Sulfonate Version of OHPAS Linker Has Two Distinct Pathways of Breakdown: Elimination Route Allows Para-Hydroxy-Protected Benzylsulfonate (PHP-BS) to Serve as an Alternative Self-Immolative Group.

Recently we have reported that the ortho-hydroxy-protected aryl sulfate (OHPAS) system can be exploited as a new self-immolative group (SIG) for phenolic payloads. We extended the system to nonphenolic payloads by simply introducing a para-hydroxy benzyl (PHB) spacer. As an additional variation of the system, we explored a benzylsulfonate version of the OHPAS system and found that it has two distinct breakdown pathways, cyclization and 1,4-elimination, the latter of which implies that para-hydroxy-protected (PHP) benzylsulfonate (BS) can also be used as an alternative SIG. The PHP-BS system was found to be stable chemically and in mouse and human plasma, having payload release rates comparable to those of the original OHPAS conjugates.

Introduction of Para-Hydroxy Benzyl Spacer Greatly Expands the Utility of Ortho-Hydroxy-Protected Aryl Sulfate System: Application to Nonphenolic Payloads.

The ortho-hydroxy-protected aryl sulfate (OHPAS) linker is composed of a diaryl sulfate backbone equipped with a latent phenol moiety at the ortho position of one of the aryl units. The Ar-OH released when the ortho phenol undergoes intramolecular cyclization and displaces the second aryl unit can be viewed as a payload. We have shown in the preceding paper that the OHPAS linkers are highly stable chemically and in various plasmas, yet release payloads when exposed to suitable triggering conditions. As an extension of the OHPAS system, we employed a para-hydroxy benzyl (PHB) spacer for coupling to nonphenolic payloads; this tactic again provided a highly stable system capable of smooth release of appended payloads. The PHB modification works beautifully for tertiary amine and N-heterocycle payloads.

Role of TOPK in lipopolysaccharide-induced breast cancer cell migration and invasion.

Inflammation has been known to be linked to invasion or metastasis of breast cancer, which has poor prognosis, although the regulatory mechanism remains to be undiscovered. Here we show that T-LAK cell-originated protein kinase (TOPK) mediates pro-inflammatory endotoxin lipopolysaccharide (LPS)-induced breast cancer cell migration and invasion. The mRNA or protein level of TOPK, toll- like receptor4 (TLR4), interleukin (IL)-6, vascular endothelial growth factor (VEGF) or matrix metalloproteinase9 (MMP9) genes related to TLR4 signaling or tumor progression was induced by LPS treatment in MCF7 breast cancer cells, but the induction was abolished by stable knocking down of TOPK in MCF7 cells. Also, TOPK depletion decreased LPS-induced phosphorylation of p38, but not ERK and JNK among mitogen-activated protein kinases (MAPKs). On the other hand, we revealed that TOPK is essential for transcriptional activity of NF-κB or MMP9 promoter triggered by LPS. The induced promoter activity of NF-κB or MMP9 but not AP-1 was inhibited by knocking down of TOPK. Furthermore, we demonstrated that inhibitor of TOPK or MMP9 as well as MMP9 siRNA efficiently blocked LPS-induced migration or invasion of breast cancer cell lines. Interestingly, both of expression of TOPK and TLR4 were markedly increased in high-grade breast cancer. Collectively, we conclude that TOPK functions as a key mediator of LPS/TLR4-induced breast cancer cell migration and invasion through regulation of MMP9 expression or activity, implying a potential role of TOPK as a therapeutic target linking LPS-induced inflammation to breast cancer development.