Dual effects of the PI3K inhibitor ZSTK474 on multidrug efflux pumps in resistant cancer cells

ABCB1 and ABCG2 Overexpression Mediates Resistance to the Phosphatidylinositol 3-Kinase Inhibitor HS-173 in Cancer Cell Lines

Constitutive activation of the phosphoinositide-3-kinase (PI3K)/Akt signaling pathway is crucial for tumor growth and progression. As such, this pathway has been an enticing target for drug discovery. Although HS-173 is a potent PI3K inhibitor that halts cancer cell proliferation via G2/M cell cycle arrest, the resistance mechanisms to HS-173 have not been investigated. In this study, we investigated the susceptibility of HS-173 to efflux mediated by the multidrug efflux transporters ABCB1 and ABCG2, which are two of the most well-known ATP-binding cassette (ABC) transporters associated with the development of cancer multidrug resistance (MDR). We found that the overexpression of ABCB1 or ABCG2 significantly reduced the efficacy of HS-173 in human cancer cells. Our data show that the intracellular accumulation of HS-173 was substantially reduced by ABCB1 and ABCG2, affecting G2/M arrest and apoptosis induced by HS-173. More importantly, the efficacy of HS-173 in multidrug-resistant cancer cells could be recovered by inhibiting the drug-efflux function of ABCB1 and ABCG2. Taken together, our study has demonstrated that HS-173 is a substrate for both ABCB1 and ABCG2, resulting in decreased intracellular concentration of this drug, which may have implications for its clinical use.

Exploring synthetic lethal network for the precision treatment of clear cell renal cell carcinoma

The emerging targeted therapies have revolutionized the treatment of advanced clear cell renal cell carcinoma (ccRCC) over the past 15 years. Nevertheless, lack of personalized treatment limits the development of effective clinical guidelines and improvement of patient prognosis. In this study, large-scale genomic profiles from ccRCC cohorts were explored for integrative analysis. A credible method was developed to identify synthetic lethality (SL) pairs and a list of 72 candidate pairs was determined, which might be utilized to selectively eliminate tumors with genetic aberrations using SL partners of specific mutations. Further analysis identified BRD4 and PRKDC as novel medical targets for patients with BAP1 mutations. After mapping these target genes to the comprehensive drug datasets, two agents (BI-2536 and PI-103) were found to have considerable therapeutic potentials in the BAP1 mutant tumors. Overall, our findings provided insight into the overview of ccRCC mutation patterns and offered novel opportunities for improving individualized cancer treatment.

Advances in Immunosuppressive Agents Based on Signal Pathway

Immune abnormality involves in various diseases, such as infection, allergic diseases, autoimmune diseases, as well as transplantation. Several signal pathways have been demonstrated to play a central role in the immune response, including JAK/STAT, NF-κB, PI3K/AKT-mTOR, MAPK, and Keap1/Nrf2/ARE pathway, in which multiple targets have been used to develop immunosuppressive agents. In recent years, varieties of immunosuppressive agents have been approved for clinical use, such as the JAK inhibitor tofacitinib and the mTOR inhibitor everolimus, which have shown good therapeutic effects. Additionally, many immunosuppressive agents are still in clinical trials or preclinical studies. In this review, we classified the immunosuppressive agents according to the immunopharmacological mechanisms, and summarized the phase of immunosuppressive agents.

Exploiting the metabolic energy demands of drug efflux pumps provides a strategy to overcome multidrug resistance in cancer

BACKGROUND

P-glycoprotein (P-gp) is a prevalent resistance mediator and it requires considerable cellular energy to ensure ATP dependent efflux of anticancer drugs. The glycolytic pathway generates the majority of catabolic energy in cancer cells; however, the high rates of P-gp activity places added strain on its inherently limited capacity to generate ATP. This is particularly relevant for compounds such as verapamil that are believed to trap P-gp in a futile transport process that requires continuing ATP consumption. Ultimately, this leads to cell death and the hypersensitivity of resistant cells to verapamil is termed collateral sensitivity.

RESULTS

We show that the addition of verapamil to resistant cells produces a prominent reduction in ATP levels that supports the idea of disrupted energy homeostasis. Even in the absence of verapamil, P-gp expressing cells display near maximal rates of glycolysis and oxidative phosphorylation, which prevents an adequate response to the demand for ATP to sustain transport activity. Moreover, the near perpetually maximal rate of oxidative phosphorylation in the presence of verapamil resulted in elevated levels of reactive oxygen species that affect cell survival and underscore collateral sensitivity.

CONCLUSIONS

Our results demonstrate that the strained metabolic profiles of P-gp expressing resistant cancer cells can be overwhelmed by additional ATP demands.

