G-quadruplex inducer/stabilizer pyridostatin targets SUB1 to promote cytotoxicity of a transplatinum complex

Pyridostatin (PDS) is a well-known G-quadruplex (G4) inducer and stabilizer, yet its target genes have remained unclear. Herein, combining mass spectrometry based proteomics strategy with bioinformatics analysis, we revealed that PDS significantly downregulated 22 proteins, of which the genes contain rich G4 potential sequences, in HeLa cancer cells, consequently upregulating 16 proteins remarkably. The PDS-regulated proteins appeared to work synergistically to activate cyclin and cell cycle regulation, and to restrain the inhibition of ARE-mediated mRNA decay pathway, suggesting that PDS itself is not a potential anticancer agent, at least towards HeLa cancer. Importantly, among the PDS targeted genes, SUB1, which expresses the human positive cofactor and DNA lesion sensor PC4, was down-regulated by 4.76-fold. Further studies demonstrated that the downregulation of PC4 dramatically promoted the cytotoxicity of trans-[PtCl2(NH3)(thiazole)] towards HeLa cells to a similar level to that of cisplatin, contributable to retarding the repair of 1,3-trans-platinated DNA lesion mediated by PC4. These findings not only provide new insights into better understanding on the biological functions of PDS, but also implicate a strategy for the rational design of novel multi-targeting platinum anticancer drugs via conjugation of PDS as a ligand to the coordination scaffold of transplatin for battling drug resistance to cisplatin.

Monofunctional Platinum(II) Anticancer Agents

Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side effects. Much effort has been made to circumvent the drug resistance and general toxicity of these drugs. Among multifarious designs, monofunctional platinum(II) complexes with a general formula of [Pt(3A)Cl]+ (A: Ammonia or amine) stand out as a class of “non-traditional” anticancer agents hopeful to overcome the defects of current platinum drugs. This review aims to summarize the development of monofunctional platinum(II) complexes in recent years. They are classified into four categories: fluorescent complexes, photoactive complexes, targeted complexes, and miscellaneous complexes. The intention behind the designs is either to visualize the cellular distribution, or to reduce the side effects, or to improve the tumor selectivity, or inhibit the cancer cells through non-DNA targets. The information provided by this review may inspire researchers to conceive more innovative complexes with potent efficacy to shake off the drawbacks of platinum anticancer drugs.

The Protein-Binding Behavior of Platinum Anticancer Drugs in Blood Revealed by Mass Spectrometry

Cisplatin and its analogues are widely used as chemotherapeutic agents in clinical practice. After being intravenously administrated, a substantial amount of platinum will bind with proteins in the blood. This binding is vital for the transport, distribution, and metabolism of drugs; however, toxicity can also occur from the irreversible binding between biologically active proteins and platinum drugs. Therefore, it is very important to study the protein-binding behavior of platinum drugs in blood. This review summarizes mass spectrometry-based strategies to identify and quantitate the proteins binding with platinum anticancer drugs in blood, such as offline high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC–ICP-MS) combined with electrospray ionization mass spectrometry (ESI-MS/MS) and multidimensional LC–ESI-MS/MS. The identification of in vivo targets in blood cannot be accomplished without first studying the protein-binding behavior of platinum drugs in vitro; therefore, relevant studies are also summarized. This knowledge will further our understanding of the pharmacokinetics and toxicity of platinum anticancer drugs, and it will be beneficial for the rational design of metal-based anticancer drugs.