Effect of carboplatin-paclitaxel or -gemcitabine combinations on lung cancer cells spheroids
Background: Lung cancers represent the main cause of cancer related-death in the world. Recently, immunotherapy alone or in combination with chemotherapies have deeply impacted the therapeutic care leading to an improved overall survival. However, relapse will finally occur, with no efficient second line treatments so far. The development of new therapies based on comprehension of mechanisms of resistance is necessary. However, the difficulties to obtain tumor samples before and after first line treatment hampers to clearly understand the consequence of these molecules on tumor cells and then, to identify adapted second line therapies. Methods: To overcome this difficulty, we developed multicellular tumor spheroids (MCTS) using characterized Non-Small Cell Lung Cancer (NSCLC) cell lines, monocytes from healthy donors and fibroblasts (Human Foreskin Fibroblasts-2, HFF2). MCTS were treated with carboplatin-paclitaxel or -gemcitabine combinations according to clinic schedule of administration consisting on three repetitions of treatments (one combination and two single treatments (paclitaxel or gemcitabine)). The impact of treatments was studied using cell viability assay, histology, 3'RNA sequencing, real-time PCR, flow cytometry and confocal microscopy. Results: We showed that treatments induced a decrease of cell viability and strong modifications in the transcriptomic profile notably at the level of pathways involved in DNA damages repair and the cell cycle. Interestingly, we also observed a modification of the expression of genes considered as hallmarks of response/resistance to immune check point inhibitors and immunogenicity and particularly an increase of CD274 gene expression, coding for PD-L1. This result was validated at the protein level and showed to be restricted to tumor cells on MCTS containing fibroblasts and macrophages. This increase was also observed on an additional cell line, expressing low basal level of CD274. These results are consistent with previous observations on patients showing higher PD-L1 tumoral expression after chemotherapy exposure. Conclusions: This study shows that MCTS could be interesting models to study the impact of first line therapies using conditions close to the clinical practice and then, to identify more adapted second line or concomitant therapies for the treatment of lung cancers. Overall design: mRNA from control  (n=13), carboplatin-paclitaxel (n=5) or carboplatin-gemcitabine (n=5) treated MCTS were analyzed using 3'RNA sequencing 'X' correspond to 2 series of independent experiments CT is for control group (untreated) CaGe is for carboplatin-gemcitabine treated group CaPa is for carboplatin-paclitaxel treated group