This work was financially supported by the R&#38;D Plan of Guangdong Province (PR China) (2016A050503028).

All of the procedures including human blood collection were approved by the Sun Yat-Sen University Ethics Committee.
1. GPC3-S-Fab Design Strategy
<ol>
	<li>Design GPC3-S-Fab by linking a Fab of anti-GPC3 (humanized GC3313) with an anti-CD16 VHH14 (Figure 1).</li>
	<li>Synthesize and clone the VH-CH1-CD16-VHH and VL-CL into the pET26b and pET21a vectors as previously reported12.</li>
</ol>
<...

<ol>
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C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Camelid+Single-Domain+Antibodies+As+an+Alternative+to+Overcome+Challenges+Related+to+the+Prevention,+Detection,+and+Control+of+Neglected+Tropical+Diseases.">Camelid Single-Domain Antibodies As an Alternative to Overcome Challenges Related to the Prevention, Detection, and Control of Neglected Tropical Diseases.</a> Frontiers in Immunology. 8, 653 (2017).</li><li>Li, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+bispecific+antibody,+S-Fab,+induces+potent+cancer+cell+killing.">A novel bispecific antibody, S-Fab, induces potent cancer cell killing.</a> Journal of Immunotherapy. 38 (9), 350-356 (2015).</li><li>Li, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single-domain+antibody-linked+Fab+bispecific+antibody+Her2-S-Fab+has+potent+cytotoxicity+against+Her2-expressing+tumor+cells.">A single-domain antibody-linked Fab bispecific antibody Her2-S-Fab has potent cytotoxicity against Her2-expressing tumor cells.</a> AMB Express. 6 (1), 32 (2016).</li><li>Nakano, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-glypican+3+antibodies+cause+ADCC+against+human+hepatocellular+carcinoma+cells.">Anti-glypican 3 antibodies cause ADCC against human hepatocellular carcinoma cells.</a> Biochemical and Biophysical Research Communications. 378 (2), 279-284 (2009).</li><li>Behar, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+anti-FcgammaRIII+(CD16)+llama+single-domain+antibodies+that+activate+natural+killer+cells.">Isolation and characterization of anti-FcgammaRIII (CD16) llama single-domain antibodies that activate natural killer cells.</a> Protein Engineering, Design, and Selection. 21 (1), 1-10 (2008).</li><li>Baral, T. 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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glypicans:+proteoglycans+with+a+surprise.">Glypicans: proteoglycans with a surprise.</a> Journal of Clinical Investigation. 108 (4), 497-501 (2001).</li><li>Baumhoer, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glypican+3+expression+in+human+nonneoplastic,+preneoplastic,+and+neoplastic+tissues:+a+tissue+microarray+analysis+of+4,387+tissue+samples.">Glypican 3 expression in human nonneoplastic, preneoplastic, and neoplastic tissues: a tissue microarray analysis of 4,387 tissue samples.</a> American Journal of Clinical Pathology. 129 (6), 899-906 (2008).</li><li>Llovet, J. 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In this study, we present a strategy to construct a new format of bsAbs, GPC3-S-Fab, which can recruit NK cells targeting GPC3 positive tumor cells. The S-Fab is based on the natural Fab format by adding an anti-CD16 VHH11,12. Compared with the bsAbs containing Fc region, GPC3-S-Fab can easily be produced in the periplasm of bacteria on a large scale.
Using the expression and purification strategy described in the protocol, we obtained...

