A novel protein-drug conjugate, SSH20, demonstrates significant efficacy in caveolin-1-expressing tumors

Abstract

In recent years, human serum albumin (HSA) has been characterized as an ideal drug carrier in the cancer arena. Caveolin-1 (Cav-1) has been established as the principal structural protein of caveolae and, thus, critical for caveolae-mediated endocytosis. Cav-1 has been shown to be overexpressed in cancers of the lung and pancreas, among others. We found that Cav-1 expression plays a critical role in both HSA uptake and response to albumin-based chemotherapies. As such, developing a novel albumin-based chemotherapy that is more selective for tumors with high Cav-1 expression or high levels of caveolar-endocytosis could have significant implications in biomarker-directed therapy. Herein, we present the development of a novel and effective HSA-SN-38 conjugate (SSH20). We find that SSH20 uptake decreases significantly by immunofluorescence assays and western blotting after silencing of Cav-1 expression through RNA interference. Decreased drug sensitivity occurs in Cav-1-depleted cells using cytotoxicity assays. Importantly, we find significantly reduced sensitivity to SSH20 in Cav-1-silenced tumors compared to Cav-1-expressing tumors in vivo . Notably, we show that SSH20 is significantly more potent than irinotecan in vitro and in vivo . Together, we have developed a novel HSA-conjugated chemotherapy that is potent, effective, safe, and demonstrates improved efficacy in high Cav-1-expressing tumors.

Improved Targeting and Safety of Doxorubicin through a Novel Albumin Binding Prodrug Approach

“…Pharmacokinetic studies have indicated doxorubicin has a very short half-life in the blood and is taken up by cardiac muscles. , It is well established that albumin, the most abundant protein in plasma, is a natural transporter of nutrients with a very high circulatory half-life of 19 days. Albumin-bound drugs are thought to be preferentially delivered to solid tumor cells due to the EPR effect and the amplified expression of albumin-binding proteins on the tumor endothelium and tumor cells. ,, In addition, tumor cells frequently overexpress Cav-1, which enhances the internalization of albumin-associated drugs through caveolae-mediated endocytosis. , The latter mechanism and other uptake mechanisms are likely to increase in a harsh, competitive tumor microenvironment as tumor cells scavenge nutrients. Herein, IPBA-Dox, a novel albumin-binding prodrug, was designed to improve the therapeutic index of doxorubicin.…”

“…In our previous work, we established the importance of Cav-1 and caveolae-mediated endocytosis for HSA uptake and consequently HSA-bound drugs. 7,12 In these studies, we have shown that drugs bound or conjugated to HSA have a higher uptake and subsequent cytotoxic effect on cells expressing relatively higher Cav-1 levels, nominating Cav-1 as a potential biomarker of this class of therapeutics. To confirm whether these previous observations would extend to molecules that would independently bind to albumin, we studied the cytotoxic effect of IPBA-Dox in PANC1 and MP2 cells with genetically depleted Cav-1 levels by shRNA.…”

“…Caveolin-1 (Cav-1) is the main structural component of caveolae and is crucial for caveolae-mediated endocytosis. Caveolae are small (50–100 nm) flask-shaped invaginations in the plasma membrane that are important for cholesterol homeostasis, nutrient uptake, and signal transduction. ,− Importantly, Cav-1 has been found to be upregulated in several cancer types including pancreatic adenocarcinomas, breast cancer, and nonsmall cell lung cancers, among others. − In addition, Cav-1 has been found to be associated with worse clinical outcomes in certain cancer types. − ,− Finally, previous work from our group showed that Cav-1 expression is crucial for the uptake of HSA and HSA-bound chemotherapies, thereby potentially serving as a biomarker for response to these treatments. ,, Recently, we and others demonstrated that Cav-1 may serve as a biomarker for response to albumin-bound or conjugated chemotherapy in multiple clinical cohorts. − …”

“…Human serum albumin (HSA) is the most abundant protein in plasma, with a relatively long half-life of 19 days in the circulation. HSA has been shown to improve the pharmacokinetic profile of drugs bound to it − and it has been well established that HSA naturally accumulates in tumors due to abnormal angiogenesis and leaky vasculature of solid tumors, which is known as the enhanced permeability and retention effect (EPR). − In addition to this form of tumor targeting, cancer cells can readily take up HSA via caveolae-mediated endocytosis. − Because of these properties, HSA is an interesting drug carrier candidate for the development of novel chemotherapeutic approaches to cancer treatment.…”

The mechanism of the anti-inflammatory effect of Oldenlandia diffusa on arthritis model rats: a quantitative proteomic and network pharmacologic study

“…CAV1 has been established as the principal structural protein of caveolae ( 33 ), one of the 3 members of the caveolin family ( 34 ). It is widely distributed in adipocytes, endothelial cells, and fibroblasts ( 35 ), and might play a role in the inflammatory response in RA ( 35 ).…”