Immune checkpoint inhibitors modulate the cytotoxic effect of chemotherapy in lung adenocarcinoma cells

Abstract

Immunotherapy using immune checkpoint inhibitors (ICIs) has significantly improved survival in patients with non-small cell lung cancer (NSCLC), and ICIs are increasingly used in combination with cytotoxic treatments, such as chemotherapy. Although combined treatments are more effective, not all patients respond to the therapy; therefore, a detailed understanding of the effect of treatment combinations at the tumour level is needed. The present study aimed to explore whether ICIs could affect the cytotoxic effects of chemotherapy on lung adenocarcinoma cell lines with different PD-L1 expression levels (high, HCC-44; low, A-549). Using the resazurin-based assay, the efficacy of seven chemotherapeutic agents (cisplatin, etoposide, gemcitabine, pemetrexed, vinorelbine, docetaxel and paclitaxel) was compared in the presence or absence of the individually chosen single doses of four ICIs (nivolumab, pembrolizumab, atezolizumab and durvalumab). The results revealed that different ICIs can exhibit either potentiating or depotentiating effects, depending on the chemotherapy agent or lung adenocarcinoma cell line used. Durvalumab was the most promising ICI, which potentiated most chemotherapy agents in both cell lines, especially in the case of high PD-L1 expression. By contrast, nivolumab, exhibited depotentiating trends in several combinations. The immunostaining of γH2AX in treated cells confirmed that the potentiation of the chemotherapeutic cytotoxicity by durvalumab was at least partially mediated via increased DNA damage; however, this effect was strongly dependent on the chemotherapy agent and cell line used. Our future studies aim to address the specific mechanisms underlying the observed ICI-induced potentiation or depotentiation.

Exploring the Molecular Players behind the Potentiation of Chemotherapy Effects by Durvalumab in Lung Adenocarcinoma Cell Lines

“…The relatively high number of the listed proteins and the similar pattern of the count distributions in the different samples indicate that the treatment conditions were chosen appropriately (i.e., the extent of cellular death following exposure to cytotoxic compounds was not overly high). Although the lysis protocol used resulted in preferential enrichment for cytosolic rather than membranous proteins, we could identify PD-L1 in 7 out of 15 HCC-44 samples, yet in only 1 out of 15 A549 samples—which is consistent with the previously reported characteristics of the cell lines [ 8 ]. In addition, we could detect the fragments of the IgG light chain (k chain V-III region B6 and/or k chain C region) in all samples treated with durvalumab.…”

“…Still, the patients’ benefit from the ICI therapy as well as chemotherapy–ICI combinations has been somewhat limited, necessitating detailed studies on the pattern of the molecular players that might impact the efficacy of such therapies—taking into consideration not only the immune system component but also the tumor itself. This work represents a continuation of our previous studies [ 8 , 34 ] focusing on the investigation of ICI effects and the effect-mediating molecular mechanisms at the level of tumors.…”

“…For our experiments, we chose the same lung adenocarcinoma cell lines as those used in our previous study—HCC-44 and A549, featuring strong and weak PD-L1 positivity, respectively [ 8 ]. For the treatment mixtures, two chemotherapy agents were applied: cisplatin, the most widely used drug in NSCLC platinum-doublet treatment, and pemetrexed, which has been mostly used as a monotherapy [ 4 ].…”

“…Previously, we showed that different ICIs can either potentiate or depotentiate the cytotoxicity of chemotherapeutic agents in vitro, depending on the individual agent and the lung adenocarcinoma cell line used. By using γH2AX as a DNA damage marker, we have also shown previously that such potentiation may occur via the augmentation of the chemotherapy-induced DNA damage; however, this mechanism was not universal for all agents or cell lines tested [ 8 ]. The results of this study offer a mechanistic explanation of the previously published results.…”

“…Previously, we have reported the results of extensive screening of seven different chemotherapeutics in the presence or absence of four different ICIs in two cell lines, HCC-44 (high expression levels of PD-L1) and A549 (low expression levels of PD-L1) [ 8 ]. Among the tested ICIs, durvalumab showed the most pronounced chemotherapy-potentiating effect, yet also highlighted differences between the used cell lines and the chemotherapeutic drugs.…”