribute to elevated tumor risks. However, systematic and comprehensive studies based on the relationship between meiotic genes and LUAD recurrence and treatment response are still lacking. In this manuscript, we first confirmed that the meiosis related prognostic model (MRPM) was strongly related to LUAD progression via LASSO-Cox regression analyses. Furthermore, we identified the role of PPP2R1A in LUAD, which showed more contributions to LUAD process compared with other meiotic genes in our prognostic model. Additionally, repression of PPP2R1A enhances cellular susceptibility to nelfinavir-induced apoptosis and pyroptosis. Collectively, our findings indicated that meiosis-related genes might be therapeutic targets in LUAD and provided crucial guidelines for LUAD clinical intervention.

Germline specific genes increase DNA double-strand break repair and radioresistance in lung adenocarcinoma cells

In principle, germline cells possess the capability to transmit a nearly unaltered set of genetic material to infinite future generations, whereas somatic cells are limited by strict growth constraints necessary to assure an organism's physical structure and eventual mortality. As the potential to replicate indefinitely is a key feature of cancer, we hypothesized that the activation of a "germline program" in somatic cells can contribute to oncogenesis. Our group recently described over one thousand germline specific genes that can be ectopically expressed in cancer, yet how germline specific processes contribute to the malignant properties of cancer is poorly understood. We here show that the expression of germ cell/cancer (GC) genes correlates with malignancy in lung adenocarcinoma (LUAD). We found that LUAD cells expressing more GC genes can repair DNA double strand breaks more rapidly, show higher rates of proliferation and are more resistant to ionizing radiation, compared to LUAD cells that express fewer GC genes. In particular, we identified the HORMA domain protein regulator TRIP13 to be predominantly responsible for this malignant phenotype, and that TRIP13 inhibition or expression levels affect the response to ionizing radiation and subsequent DNA repair. Our results demonstrate that GC genes are viable targets in oncology, as they induce increased radiation resistance and increased propagation in cancer cells. Because their expression is normally restricted to germline cells, we anticipate that GC gene directed therapeutic options will effectively target cancer, with limited side effects besides (temporary) infertility.

SEPT9, H4C6, and RASSF1A methylation in nasopharyngeal swabs: A reflection of potential minimally invasive biomarkers for early screening of nasopharyngeal cancer

The potential value of epigenetic DNA methylation in early cancer screening has been demonstrated. Therefore, in this study, we performed QMS-PCR and quantitative reverse transcription PCR on the genes RASSF1A, H4C6, SEPT9, GSTP1, PAX1, SHOX2, and SOX2, which are common in epithelial cancers. We found hypermethylation in RASSF1A, H4C6 and SEPT9. The mRNA expressions of RASSF1A, H4C6 and SEPT9 in tumor group were significantly different from those in the inflammatory group and healthy group (P < .05). Receiver operating characteristic (ROC) analysis showed that the area under the curve (AUC) of RASSF1A, H4C6 and SEPT9 genes were 0.831, 0.856 and 0.767, respectively. The areas under the AUC curve of SEPT9 + H4C6, SEPT9 + RASSF1A and H4C6 + RASSF1A are 0.946, 0.912 and 0.851, respectively. The diagnostic ability of dual gene combination is better than that of single gene combination, among which SEPT9 and H4C6 combination has the best diagnostic effect. In conclusion, our findings suggest that H4C6, RASSF1A, and SEPT9 methylation occur more frequently in nasopharyngeal carcinoma, and their detection in nasopharyngeal swabs may be a minimally invasive tool for diagnosis of nasopharyngeal carcinoma.

Aberrant activation of five embryonic stem cell-specific genes robustly predicts a high risk of relapse in breast cancers

BACKGROUND

In breast cancer, as in all cancers, genetic and epigenetic deregulations can result in out-of-context expressions of a set of normally silent tissue-specific genes. The activation of some of these genes in various cancers empowers tumours cells with new properties and drives enhanced proliferation and metastatic activity, leading to a poor survival prognosis.

RESULTS

In this work, we undertook an unprecedented systematic and unbiased analysis of out-of-context activations of a specific set of tissue-specific genes from testis, placenta and embryonic stem cells, not expressed in normal breast tissue as a source of novel prognostic biomarkers. To this end, we combined a strict machine learning framework of transcriptomic data analysis, and successfully created a new robust tool, validated in several independent datasets, which is able to identify patients with a high risk of relapse. This unbiased approach allowed us to identify a panel of five biomarkers, DNMT3B, EXO1, MCM10, CENPF and CENPE, that are robustly and significantly associated with disease-free survival prognosis in breast cancer. Based on these findings, we created a new Gene Expression Classifier (GEC) that stratifies patients. Additionally, thanks to the identified GEC, we were able to paint the specific molecular portraits of the particularly aggressive tumours, which show characteristics of male germ cells, with a particular metabolic gene signature, associated with an enrichment in pro-metastatic and pro-proliferation gene expression.

CONCLUSIONS

The GEC classifier is able to reliably identify patients with a high risk of relapse at early stages of the disease. We especially recommend to use the GEC tool for patients with the luminal-A molecular subtype of breast cancer, generally considered of a favourable disease-free survival prognosis, to detect the fraction of patients undergoing a high risk of relapse.

How germline genes promote malignancy in cancer cells

Cancers often express hundreds of genes otherwise specific to germ cells, the germline/cancer (GC) genes. Here, we present and discuss the hypothesis that activation of a "germline program" promotes cancer cell malignancy. We do so by proposing four hallmark processes of the germline: meiosis, epigenetic plasticity, migration, and metabolic plasticity. Together, these hallmarks enable replicative immortality of germ cells as well as cancer cells. Especially meiotic genes are frequently expressed in cancer, implying that genes unique to meiosis may play a role in oncogenesis. Because GC genes are not expressed in healthy somatic tissues, they form an appealing source of specific treatment targets with limited side effects besides infertility. Although it is still unclear why germ cell specific genes are so abundantly expressed in cancer, from our hypothesis it follows that the germline's reproductive program is intrinsic to cancer development.

Cyclins and CDKs in the regulation of meiosis-specific events

How eukaryotic cells control their duplication is a fascinating example of how a biological system self-organizes specific activities to temporally order cellular events. During cell cycle progression, the cellular level of CDK (Cyclin-Dependent Kinase) activity temporally orders the different cell cycle phases, ensuring that DNA replication occurs prior to segregation into two daughter cells. CDK activity requires the binding of a regulatory subunit (cyclin) to the core kinase, and both CDKs and cyclins are well conserved throughout evolution from yeast to humans. As key regulators, they coordinate cell cycle progression with metabolism, DNA damage, and cell differentiation. In meiosis, the special cell division that ensures the transmission of genetic information from one generation to the next, cyclins and CDKs have acquired novel functions to coordinate meiosis-specific events such as chromosome architecture, recombination, and synapsis. Interestingly, meiosis-specific cyclins and CDKs are common in evolution, some cyclins seem to have evolved to acquire CDK-independent functions, and even some CDKs associate with a non-cyclin partner. We will review the functions of these key regulators in meiosis where variation has specially flourished.