Monoclonal antibodies are now broadly used for cancer treatment1. Due to the flexibility of antibodies, various antibody-based formats have been actively explored. Compared with monoclonal antibodies, bsAbs have two different antigen binding modules, enabling them to recognize two different targets simultaneously and efficiently trigger the recruitment of immune effector cells to target and kill tumor cells2.
Current recombinant bsAb formats can be generally assigned to two classes: Fc-containing bsAbs and bsAbs without an Fc region. Compared with Fc-containing formats that are mostly produced in mammalian cells, bsAbs without an Fc region have the advantages of smaller sizes, are more readily produced in microorganism expression systems, and can penetrate tumor tissues more efficiently3.
bsAbs without an Fc region are commonly formed by linking individual binding moieties, such as single-chain variable fragments (scFvs) or Fabs3. Without the stabilizing domains, bsAbs based on scFv fragments often have compromised thermal stability, low solubility, or an increased potential for aggregation4,5. In contrast, Fab-based bsAbs are more stable due to the heterodimerization of the CH1 and CL in the native Fab moiety4,6.
Variable domain from heavy-chain-only antibodies (VHHs, also referred to as single domain antibodies) are the active antigen-binding fragment of natural heavy chain antibodies7. VHHs have the characteristics of high affinity, specificity of conventional IgGs8, low immunogenicity, and high yields in bacterial expression9. Compared with Fv fragments, VHHs have higher thermal stability10. Compared with Fab moieties, VHHs have smaller sizes due to the lack of CH1 and CL. Thus, S-Fab, the bsAb format obtained by linking the Fab with a single domain antibody, VHH, was designed and studied for its anti-tumor effects11,12.
In this study, the construction of GPC3-S-Fab by linking the Fab of hGC3313 with an anti-CD16a VHH14 was described. The GPC3-S-Fab can be efficiently produced by periplasmic expression in Escherichia coli (E. coli). Functional studies of GPC3-S-Fab suggested that GPC3-S-Fab is a promising strategy for liver cancer therapy. Thus, the advantages of GPC3-S-Fab over alternative techniques with applicable references to previous studies include easy production and purification, and more stable bsAbs.
Mammalian expression systems and prokaryotic expression systems have been used to express various formats of BsAbs. In contrast to mammalian expression systems, E. coli-based protein expression systems have many benefits, including high yields, low cost and labor-saving, the ease of genetic manipulations, and high transformation efficiency15. For bsAbs expression in E. coli, there are two basic strategies: expression in the cytoplasm and expression in the periplasm between the cytoplasm and outer cell membranes15. Compared to the reducing environment of cytoplasm, the periplasm is a more oxidizing environment, which promotes the correct folding and co-expression of proteins16. Correct folding plays a key role in solubility, stability and function generation of bsAbs. Therefore, a signal sequence pelB was added to the N-terminus of the S-Fab to direct secretion to the periplasm of E. coli17. To ensure correct folding, solubility, thermal stability, and conformational stability, reducing the complexity and the size of an antibody is frequently employed16. The S-Fab format consists of one Fab and one VHH, which is expressed very well in bacterial systems likely due to the simple structure and small size.
GPC3 was chosen in this GPC3-S-Fab bispecific antibody format. Glypican-3 (GPC3) is a member of the heparin sulfate (HS) proteoglycan family that is anchored to the cell surface through glycosylphosphatidylinositol (GPI)18. GPC3 is overexpressed in 70% of hepatocellular carcinoma (HCC) cases, which account for the majority of liver cancers19,20,21,22. Because GPC3 is rarely expressed in normal tissues, GPC3 has been proposed as a potential target for HCC. Multiple mouse mAbs have been produced against GPC3. However, only GC33 exhibited limited anti-tumor activity 22, and it failed to exhibit clinical efficacy in patients. In this study, GPC3-S-Fab was shown to be able to recruit NK cells to kill GPC3 tumor cells14.
To recruit NK cells, anti-CD16 VHH was used. CD16a is a low affinity IgG receptor, expressed mainly on natural killer (NK) cells, macrophages, monocytes and some subtypes of T cells. It is involved in antibody-dependent cell cytotoxicity (ADCC) by NK cells23. Human NK cells can be categorized into two types, CD56-CD16+ and CD56+CD16-. In contrast to CD56+CD16&#8722; NK cells, CD56-CD16+ NK cells can release higher levels of perforin and granzyme B and thus present a strong cytotoxicity24. Kupffer cells (KCs), expressing CD16a, are the resident macrophages in liver. Kupffer cells play an important role in the suppression of liver cancer25. Thus, bsAbs targeting CD16a may be a more promising strategy than engaging T cells against liver cancer.

