SASH1 mediates sensitivity of breast cancer cells to chloropyramine and is associated with prognosis in breast cancer

Abstract

Expression of the SASH1 protein is reduced in a range of human cancers and has been implicated in apoptotic cancer cell death. This study investigated whether increasing SASH1 expression could be a useful therapeutic strategy in breast cancer. Ectopic SASH1 expression increased apoptosis in 7/8 breast cancer cell lines. Subsequent in silico connectivity screening demonstrated that the clinically approved antihistamine drug, chloropyramine, increased SASH1 mRNA levels. Chloropyramine has previously been shown to have anti-tumour activity in breast cancer in part through modulation of FAK signalling, a pathway also regulated by SASH1. This study demonstrated that chloropyramine increased SASH1 protein levels in breast cancer cells. Consistent with this the agent reduced cell confluency in 7/8 cell lines treated irrespective of their ER status but not apoptosis incompetent MCF7 cells. In contrast SASH1 siRNA-transfected breast cancer cells exhibited reduced chloropyramine sensitivity. The prognostic significance of SASH1 expression was also investigated in two breast cancer cohorts. Expression was associated with favourable outcome in ER-positive cases, but only those of low histological grade/proliferative status. Conversely, we found a very strong inverse association in HER2+ disease irrespective of ER status, and in triple-negative, basal-like cases. Overall, the data suggest that SASH1 is prognostic in breast cancer and could have subtype-dependent effects on breast cancer progression. Pharmacologic induction of SASH1 by chloropyramine treatment of breast cancer warrants further preclinical and clinical investigation.

Correlation of SASH1 expression and ultrasonographic features in breast cancer

“…From the point of histologic type, there were no statistical differences in the positive rate of SASH1 expression when compared among groups of invasive ductal carcinoma, invasive lobular carcinoma, mucinous carcinoma, and invasive cribriform carcinoma. Burgess et al6 recently reported a significant difference in SASH1 expression between ER-positive and -negative breast cancers, but no statistical difference was found between human epidermal growth factor receptor 2 (HER2)-positive and -negative breast cancers.…”

“…Recently, Burgess et al reported that SASH1 had a subtype-dependent effect on the progression of breast cancer and was also associated with its prognosis. Restoring SASH1 protein expression in breast cancer cells through chloropyramine treatment seems to increase apoptosis in breast cancer cells, suggestive of its potential role as a therapeutic target 6. In addition, decreased expression of SASH1 is found in 74% of breast tumors compared with normal breast epithelial tissues 7…”

Expression of MAGE‐A and NY‐ESO‐1 cancer/testis antigens is enriched in triple‐negative invasive breast cancers

“…Tumour cell percentage staining was subsequently stratified as either >75% or <75%, as this adequately described the positive cases. IHC analysis was performed for the markers, the results for some of which have been published previously . The cut‐off value for HER2 positivity was based on a silver in‐situ hybridisation (SISH) score of >6 and an IHC score of 3+ if SISH was unsuccessful.…”

The discovery of new and more potent chloropyramine (C4) analogues for the potential treatment of invasive breast cancer

“…The results show that compound 5c has a very good aqueous solubility with estimated precipitation range 100 μ m (lower bound) and >100 μ m (upper bound), Table . This relatively high aqueous solubility could prove to be a possible solution to the sedation side‐effect of chloropyramine because of its ability to cross the blood brain barrier (BBB) . The calculated logP values ( C4 = 3.99, 5c = 4.42) are similar but tPSA values ( C4 = 18.84, 5c = 32.78) suggest that 5c is less likely to cross the BBB.…”

“…More recently, Burgess et al. have independently used in silico connectivity mapping and in vitro modelling to demonstrate that chloropyramine C4 , increased SASH1 protein levels in breast cancer cells . Expression of the SASH1 protein is reduced in a range of human cancers and has been implicated in apoptotic cancer cell death.…”