Thread by @freddyeescorcia

Our lab’s inaugural manuscript is out (PMID: 31424293)!!! First #tweetorial (1/n) #chemtwitter #radonc #academicchatter #newPI #sciencetwitter #livercancer
tinyurl.com/y3rh7hq4

We have been exploring molecules that can specifically bind to liver cancer to improve upon existing modalities for diagnosis and surveillance. 2/n

So, why liver cancer? About 800,000 people are diagnosed with liver cancer worldwide, with as many people dying from the disease annually. In the U.S., incidence and mortality appear to be increasing. 3/n

Given that hepatocellular carcinoma (HCC) is the most common type of liver cancer, we wanted to apply lab expertise in chemistry, engineering, radiation, and oncology to develop HCC-selective imaging agents. 4/n

Glypican-3 (GPC3) is proteoglycan that is overexpressed in HCC that has been explored as a diagnostic and therapeutic target. Several groups have developed antibodies, peptides and vaccines to GPC3. 5/n

Since we develop agents for positron emission tomography (PET) imaging, we were especially interested in peptides that have been published to see if we could engineer imaging agents from these and, perhaps, improve upon their in vivo performance. 6/n

We identified TJ12P1 and L5 as the most promising (IPA is a derivative of TJ12P1), and synthesized variants with and without a fluorescent label for in vitro binding assessment with the goal of later optimization/mutimerization. (lower Kd=better target binding) 7/n

These variants were then tested in cell-based (flow cytometry) and cell-free (bio-layer interferometry) binding assays. Below are the results for peptide TJ12P1. (A431: GPC3-, G1=A431 engineered to be GPC3+; HepG2=GPC3+ liver ca line). 8/n

We were surprised to find that neither peptide bound to GPC3+ cells, and the control peptides (same amino acids, but arranged in diff order) bound “better.” 9/n

All associations appeared to be non-specific. Bakshinejab et al highlighted common features of "target unrelated peptides (TUPs)," namely hydrophobicity. Both TJ1 and L5 were VERY difficult to get into solution.
tinyurl.com/y29eykj4
10/n

Unlike prior published work, we used otherwise isogenic cell lines AND cell-free assays to better define the specificity of peptide-target associations. 11/n

While disappointing, we wanted to share our findings with the greater community because there are several groups building off the initial TJ12P1 and L5 peptide work who might be pursuing artifact as opposed to specific binding to the GPC3 target. 11/n

Lots of folks to thank especially former lab member Rose Berman @roseb_rklog, the @theNHLBI biophysics core, as well as the IPDC. Of course, @theNCI and @NCICCR_MIP and the #CIDP that is helping this #newpi get off the ground. ccr.cancer.gov/training/clini…