<table>
	<tbody>
		<tr>
			<td>Shaking incubator</td>
			<td>Thermo Fisher</td>
			<td>MAXQ 4000</td>
			<td></td>
		</tr>
		<tr>
			<td>Shaking incubator</td>
			<td>Zhicheng</td>
			<td>ZWYR-D2402</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Cence</td>
			<td>GL-10MD</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Beckman coulter</td>
			<td>Avanti j-26S XPI</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>eppendorf</td>
			<td>5810R</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultraviolet spectrophotometer</td>
			<td>Thermo Fisher</td>
			<td>Nanodrop</td>
			<td></td>
		</tr>
		<tr>
			<td>Analytical polyacrylamide gel electrophoresis apparatus</td>
			<td>Mini-PROTEAN&#174; Tetra</td>
			<td>Bio-rad</td>
			<td></td>
		</tr>
		<tr>
			<td>Trans-blot apparatus</td>
			<td>Criterion</td>
			<td>Bio-rad</td>
			<td></td>
		</tr>
		<tr>
			<td>Imaging system</td>
			<td>Bio-rad</td>
			<td>chemidoc tm XRS+</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast Protein Liquid chromatogram</td>
			<td>GE Healthcare</td>
			<td>AKTA avant</td>
			<td></td>
		</tr>
		<tr>
			<td>GF column</td>
			<td>GE Healthcare</td>
			<td>28-9909-44 Superdex 200 Increase 10/300 GL</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Cytometer</td>
			<td>Beckman coulter</td>
			<td>FC500</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>eppendorf</td>
			<td>5702R</td>
			<td></td>
		</tr>
		<tr>
			<td>Envision plate reader</td>
			<td>TECAN</td>
			<td>Infinite F50</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti His-tag</td>
			<td>eBioscience</td>
			<td>14-6657-82</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Flag-tag</td>
			<td>Sigma</td>
			<td>F1804</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-human(H&#38;L)-488</td>
			<td>A11013</td>
			<td>Invitrogen</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse IgG HRP-linked antibody</td>
			<td>Cell Signaling</td>
			<td>7076S</td>
			<td></td>
		</tr>
		<tr>
			<td>Ni-NTA-Agarose</td>
			<td>Tribioscience</td>
			<td>TBS9202-100</td>
			<td></td>
		</tr>
		<tr>
			<td>IgG-CH1 affinity resin</td>
			<td>Thermo Fisher</td>
			<td>194320005</td>
			<td></td>
		</tr>
		<tr>
			<td>Ficoll-Plaque Plus</td>
			<td>GE Healthcare</td>
			<td>17-1440-03</td>
			<td></td>
		</tr>
		<tr>
			<td>NK cell enrichment kit</td>
			<td>Stemcell</td>
			<td>19055</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnet</td>
			<td>Stemcell</td>
			<td>18000</td>
			<td></td>
		</tr>
		<tr>
			<td>CCK8 kit</td>
			<td>Dojindo</td>
			<td>CK04</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibco</td>
			<td>C11995500CP</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI-1640</td>
			<td>Gibco</td>
			<td>C11875500CP</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Sigma</td>
			<td>F2442</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Gibco</td>
			<td>15050-057</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>Cell culture</td>
		</tr>
		<tr>
			<td>Standard marker</td>
			<td>Sigma Aldrich</td>
			<td>MWGF200</td>
			<td>Gel filtration</td>
		</tr>
		<tr>
			<td>Isopropyl-b-D-thio-galactopyranoside (IPTG)</td>
			<td>VWR chemicals</td>
			<td>VWRC0487-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Dialysis tubing</td>
			<td>Sigma Aldrich</td>
			<td>D0655-100FT</td>
			<td></td>
		</tr>
		<tr>
			<td>Knanamycine</td>
			<td>VWR</td>
			<td>VWRC0408-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Ampicillin</td>
			<td>VWR</td>
			<td>VWRC0339-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptone</td>
			<td>Thermo Fisher</td>
			<td>LP0042B</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract</td>
			<td>Thermo Fisher</td>
			<td>LP0021B</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sangon Biotech</td>
			<td>A100241</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma Aldrich</td>
			<td>T6791-1KG</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Sigma Aldrich</td>
			<td>V900106</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>aladdin</td>
			<td>A110752-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>aladdin</td>
			<td>P112134-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl</td>
			<td>Sigma Aldrich</td>
			<td>V900020</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>Sangon Biotech</td>
			<td>A505255-0250</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Phosphate, Monobasic Anhydrous (KH2PO4)</td>
			<td>VWR</td>
			<td>7778-77-0</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Phosphate, Dibasic, Anhydrous (Na2HPO4)</td>
			<td>VWR</td>
			<td>7558-79-4</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol</td>
			<td>VWR</td>
			<td>60-24-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenylmethyl Sulfonyl Fluoride (PMSF)</td>
			<td>VWR</td>
			<td>329-98-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysozyme</td>
			<td>Sigma Aldrich</td>
			<td>L6876-25G</td>
			<td></td>
		</tr>
		<tr>
			<td><a name="RANGE!A50">Coomassie Brilliant Blue R250</a></td>
			<td>VWR</td>
			<td>VWRC0472-50G</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Sangon Biotech</td>
			<td>A500922-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td>VWR</td>
			<td>VWRC0332-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma Aldrich</td>
			<td>V900122</td>
			<td></td>
		</tr>
		<tr>
			<td>100mm x 20mm plastic dish</td>
			<td>Corning</td>
			<td>430167</td>
			<td></td>
		</tr>
		<tr>
			<td>25cm2 flask</td>
			<td>Corning</td>
			<td>430639</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well cell culture cluster</td>
			<td>Corning</td>
			<td>3599</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sangon Biotech</td>
			<td>A610498-0005</td>
			<td></td>
		</tr>
		<tr>
			<td>CHO</td>
			<td>the Type Culture Collection of the Chinese Academy of Sciences</td>
			<td>GNHa 3</td>
			<td></td>
		</tr>
		<tr>
			<td>MHCC-97H</td>
			<td>the Type Culture Collection of the Chinese Academy of Sciences</td>
			<td>SCSP-528</td>
			<td></td>
		</tr>
		<tr>
			<td>HepG2</td>
			<td>the Type Culture Collection of the Chinese Academy of Sciences</td>
			<td>TCHu 72</td>
			<td></td>
		</tr>
		<tr>
			<td>Huh7</td>
			<td>the Type Culture Collection of the Chinese Academy of Sciences</td>
			<td>TCHu182</td>
			<td></td>
		</tr>
		<tr>
			<td>Hep3B</td>
			<td>the Type Culture Collection of the Chinese Academy of Sciences</td>
			<td>TCHu106</td>
			<td></td>
		</tr>
		<tr>
			<td>NK92</td>
			<td>ATCC</td>
			<td>CRL2408</td>
			<td></td>
		</tr>
	</tbody>
</table>

