Novel flexible heteroarotinoid, SL-1-39, inhibits HER2-positive breast cancer cell proliferation by promoting lysosomal degradation of HER2

Anchoring of hyaluronan glycocalyx to CD44 reduces sensitivity of HER2-positive gastric cancer cells to trastuzumab

Trastuzumab is widely used in human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC) therapy, but ubiquitous resistance limits its clinical application. In this study, we first showed that CD44 antigen is a significant predictor of overall survival for patients with HER2-positive GC. Next, we found that CD44 could be co-immunoprecipitated and co-localized with HER2 on the membrane of GC cells. By analyzing the interaction between CD44 and HER2, we identified that CD44 could upregulate HER2 protein by inhibiting its proteasome degradation. Notably, the overexpression of CD44 could decrease the sensitivity of HER2-positive GC cells to trastuzumab. Further mechanistic study showed that CD44 upregulation could induce its ligand, hyaluronan (HA), to deposit on the cancer cell surface, resulting in covering up the binding sites of trastuzumab to HER2. Removing the HA glycocalyx restored sensitivity of the cells to trastuzumab. Collectively, our findings suggested a role for CD44 in regulating trastuzumab sensitivity and provided novel insights into HER2-targeted therapy.

Valency and affinity control of aptamer-conjugated nanoparticles for selective cancer cell targeting

Nanoparticles (NPs) are commonly functionalized using targeting ligands to drive their selective uptake in cells of interest. Typical target cell types are cancer cells, which often overexpress distinct surface receptors that can be exploited for NP therapeutics. However, these targeted receptors are also moderately expressed in healthy cells, leading to unwanted off-tumor toxicities. Multivalent interactions between NP ligands and cell receptors have been investigated to increase the targeting selectivity towards cancer cells due to their non-linear response to receptor density. However, to exploit the multivalent effect, multiple variables have to be considered such as NP valency, ligand affinity, and cell receptor density. Here, we synthesize a panel of aptamer-functionalized silica-supported lipid bilayers (SSLB) to study the effect of valency, aptamer affinity, and epidermal growth factor receptor (EGFR) density on targeting specificity and selectivity. We show that there is an evident interplay among those parameters that can be tuned to increase SSLB selectivity towards high-density EGFR cells and reduce accumulation at non-tumor tissues. Specifically, the combination of high-affinity aptamers and low valency SSLBs leads to increased high-EGFR cell selectivity. These insights provide a better understanding of the multivalent interactions of NPs with cells and bring the nanomedicine field a step closer to the rational design of cancer nanotherapeutics.

Enantiomer of the novel flexible heteroarotinoid, SL-1-09, blocks cell cycle progression in breast cancer cells

Flexible heteroarotinoids (Flex-Hets) are compounds with promising anti-cancer activities. SHetA2, a first-generation Flex-Het, has been shown to inhibit the growth of cervical, head and neck, kidney, lung, ovarian, prostate, and breast cancers. However, SHetA2's high lipophilicity, limited selectivity, low oral bioavailability, and complicated synthesis has led to the development of second-generation compounds, such as 1-(1-(naphthalen-1-yl)ethyl)-3-(4-nitrophenyl) thiourea or SL-1-09. Results from our lab show that SL-1-09 exhibits anti-cancer activities against ERα+ and ERα- breast cancer cells at micromolar concentrations. SL-1-09 is a mixture of two enantiomers, R and S. The objective of this study was to further analyze these enantiomers to determine their individual anti-cancer activities. Cell cycle analysis demonstrated that the percentage of cells in S-phase is reduced significantly when breast cancer cell lines MCF-7, T47D and MDA-MB-453 cells are treated with 5.0 μM of the S enantiomer. Consistent with this finding, treatment of these cells with the S enantiomer resulted in lower expression levels of cell cycle proteins. Overall, our data indicate that the S enantiomer shows greater growth inhibitory effects than the R form against ERα+ (MCF7 and T47D) and ERα- (MDA-MB-453) breast cancer cells, suggesting that the activity observed in SL-1-09 is most likely due to the ability of the S enantiomer to block cell cycle progression.