5. projekta publikācijas 2011drukāt
Huna A, Salmina K, Jascenko E, Duburs G, Inashkina I, Erenpreisa J. Self-Renewal Signalling in Presenescent Tetraploid IMR90 Cells. J Aging Res. 2011;2011:103253 . Epub 2011 May 11.
Endopolyploidy and genomic instability are shared features of both stress-induced cellular senescence and malignant growth. Here, we examined these facets in the widely used normal human fibroblast model of senescence, IMR90. At the presenescence stage, a small (2-7%) proportion of cells overcome the 4n-G1 checkpoint, simultaneously inducing self-renewal (NANOG-positivity), the DNA damage response (DDR; γ-H2AX-positive foci), and senescence (p16inka4a- and p21CIP1-positivity) signalling, some cells reach octoploid DNA content and divide. All of these markers initially appear and partially colocalise in the perinucleolar compartment. Further, with development of senescence and accumulation of p16inka4a and p21CIP1, NANOG is downregulated in most cells. The cells increasingly arrest in the 4n-G1 fraction, completely halt divisions and ultimately degenerate. A positive link between DDR, self-renewal, and senescence signalling is initiated in the cells overcoming the tetraploidy barrier, indicating that cellular and molecular context of induced tetraploidy during this period of presenescence is favourable for carcinogenesis.
Erenpreisa J., Cragg MS, Anisimov AP, Illidge TM.Tumor cell embryonality and the ploidy number 32n: is it a developmental checkpoint? Cell Cycle. 2011 Jun 1;10(11):1873-4. Epub 2011 Jun 1.
Erenpreisa J., Salmina K, Huna A, Kosmacek EA, Cragg MS, Ianzini F, Anisimov AP. Polyploid tumour cells elicit para-diploid progeny through de-polyploidising divisions and regulated autophagic degradation. Cell Biol Int. 2011, 35:687-95.
'Neosis' describes the process whereby p53 function-deficient tumour cells undergo self-renewal after genotoxic damage apparently via senescing ETCs (endopolyploid tumour cells). We previously reported that autophagic digestion and extrusion of DNA occurs in ETC and subsequently revealed that self-renewal transcription factors are also activated under these conditions. Here, we further studied this phenomenon in a range of cell lines after genotoxic damage induced by gamma irradiation, ETO (etoposide) or PXT (paclitaxel) treatment. These experiments revealed that chromatin degradation by autophagy was compatible with continuing mitotic activity in ETC. While the actively polyploidizing primary ETC produced early after genotoxic insult activated self-renewal factors throughout the polygenome, the secondary ETC restored after failed multipolar mitosis underwent subnuclei differentiation. As such, only a subset of subnuclei continued to express OCT4 and NANOG, while those lacking these factors stopped DNA replication and underwent degradation and elimination through autophagy. The surviving subnuclei sequestered nascent cytoplasm to form subcells, while being retained within the confines of the old ETC. Finally, the preformed paradiploid subcells became released from their linking chromosome bridges through autophagy and subsequently began cell divisions. These data show that 'neotic' ETC resulting from genotoxically damaged p53 function-deficient tumour cells develop through a heteronuclear system differentiating the polyploid genome into rejuvenated 'viable' subcells (which provide mitotically propagating paradiploid descendents) and subnuclei, which become degraded and eliminated by autophagy. The whole process reduces aneuploidy in descendants of ETC.
Kristine Salmina, Eriks Jankevics, Anda Huna, Dmitry Perminov, Ilze Radovica,Tetyana Klymenko, Andrey Ivanov, Elina Jascenko, Harry Scherthan, Mark Cragg, Jekaterina Erenpreisa (2010) Up-regulation of the embryonic self-renewal network through reversible polyploidy in irradiated p53-mutant tumour cells. Exp Cell Res 316:2099- 2112.
We have previously documented that transient polyploidy is a potential cell survival strategy underlying the clonogenic re-growth of tumour cells after genotoxic treatment. In an attempt to better define this mechanism, we recently documented the key role of meiotic genes in regulating the DNA repair and return of the endopolyploid tumour cells (ETC) to diploidy through reduction divisions after irradiation. Here, we studied the role of the pluripotency and self-renewal stem cell genes NANOG, OCT4 and SOX2 in this polyploidy-dependent survival mechanism. In irradiation resistant p53-mutated lymphoma cell-lines (Namalwa and WI-L2-NS) but not sensitive p53 wildtype counterparts (TK6), low background expression of OCT4 and NANOG was up-regulated by ionising radiation with protein accumulation evident in ETC as detected by OCT4/DNA flow cytometry and immunofluorescence (IF). IF analysis also showed that the ETC generate PML bodies that appear to concentrate OCT4, NANOG and SOX2 proteins, which extend into complex nuclear networks. These polyploid tumour cells resist apoptosis, overcome cellular senescence and undergo bi- and multi-polar divisions transmitting the up-regulated OCT4, NANOG and SOX2 selfrenewal cassette to their descendents. Altogether, our observations indicate that irradiation induced ETC up-regulate key components of germ-line cells, which potentially facilitate survival and propagation of the tumour cell population.
Erenpreisa Je and Cragg MS (2010) MOS, aneuploidy and the ploidy cycle of cancer cells. Oncogene 29:5447-5451.
After DNA or spindle damage, p53-defective tumor cells undergo a complex cycle of reversible polyploidy. How this process occurs and more importantly, why, has recently become the focus of several research groups, prompting this review in which we discuss two related phenomena that accompany the reversible polyploidy of tumor cells: the induction of meiosis genes such as MOS and the decrease in genomic instability observed during the reversion from polyploidy to para-diploidy. The reversible polyploidy likely provides the means through which the balance between increased chromosome instability (CIN), driving genetic variation and decreased CIN, necessary for perpetuating these malignant clones, is maintained. These concepts are integrated with recent findings that many meiotic and self-renewal genes become activated during reversible polyploidy and lead us to the hypothesis that tumor cell immortality may be achieved through germline-like transmission.
K. Silina, P. Zayakin, Z. Kalnina, L. Ivanova, I. Meistere, A. Abols, A. Stengrevics, M. Leja, E.M.I. Suso, G. Gaudernack, T. Wex, D. Schadendorf, A. Line. Molecular analysis of serologically identified tumour antigens reveals novel cancer-testis antigens as potential targets for cancer immunotherapy (submitted to: Cancer Immunology and Immunotherapy; currently under revision)
Previously using phage display-based SEREX approach we identified 1328 antigens recognised by autoantibodies from melanoma, breast, prostate and gastric cancer patients. 198 antigens were translated in their natural open reading frames (ORF) including well-known cancer-testis (CT) and known autoantigens as well as 79 previously uncharacterized antigens, 21 antigens were encoded by uncharacterized genes or novel splice variants termed as undefined ORF antigens, while the remaining clones were translated as unnatural ORF peptides. The current study was aimed to find out whether any of the novel natural and undefined ORF antigens could serve as targets for cancer immunotherapy. First, their autoantibody frequency was assessed in sera from 376 cancer patients and 153 healthy individuals using phage-displayed antigen microarrays. Next, antigens with cancer-related humoral response were prioritized according their EST tissue distribution, functional significance and structural motifs and 28 top-ranked antigens were subjected to mRNA expression analysis in 14 various normal tissues and melanoma, breast, and gastric cancer-normal tissue pairs. Normal tissue analysis revealed ten antigens with testis-associated expression pattern. Two of these antigens - LRRC50 and ESCO1, were also significantly overexpressed in 25-60% of various cancers revealing them as novel members of the CT antigen category with potential application in immunotherapy.