Design, synthesis, and in vitro evaluation of BP-1-102 analogs with modified hydrophobic fragments for STAT3 inhibition

Twelve novel analogs of STAT3 inhibitor BP-1-102 were designed and synthesised with the aim to modify hydrophobic fragments of the molecules that are important for interaction with the STAT3 SH2 domain. The cytotoxic activity of the reference and novel compounds was evaluated using several human and two mouse cancer cell lines. BP-1-102 and its two analogs emerged as effective cytotoxic agents and were further tested in additional six human and two murine cancer cell lines, in all of which they manifested the cytotoxic effect in a micromolar range. Reference compound S3I-201.1066 was found ineffective in all tested cell lines, in contrast to formerly published data. The ability of selected BP-1-102 analogs to induce apoptosis and inhibition of STAT3 receptor-mediated phosphorylation was confirmed. The structure–activity relationship confirmed a demand for two hydrophobic substituents, i.e. the pentafluorophenyl moiety and another spatially bulky moiety, for effective cytotoxic activity and STAT3 inhibition.

Induction, regulation and roles of neural adhesion molecule L1CAM in cellular senescence

Aging involves tissue accumulation of senescent cells (SC) whose elimination through senolytic approaches may evoke organismal rejuvenation. SC also contribute to aging-associated pathologies including cancer, hence it is imperative to better identify and target SC. Here, we aimed to identify new cell-surface proteins differentially expressed on human SC. Besides previously reported proteins enriched on SC, we identified 78 proteins enriched and 73 proteins underrepresented in replicatively senescent BJ fibroblasts, including L1CAM, whose expression is normally restricted to the neural system and kidneys. L1CAM was: 1) induced in premature forms of cellular senescence triggered chemically and by gamma-radiation, but not in Ras-induced senescence; 2) induced upon inhibition of cyclin-dependent kinases by p16^INK4a; 3) induced by TGFbeta and suppressed by RAS/MAPK(Erk) signaling (the latter explaining the lack of L1CAM induction in RAS-induced senescence); and 4) induced upon downregulation of growth-associated gene ANT2, growth in low-glucose medium or inhibition of the mevalonate pathway. These data indicate that L1CAM is controlled by a number of cell growth- and metabolism-related pathways during SC development. Functionally, SC with enhanced surface L1CAM showed increased adhesion to extracellular matrix and migrated faster. Our results provide mechanistic insights into senescence of human cells, with implications for future senolytic strategies.

Distinct phenotypes and 'bystander' effects of senescent tumour cells induced by docetaxel or immunomodulatory cytokines

Cellular senescence is the process of the permanent proliferative arrest of cells in response to various inducers. It is accompanied by typical morphological changes, in addition to the secretion of bioactive molecules, including proinflammatory cytokines and chemokines [known as the senescence-associated secretory phenotype (SASP)]. Thus, senescent cells may affect their local environment and induce a so-called ‘bystander’ senescence through the state of SASP. The phenotypes of senescent cells are determined by the type of agent inducing cellular stress and the cell lineages. To characterise the phenotypes of senescent cancer cells, two murine cell lines were employed in the present study: TC-1 and B16F10 (B16) cells. Two distinct senescence inductors were used: Chemotherapeutic agent docetaxel (DTX) and a combination of immunomodulatory cytokines, including interferon γ (IFNγ) and tumour necrosis factor α (TNFα). It was demonstrated that DTX induced senescence in TC-1 and B16 tumour cell lines, which was demonstrated by growth arrest, positive β-galactosidase staining, increased p21^Waf1 (p21) expression and the typical SASP capable of inducing a ‘bystander’ senescence. By contrast, treatment with a combination of T helper cell 1 cytokines, IFNγ and TNFα, induced proliferation arrest only in B16 cells. Despite the presence of certain characteristic features resembling senescent cells (proliferation arrest, morphological changes and increased p21 expression), these cells were able to form tumours in vivo and started to proliferate upon cytokine withdrawal. In addition, B16 cells were not able to induce a ‘bystander’ senescence. In summary, the present study described cell line- and treatment- associated differences in the phenotypes of senescent cells that may be relevant in optimization of cancer chemo- and immunotherapy.

Tumor growth accelerated by chemotherapy-induced senescent cells is suppressed by treatment with IL-12 producing cellular vaccines

Standard-of-care chemo- or radio-therapy can induce, besides tumor cell death, also tumor cell senescence. While senescence is considered to be a principal barrier against tumorigenesis, senescent cells can survive in the organism for protracted periods of time and they can promote tumor development. Based on this emerging concept, we hypothesized that elimination of such potentially cancer-promoting senescent cells could offer a therapeutic benefit. To assess this possibility, here we first show that tumor growth of proliferating mouse TC-1 HPV-16-associated cancer cells in syngeneic mice becomes accelerated by co-administration of TC-1 or TRAMP-C2 prostate cancer cells made senescent by pre-treatment with the anti-cancer drug docetaxel, or lethally irradiated. Phenotypic analyses of tumor-explanted cells indicated that the observed acceleration of tumor growth was attributable to a protumorigenic environment created by the co-injected senescent and proliferating cancer cells rather than to escape of the docetaxel-treated cells from senescence. Notably, accelerated tumor growth was effectively inhibited by cell immunotherapy using irradiated TC-1 cells engineered to produce interleukin IL-12. Collectively, our data document that immunotherapy, such as the IL-12 treatment, can provide an effective strategy for elimination of the detrimental effects caused by bystander senescent tumor cells in vivo.