GENERAL SIGNIFICANCE

Consequently, collateral sensitising drugs may overcome the resistant phenotype by exploiting, rather than inhibiting, the energy demanding activity of pumps such as P-gp.

Overexpression of ABCB1 and ABCG2 contributes to reduced efficacy of the PI3K/mTOR inhibitor samotolisib (LY3023414) in cancer cell lines

LY3023414 (samotolisib) is a promising new dual inhibitor of phosphoinositide 3-kinase (PI3K) and mammalian target of rapamycin (mTOR). Currently, multiple clinical trials are underway to evaluate the efficacy of LY3023414 in patients with various types of cancer. However, the potential mechanisms underlying acquired resistance to LY3023414 in human cancer cells still remain elusive. In this study, we investigated whether the overexpression of ATP-binding cassette (ABC) drug transporters such as ABCB1 and ABCG2, one of the most common mechanisms for developing multidrug resistance, may potentially reduce the efficacy of LY3023414 in human cancer cells. We demonstrated that the intracellular accumulation of LY3023414 in cancer cells was significantly reduced by the drug efflux function of ABCB1 and ABCG2. Consequently, the cytotoxicity and efficacy of LY3023414 for inhibiting the activation of the PI3K pathway and induction of G0/G1 cell-cycle arrest were substantially reduced in cancer cells overexpressing ABCB1 or ABCG2, which could be restored using tariquidar or Ko143, respectively. Furthermore, stimulatory effect of LY3023414 on the ATPase activity of ABCB1 and ABCG2, as well as in silico molecular docking analysis of LY3023414 binding to the substrate-binding pockets of these transporters provided additional insight into the manner in which LY3023414 interacts with both transporters. In conclusion, we report that LY3023414 is a substrate for ABCB1 and ABCG2 transporters implicating their role in the development of resistance to LY3023414, which can have substantial clinical implications and should be further investigated.

Synthesis and anticancer evaluation of novel 1H-benzo[d]imidazole derivatives of dehydroabietic acid as PI3Kα inhibitors

Phosphatidylinositol 3-kinase (PI3K) is one of the most attractive therapeutic targets for cancer treatment. In this study, a series of new 2-arylthio- and 2-arylamino-1H-benzo[d]imidazole derivatives of dehydroabietic acid were designed, synthesized and characterized by ¹H NMR, ¹³C NMR, IR and MS spectra analyses. In the in vitro anticancer assay, some title compounds showed significant inhibitory activities against four cancer cell lines (HCT-116, MCF-7, HeLa and HepG2). Among them, compound 9g exhibited the most potent activity with IC₅₀ values of 0.18 ± 0.03, 0.43 ± 0.05, 0.71 ± 0.08 and 0.63 ± 0.09 μM against four cancer cell lines, and considerably lower cytotoxicity to human gastric mucosal cell line Ges-1 (IC₅₀: 21.95 ± 0.73 μM). Besides, compound 9g displayed a certain selective activity to PI3Kα (IC₅₀ = 0.012 ± 0.002 μM) over PI3Kβ, γ and δ, and meanwhile, it can remarkably decrease the expression level of p-Akt (Ser473). In addition, compound 9g could increase intracellular reactive oxygen species level, decrease mitochondrial membrane potential, upregulate Bax and cleaved caspase-3/9 levels, downregulate Bcl-2 level and thus induce the apoptosis of HCT-116 cells in a dose-dependent manner. The results suggested that compound 9g could be considered as a promising PI3Kα inhibitor.

Synthesis and Pharmacological Evaluation of Noscapine-Inspired 5-Substituted Tetrahydroisoquinolines as Cytotoxic Agents

A series of 5-substituted tetrahydroisoquinolines was synthesized via a 10-step linear synthesis to assess whether replacement of noscapine's southern isobenzofuranone with other moieties resulted in retained cytotoxic activity. One such molecule, 18g, bearing a para-methoxybenzyl functionality with N-ethylcarbamoyl substitution, produced cell-cycle arrest at the G2/M phase with an EC₅₀ of 2.7 μM in the MCF-7 breast-cancer cell line, a 7-fold increase compared with that of noscapine (5). This molecule had similar activity (EC₅₀ of 2.5 μM) against the resistant NCI/Adr^RES cell line, demonstrating its potential to overcome or avert known resistance mechanisms, unlike current cytotoxic agents. Compound 18g was found to modify the drug-efflux activity of P-gp and, in combination studies, potentiate the antiproliferative activity of vinblastine. These results provide insights into structural modifications to noscapine that will guide future development toward more potent cytotoxic agents that are active against resistant cancer cells.