Targeting G1-S phase cell-cycle alterations with CDK4/6 inhibitor-based genomically matched personalized therapy approach.

3623 Background: Although CDK4/6 inhibitors are established as a standard treatment option for hormone receptor-positive, HER2-negative metastatic breast cancer patients, its benefit in other solid tumors is unclear. Moreover, no clear biomarker exists that predicts the response to CDK4/6 inhibitors. Herein, we investigated the factors associated with clinical outcomes from CDK4/6 inhibitor-based therapy, used alone or in combination with other therapies targeting genomic co-alterations, among diverse cancer patients with potentially sensitizing alterations in G1-S phase cell-cycle alterations (defined as CDK4/6 amplifications, CCND1/2/3 amplifications or CDKN2A/ B alterations). Methods: We interrogated molecular profiles of 2,457 patients with diverse solid tumors for G1-S phase cell-cycle alterations and co-altered genes using clinical-grade next generation sequencing (182-465 genes). Results: G1-S phase cell-cycle alterations occurred in 20.6% (507/2,457) of patients with 99% of those with cell cycle alterations (N = 501/507) harboring at least one characterized co-alteration (median, 4; range, 0-24). Significant improvement in median PFS was observed when CDK4/6 inhibitor-based therapies matched a larger proportion of tumor alterations, often by being given together with other drugs that were matched to genomic co-alterations, hence achieving a high Matching Score (high Matching Score [≥50%] vs. low Matching Score [ < 50%]: all cohorts including breast cancer [N = 58]: PFS: 6.2 vs. 3.2 months, P = 0.001; non-breast cancer cohort [N = 40]: PFS 6.2 vs. 2.0 months, P < 0.001 [multivariate]). (Matching Score roughly equivalent to number of alterations targeted divided by total number of characterized alterations). In contrast, targeting CDK4/6 alone in patients harboring cell-cycle pathway alterations along with other co-alterations, without targeting the genomic co-alterations, did not improve PFS even in patients who received matched CDK4/6 inhibitors as part of a combination regimen. Representative cases that were successfully treated with a matched combination strategy will also be presented. Conclusions: Most patients with G1-S phase cell-cycle alterations harbored co-genomic alterations. Our current study suggests that targeting co-alterations along with cell cycle molecular alterations may be necessary to achieve better clinical outcome. Further clinical investigation with larger numbers of patients are required.

Unravelling the Potential Cytotoxic Effects of Metal Oxide Nanoparticles and Metal(Loid) Mixtures on A549 Human Cell Line

Humans are typically exposed to environmental contaminants’ mixtures that result in different toxicity than exposure to the individual counterparts. Yet, the toxicology of chemical mixtures has been overlooked. This work aims at assessing and comparing viability and cell cycle of A549 cells after exposure to single and binary mixtures of: titanium dioxide nanoparticles (TiO2NP) 0.75–75 mg/L; cerium oxide nanoparticles (CeO2NP) 0.75–10 μg/L; arsenic (As) 0.75–2.5 mg/L; and mercury (Hg) 5–100 mg/L. Viability was assessed through water-soluble tetrazolium (WST-1) and thiazolyl blue tetrazolium bromide (MTT) (24 h exposure) and clonogenic (seven-day exposure) assays. Cell cycle alterations were explored by flow cytometry. Viability was affected in a dose- and time-dependent manner. Prolonged exposure caused inhibition of cell proliferation even at low concentrations. Cell-cycle progression was affected by TiO2NP 75 mg/L, and As 0.75 and 2.5 μg/L, increasing the cell proportion at G0/G1 phase. Combined exposure of TiO2NP or CeO2NP mitigated As adverse effects, increasing the cell surviving factor, but cell cycle alterations were still observed. Only CeO2NP co-exposure reduced Hg toxicity, translated in a decrease of cells in Sub-G1. Toxicity was diminished for both NPs co-exposure compared to its toxicity alone, but a marked toxicity for the highest concentrations was observed for longer exposures. These findings prove that joint toxicity of contaminants must not be disregarded.

Cell cycle alterations in the mussel Mytilus galloprovincialis hemocytes caused by environmental contamination

Environmental contamination includes a mixture of organic substances that can have detrimental effects on marine organisms and should be evaluated in the quality and risk assessment of investigated marine areas. Marine areas selected for this study are a protected area, a mariculture area, a shipyard and an industrial area. Based on the toxicity of the organic seawater extracts these areas were classified as an undisturbed reference area (S1), an area with the low anthropogenic impact (S2), a potentially endangered area (S3) and an area with high anthropogenic impact (S4) respectively. The organic mixtures present in seawater samples collected at the above defined areas were tested for the induction of DNA damage and cell cycle alterations in the mussel Mytilus galloprovincialis hemocytes. Flow cytometric analyses were performed to detect changes in hemocytes DNA content distribution throughout the cell cycle. Organic seawater extracts from sampling sites S2, S3 and S4 induced an increase in the coefficient of variation of the G0/G1 peak and an increase in the number of cells in the G2/M phase reflecting the extent of DNA damage and G2/M arrest, respectively. The G2/M arrest in mussel hemocytes was concentration-dependent upon injection with organic seawater extracts from the S3 site and time dependant for S2, S3 and S4 sampling sites. The time dependence of the induction of the G/M arrest showed a characteristic pattern for each site due to the different quantitative and qualitative composition of the organic seawater extracts. The G2/M arrest was reversible 24 or 72 hours after treatment with organic seawater extracts from S2 or S3, and S4 sites, respectively. This reversibility was time- and site-specific indicating that such DNA damage is repairable to a certain degree according to the organic seawater extract composition. Thus, the hemocytes cell cycle alterations in the mussel Mytilus galloprovincialis caused by organic seawater extracts reliably reflect the extent of organic contamination effects for selected marine areas.