###### Abstract  
Cisplatin is one of the most effective anticancer agents used to treat colon cancer, which is the third malignancy between the most common human cancers in the world, but the resistance developed represents an obstacle against the full success of chemotherapy. An emerging interest appeared in finding other metallic compounds, such as ruthenium(III) complexes, for chemotherapeutic application in cancer. Our study focused on the anticancer activity of several ruthenium (Ru) complexes with quinolone antibiotics in colon tumor cell cultures. Real-time cell analysis and drug-mediated cytotoxicity tests monitored the inhibitory effects in the drug-treated LoVo colon cancer cells. Flow cytometry assays were performed to evaluate cell cycle phases distribution and apoptotic events. The obtained results showed dose-dependent increased levels of cell lysis and induction of apoptosis in LoVo cancer cells treated with the Ru(III) complexes. In addition, data showed a major decrease in cell proliferation, since the percentages of cells distributed in the S cell cycle phase diminished, and a G0/G1 cell arrest was observed. Therefore, our results strongly suggest that the newly synthesized Ru(III) complexes might play an important role in future chemotherapeutic approaches, since their activity is based on diminishing cell proliferation, induction of apoptosis, and modulation of cell cycle phases. r 2021 2  
it involves the loss of genomic stability that promotes the acquisition of further DNA alterations leading to cell transformation and tumor progression [4; 5], aberrant progression of the cell cycle, resistance to growth inhibition, proliferation without dependence on growth factors, replication without limit, evasion of apoptosis, induction of angiogenesis, and modification of cell adhesion [3; 6; 7]. Although many types of cancers are initially susceptible to chemotherapy, over time, they can develop drug resistance that often leads to therapeutic failure. Resistance to chemotherapy and molecularly targeted therapies is a major problem facing current cancer research [8; 9], and the number of drugs that have been shown to induce resistance in cancer cell killing is rapidly increasing, possibly through the modulation of survival cell components, such as proliferative or anti-apoptotic proteins [10; 11; 12]. The mechanisms of resistance to \"classical\" cytotoxic chemotherapeutics and to therapies that are designed to be selective for specific molecular targets share many features, such as alterations in the drug target, activation of pro-survival pathways, and ineffective induction of cell death [13; 14; 15]. The multi-drug combination chemotherapy was established to be a successful strategy in the management of colon cancer treatment, the reason being the potential additive or synergistic tumor cytotoxicity produced. Since the discovery of the cytotoxic properties of the cisplatin, platinum-based drugs have been investigated for cancer treatment and represent some of the most widely used anticancer chemotherapeutics, but their high toxicity and chemoresistance had spun the researchers to search for other novel chemotherapules based on metal compounds. In addition to cisplatin (CisPt), oxaliplatin and carboplatin are some of the most effective therapeutic agents commonly used in the treatment of colorectal cancers. [16; 17]. The mechanism of action of CisPt has been linked to its ability to crosslink with the purine bases on DNA, and the CisPt-DNA adducts formed might interfere with normal DNA replication and transcription and subsequently promote the activation of cellular apoptosis [18; 19]. Due to their potent cytotoxicity in cancer cells, ruthenium complexes have attracted great interest and recently emerged as potential candidates to replace platinum chemotherapy [19; 20; 21]. Over the last few years, research in colon cancer treatment has been focused on finding better chemotherapeutics.