This interpretation is additional supported from the truth scientific assays that in our investigation, typical mitotic figures had been only observed exceptionally in etoposide exposed cells, whereas nuclei presenting atypical morphology were rather abundant. On top of that, the TUNEL optimistic cells have been more abundant right after treatment in comparison using the cells presenting biochemical features of cell death within the annexin V/PI assay. There exists clear evidence that endo polyploidization in senescent cell popula tion constitutes a consequence of re replication of ge nomically damaged G2/M cells. In the very same time, independent karyoplasts/reproductive genome lowered subcells may type from giant polyploid cells by means of some kind of reductional division, leading to increased gen etic variation.
What's far more, induction of DNA injury in cancer cell lines was established to be associated not only to endopolyploidy and depolyploidization, but in addition to overexpression of meiosis specific genes and mobili zation of their items to your websites strategic for division. More a short while ago it's also been reported that al even though you will discover some morphological and biochemical characteristics of senescence at the same time as growth arrest within the population of A549 cells exposed to topoisomerase II inhibitors, long-term effects from the therapy in clude a re development of the fraction of population originating most in all probability from cancer stem cells. Within this sit uation, a somewhat much more prolonged, but still rever sible development arrest on the population occurred soon after inhibition of your DNA harm response pathway.
On account of the truth that 24 h after exposure to etoposide we nevertheless observed a comparatively high amount of TUNEL good cells in comparison with those annexin V/PI beneficial, this pathway was most almost certainly lively in our experiment too. Therefore, some alterations in heterochromatin options, like gluey or stick heterochromatin in near senescent population of cultured cells, appear to be accountable for mitotic failure and chromosomal instability. Ana logically, etoposide may perhaps induce impairments in untan gling of chromatin, which in flip interferes using the right formation of chromosomes and also the decatenation of chromatids, leading most likely towards the identical ultimate outcome, i. e. induction of a senescent like pheno kind while in the cancer cell population as well as increased polyploidy and genetic instability, as well as heterogen eity with the response.
What is much more, an unstable senes cence plan induced in cancer cell populations by DNA damage is considered to get related to a phenomenon corresponding to your above described series of occasions, and termed neosis. The truth is this course of action could con tribute to chemotherapy resistance, on account of the truth that greater instability coupled with repeated cycles of self renewal may favour the accumulation of survival selling mutations as well as the growth of far more inva sive subclones, particularly underneath constant get in touch with which has a chemotherapeutic drug.