Monitoring the Crosstalk Between the Estrogen Receptor and Human Epidermal Growth Factor Receptor 2 with PET

Estrone-Conjugated PEGylated Liposome Co-Loaded Paclitaxel and Carboplatin Improve Anti-Tumor Efficacy in Ovarian Cancer and Reduce Acute Toxicity of Chemo-Drugs

Purpose

Ovarian cancer is the most lethal gynecologic malignancy. The combination of paclitaxel (PTX) and carboplatin (CBP) is the first-line remedy for clinical ovarian cancer. However, due to the limitations of adverse reaction and lacking of targeting ability, the chemotherapy of ovarian cancer is still poorly effective. Here, a novel estrone (ES)-conjugated PEGylated liposome co-loaded PTX and CBP (ES-PEG-Lip-PTX/CBP) was designed for overcoming the above disadvantages.

Methods

ES-PEG-Lip-PTX/CBP was prepared by film hydration method and could recognize estrogen receptor (ER) over-expressing on the surface of SKOV-3 cells. The characterizations, stability and in vitro release of ES-PEG-Lip-PTX/CBP were studied. In vitro cellular uptake and its mechanism were observed by fluorescence microscope. In vivo targeting effect in tumor-bearing mice was determined. Pharmacokinetics and biodistribution were studied in ICR mice. In vitro cytotoxicity and in vivo anti-tumor efficacy were evaluated on SKOV-3 cells and tumor-bearing mice, respectively. Finally, the acute toxicity in ICR mice was explored for assessing the preliminary safety of ES-PEG-Lip-PTX/CBP.

Results

Our results showed that ES-PEG-Lip-PTX/CBP was spherical shape without aggregation. ES-PEG-Lip-PTX/CBP exhibited the optimum targeting effect on uptake in vitro and in vivo. The pharmacokinetics demonstrated ES-PEG-Lip-PTX/CBP had improved the pharmacokinetic behavior. In vitro cytotoxicity showed that ES-PEG-Lip-PTX/CBP maximally inhibited SKOV-3 cell proliferation and its IC₅₀ values was 1.6 times lower than that of non-ES conjugated liposomes at 72 h. The in vivo anti-tumor efficacy study demonstrated that ES-PEG-Lip-PTX/CBP could lead strong SKOV-3 tumor growth suppression with a tumor volume inhibitory rate of 81.8%. Meanwhile, acute toxicity studies confirmed that ES-PEG-Lip-PTX/CBP significantly reduced the toxicity of the chemo drugs.

Conclusion

ES-PEG-Lip-PTX/CBP was successfully prepared with an optimal physicochemical and ER targeting property. The data of pharmacokinetics, anti-tumor efficacy and safety study indicated that ES-PEG-Lip-PTX/CBP could become a promising therapeutic formulation for human ovarian cancer in the future clinic.

PET Imaging of Estrogen Receptors Using 18F-Based Radioligands

In vivo molecular imaging of estrogen receptor alpha (ER) can be performed via positron emission tomography (PET) using ER-specific radioligands, such as 16α-[¹⁸F]fluoro-17β-estradiol (¹⁸F-FES). ¹⁸F-FES is a radiopharmaceutical recently approved by the United States Food and Drug Administration for use with PET imaging to detect ER+ lesions in patients with recurrent or metastatic breast cancer as an adjunct to biopsy. ¹⁸F-FES PET imaging has been used in clinical studies and preclinical research to assess whole-body ER protein expression and ligand binding function across multiple metastatic sites, to demonstrate inter-tumoral and temporal heterogeneity of ER expression, to quantify the pharmacodynamic effects of ER antagonist treatment, and to predict endocrine therapy response. ¹⁸F-FES PET has also been studied for imaging ER in endometrial and ovarian cancer. This chapter details the experimental protocol for ¹⁸F-FES PET imaging of ER in preclinical tumor xenograft models. Consistent adherence to key methodologic details will facilitate obtaining meaningful and reproducible ¹⁸F-FES PET preclinical imaging results, which could yield additional insight for clinical trials regarding imaging biomarkers and oncologic therapy.