Temporal regulation of gene expression and pathways in chemotherapy-induced senescence in HeLa cervical cancer cell line.

Cellular senescence is the state of permanent growth arrest. Chemotherapeutic drugs induce senescence, known as therapy-induced senescence. Although there are studies deciphering processes in senescence, more studies providing detailed information on therapy-induced senescence at the transcriptome level are needed. In order to understand temporal molecular changes of doxorubicin treatment in the course of senescence formation, two data sets from HeLa cells at 16 h and 72 h doxorubicin treatment were analyzed. GO BP enrichment, KEGG pathways and hub genes specific to or shared between 16 h and 72 h doxorubicin treated HeLa cells were identified. Genes functioning in p53 signaling were upregulated only in 16 h, while genes functioning in extracellular matrix organization were upregulated only in 72 h doxorubicin treated HeLa cells. Wound healing genes were gradually upregulated from 16 h to 72 h doxorubicin treatment and metabolic pathways were downregulated at both. ncRNA processing and ribosome biogenesis GO BP terms were enriched in upregulated genes at 16 h, while these terms were enriched in downregulated genes at 72 h senescent HeLa cells. According to our results, genes functioning in p53 signaling may be involved in the induction of senescence, but may not be required to maintain senescence in HeLa cells.

Senescent cells and SASP in cancer microenvironment: New approaches in cancer therapy.

Cellular senescence was first described as a state characterized by telomere shortening, resulting in limiting cell proliferation in aging. Apart from this type of senescence, which is called replicative senescence, other senescence types occur after exposure to different stress factors. One of these types of senescence induced after adjuvant therapy (chemotherapy and radiotherapy) is called therapy-induced senescence. The treatment with chemotherapeutics induces cellular senescence in normal and cancer cells in the tumor microenvironment. Thus therapy-induced senescence in the cancer microenvironment is accepted one of the drivers of tumor progression. Recent studies have revealed that senescence-associated secretory phenotype induction has roles in pathological processes such as inducing epithelial-mesenchymal transition and promoting tumor vascularization. Thus senolytic drugs that specifically kill senescent cells and senomorphic drugs that inhibit the secretory activity of senescent cells are seen as a new approach in cancer treatment. Developing and discovering new senotherapeutic agents targeting senescent cells is also gaining importance. In this review, we attempt to summarize the signaling pathways regarding the metabolism, cell morphology, and organelles of the senescent cell. Furthermore, we also reviewed the effects of SASP in the cancer microenvironment and the senotherapeutics that have the potential to be used as adjuvant therapy in cancer treatment.

The implication of ROCK 2 as a potential senotherapeutic target via the suppression of the harmful effects of the SASP: Do senescent cancer cells really engulf the other cells?

Chemotherapy-induced senescent cancer cells secrete several factors in their microenvironment called SASP. Accumulated evidence states that SASP is responsible for some of the harmful effects of chemotherapy such as drug resistance and the induction of cancer cell proliferation, migration, and invasion. Therefore, to develop senolytic and/or senomorphic drugs, targeting the senescent cells gains importance as a new strategy for preventing the damage that senescent cancer cells cause. In the current work, we evaluated whether Rho/Rho kinase pathway has the potential to be used as a target pathway for the development of senolytic and/or senomorphic drugs in doxorubicin-induced senescent cancer cell lines. We have determined that inhibition of Rho/Rho kinase pathway with CT04 and Y27632 reduced the secretory activity of senescent cancer cells and changed the composition of SASP. Our results indicate that ROCK 2 isoform was responsible for these observed effects on the SASP. In addition, non-senescent cancer cell proliferation and migration accelerated by senescent cells were set back to the pre-induction levels after ROCK inhibition. Moreover, contrary to the previous observations, another important finding of the current work is that senescent HeLa and A549 cells did not engulf the non-senescent HeLa, A549 cells, and non-cancer HUVEC. These results indicate that ROCK inhibitors, in particular ROCK 2 specific inhibitors, have the potential to be developed as novel senomorphic drugs. In addition, we found that all senescent cancer cells do not share the same engulfment ability, and this process should not be generalized.

Antimigratory effect of pyrazole derivatives through the induction of STAT1 phosphorylation in A549 cancer cells.

OBJECTIVES: In cancer treatment, it is important to prevent or slow down metastasis as well as preventing the proliferation of cancer cells. In this study, we aimed to find pyrazole compounds with antimigratory properties. METHODS: The 'PASSonline' programme was used to determine the possible pharmacological activities of the pyrazole compounds selected from the library, and two pyrazole derivatives were identified as a transcription factor STAT inhibitor with a high probability. There are studies known that JAK/STAT pathway is related to cancer cell migration, thus the possible antimigratory effects of these two synthesized pyrazole compounds were examined in A549 cancer cells. KEY FINDINGS: Our data demonstrated that compound-2 at different concentrations significantly inhibited cell migration in A549 cells. Then, the effects of these compounds on STAT activation were evaluated. We reported that 10 µM compound-2 induced a significant phosphorylation of STAT1 suggesting that STAT1 activation may be responsible for the antimigratory effect of compound-2. CONCLUSIONS: Taken together, the compound-2 is a promising compound with the antimigratory activity for cancer treatment, and further studies are needed to synthesize more active derivatives by evaluating the structure-activity relationship of leading compound-2.

A novel proteolytic cleavage of ROCK 1 in cell death: Not only by caspases 3 and 7 but also by caspase 2.

During apoptosis, myosin light chain phosphorylation induced by ROCK 1, activated by caspase 3-mediated cleavage, results in the formation of membrane blebs. Additionally, actin-myosin-based contraction induced by the activation of ROCK is involved in the apoptotic nuclear disintegration. In previous studies, it was reported that ROCK 1 was only cleaved by caspase 3 in cell death and caspase 7 was involved in truncation of ROCK 1 in in-vitro cell-free conditions. Here we reported that caspase 2 is involved in the truncation of ROCK 1 directly as well as caspase 3 and caspase 7. Utilizing caspase 3-deficient MCF-7, MDA-MB-231 and HeLa cells, we demonstrated that caspase 2 produced an active fragment of approximately 130 kDa of ROCK 1 in cell death. The cleaved active fragment of ROCK 1 is also responsible for the formation of membrane blebbing in cell death. Interestingly, caspase 2-mediated cleavage of ROCK 1 might occur in the region where caspase 3 truncates ROCK 1. Moreover, the presence of an active cleaved form of ROCK 1 in the nuclei implies that this fragment might play a role in the disruption of nuclear integrity. Taken together, it was determined that caspase 2 has a role in the truncation of ROCK 1 in cell death, and a new activation mechanism has been defined for ROCK 1.