Author Correction: Macrophages confer resistance to PI3K inhibitor GDC-0941 in breast cancer through the activation of NF-κB signaling

PI3K Inhibitors in Cancer: Clinical Implications and Adverse Effects

The phospatidylinositol-3 kinase (PI3K) pathway is a crucial intracellular signaling pathway which is mutated or amplified in a wide variety of cancers including breast, gastric, ovarian, colorectal, prostate, glioblastoma and endometrial cancers. PI3K signaling plays an important role in cancer cell survival, angiogenesis and metastasis, making it a promising therapeutic target. There are several ongoing and completed clinical trials involving PI3K inhibitors (pan, isoform-specific and dual PI3K/mTOR) with the goal to find efficient PI3K inhibitors that could overcome resistance to current therapies. This review focuses on the current landscape of various PI3K inhibitors either as monotherapy or in combination therapies and the treatment outcomes involved in various phases of clinical trials in different cancer types. There is a discussion of the drug-related toxicities, challenges associated with these PI3K inhibitors and the adverse events leading to treatment failure. In addition, novel PI3K drugs that have potential to be translated in the clinic are highlighted.

Regulation of temozolomide resistance in glioma cells via the RIP2/NF-κB/MGMT pathway

Background

Temozolomide (TMZ) is a first‐line chemotherapy drug for the treatment of malignant glioma and resistance to it poses a major challenge. Receptor‐interacting protein 2 (RIP2) is associated with the malignant character of cancer cells. However, it remains unclear whether RIP2 is involved in TMZ resistance in glioma.

Methods

RIP2 expression was inhibited in TMZ‐resistant glioma cells and normal glioma cells by using small interfering RNA (siRNA) against RIP2. Plasmid transfection method was used to overexpress RIP2. Cell counting kit‐8 assays were performed to evaluate cell viability. Western blotting or immunofluorescence was performed to determine RIP2, NF‐κB, and MGMT expression in cells. Flow cytometry was used to investigate cell apoptosis. TMZ‐resistant glioma xenograft models were established to evaluate the role of the RIP2/NF‐κB/MGMT signaling pathway in drug resistance.

Results

We observed that RIP2 expression was upregulated in TMZ‐resistant glioma cells, whereas silencing of RIP2 expression enhanced cellular sensitivity to TMZ. Similarly, upon the induction of RIP2 overexpression, glioma cells developed resistance to TMZ. The molecular mechanism underlying the process indicated that RIP2 can activate the NF‐κB signaling pathway and upregulate the expression of O6‐methylguanine‐DNA methyltransferase (MGMT), following which the glioma cells develop drug resistance. In the TMZ‐resistant glioma xenograft model, treatment with JSH‐23 (an NF‐κB inhibitor) and lomeguatrib (an MGMT inhibitor) could enhance the sensitivity of the transplanted tumor to TMZ.

Conclusion

We report that the RIP2/NF‐κB/MGMT signaling pathway is involved in the regulation of TMZ resistance. Interference with NF‐κB or MGMT activity could constitute a novel strategy for the treatment of RIP2‐positive TMZ‐resistant glioma.

Physcion-8-O-β-d-glucoside interferes with the nuclear factor-κB pathway and downregulates P-glycoprotein expression to reduce paclitaxel resistance in ovarian cancer cells

OBJECTIVE

This study assessed whether physcion-8-O-beta-D-monoglucoside (PG) sensitises paclitaxel (PTX)-resistant ovarian cancer cells and explored the underlying mechanism.

METHODS

Ovarian cancer SK-OV-3 cells were used to establish PTX-resistant SK-OV-3 (SK-OV-3/PTX) cells. The Cell Counting Kit-8 assay and crystal violet staining were used to determine cell viability. P-glycoprotein (P-gp) and nuclear factor (NF)-κB expression and cell distributions were detected using immunofluorescence. Cell apoptosis and protein expression changes were detected using flow cytometry and western blotting, respectively. Effect of PG in vivo was evaluated using a xenograft tumour model. P-gp expression in tumour tissues was detected using immunohistochemical staining.

KEY FINDINGS

PG (1-10 μm) did not significantly affect SK-OV-3/PTX cell proliferation but significantly downregulated P-gp expression. PG pretreatment (1-10 μm) enhanced PTX cytotoxicity. PG treatment decreased the quantity of phosphorylated-NF-κB p65 in SK-OV-3/PTX cell total proteins and upregulated IKBα expression. Simultaneously, it decreased NF-κB p65 levels in nuclear proteins. PG (1-10 μm) inhibited NF-κB p65 entry into the nucleus. PTX plus PG significantly inhibited SK-OV-3/PTX xenograft tumour growth. PG (1-10 μm) reduced P-gp expression in transplanted tumour tissue.

CONCLUSIONS

PG can enhance the sensitivity of PTX-resistant ovarian cancer cells SK-OV-3/PTX to PTX, and this effect is related to inhibiting NF-κB from entering the nucleus and down-regulating the expression of P-gp protein.