# Calcium Sulfide Nanoclusters Trigger DNA Damage and Induce Cell Cycle Arrest in Non-Small-Cell Lung Adenocarcinoma Cells

## TL;DR

Calcium sulfide nanoclusters cause DNA damage and stop cancer cell division in lung cancer cells without harming healthy cells.

## Contribution

This study reveals the pH-dependent mechanism by which CaS nanoclusters selectively target lung cancer cells.

## Key findings

- CaS nanoclusters increase calcium and ROS levels, causing DNA damage in lung cancer cells.
- They selectively arrest cancer cells in the G0-G1 and S phases of the cell cycle.
- The effects are pH-dependent and occur in the acidic tumor microenvironment.

## Abstract

Lung cancer remains the most common malignancy independent of sex. Here, we focused on unraveling the molecular mechanisms of CaS nanoclusters inducing cytotoxicity by investigating DNA damage, the cell cycle, oxidative stress, and cellular repair mechanisms in non-small-cell lung carcinoma (NSCLC) cells compared to healthy lung fibroblasts. Our previous studies have demonstrated the therapeutic potential of calcium sulfide (CaS) nanostructures in skin and breast cancer models, leading to a significant reduction in cancer cell proliferation. However, how CaS nanoclusters enhance their therapeutic effects on cancer cells while minimizing damage to healthy cells remains unknown. Our results show that CaS nanoclusters, once dissociated into Ca2+ and H2S in an acidic microenvironment, selectively allow extracellular calcium to enter, leading to an increase in free calcium entry, triggering oxidative stress and limiting DNA repair mechanisms in NSCLC. Furthermore, CaS nanoclusters selectively arrest NSCLC cells in the G0-G1 and S phases of the cell cycle without affecting healthy cells’ cycles. Here, we also show that the selective effects of CaS nanoclusters on lung adenocarcinoma are less likely to be regulated by intrinsic apoptotic or mitochondrial pathways. They are, rather, caused by an increase in Ca2+ and ROS, causing double-stranded DNA breakages. This selectivity for malignant cells is pH-dependent because it occurs in the acidic microenvironment characteristic of these cells. Overall, this is the first piece of evidence that CaS disrupts genomic stability, prevents the replication of damaged cells, and ultimately influences cell fate decisions such as cell cycle arrest or cell death including mitotic catastrophe and necroptotic simultaneous events.