a gpc3-targeting bispecific antibody, gpc3-s-fab, with potent cytotoxicity

This protocol describes the construction and functional studies of a bispecific antibody (bsAb), GPC3-S-Fab. bsAbs can recognize two different epitopes through their two different arms. bsAbs have been actively studied for their ability to directly recruit immune cells to kill tumor cells. Currently, the majority of bsAbs are produced in the form of recombinant proteins, either as Fc-containing bsAbs or as smaller bsAb derivatives without the Fc region. In this study, GPC3-S-Fab, an antibody fragment (Fab) based bispecific antibody, was designed by linking the Fab of anti-GPC3 antibody GC33 with an anti-CD16 single domain antibody. The GPC3-S-Fab can be expressed in Escherichia coli and purified by two affinity chromatographies. The purified GPC3-S-Fab can specifically bind to and kill GPC3 positive liver cancer cells by recruiting natural killer cells, suggesting a potential application of GPC3-S-Fab in liver cancer therapy.

GPC3-S-Fab purification
GPC3-S-Fab was purified from E. coli by a two-step affinity purification, first with Ni-NTA-agarose, followed by IgG-CH1 affinity purification. After the two-step affinity purification, GPC3-S-Fab was purified to homogeneity with the two chains close to 1:1 (Figure 2A). The presence of both VH-CH1-CD16 VHH and VL-CL polypeptides can be identified by ...

Watch this Scientific Journal Video about A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity at JoVE.com

A GPC3-targeting Bispecific Antibody, GPC3-S-Fab, with Potent Cytotoxicity

Here, we present a protocol to produce a bispecific antibody GPC3-S-Fab in Escherichia coli. The purified GPC3-S-Fab has potent cytotoxicity against GPC3 positive liver cancer cells.

This protocol describes the construction and functional studies of a bispecific antibody (bsAb), GPC3-S-Fab. bsAbs can recognize two different epitopes ...

This method can help answer key questions in the bispecific antibody field, such as how to produce a bispecific antibody in bacteria and determine the function of the purified antibody. The main advantage of this technique is that GPC3-S-Fab can be easily produced and purified from E.coli. To prepare the periplasmic fraction, first centrifuge the cell suspension at 4, 000 g for 30 minutes at four degrees Celsius.Then, expel the medium, and weigh the cells. After centrifugation, dissolve the cell pellet in four milliliters of ice-cold sucrose solution for each gram of cells. Incubate the cell suspension on ice for 15 minutes.After 15 minutes, centrifuge the cell suspension at 8, 500 g for 20 minutes at four degrees Celsius. Then, pipette out the supernatant containing the sucrose fraction, and store it on ice. Resuspend the cell pellet in ice-cold mixture of five-millimolar magnesium chloride and one-millimolar PMSF.Then, add 40 microliters of 15 milligrams per milliliter of the lysosome stock to the cell suspension. After adding the lysosome stock, leave the cell suspension on ice for 30 minutes. After the incubation period is over, combine the sucrose and the periplasmic fractions.Then, centrifuge the sucrose-periplasmic fraction at 30, 000 g for 30 minutes at four degrees Celsius. After centrifugation is over, transfer the supernatant in a 50-milliliter conical tube on ice. Next, mix and resuspend one milliliter of nickel-NTA agarose with the supernatant to obtain a homogeneous suspension, then one milliliter of nickel-NTA agarose to a fresh 15-milliliter conical tube.To the agarose, add 10 column volumes of the equilibration buffer. Then, centrifuge the agarose at 400 g for five minutes. Post-centrifugation, carefully remove the supernatant, and add the nickel-NTA agarose to the sucrose-periplasmic fraction.Then, rock the sucrose-periplasmic fraction-containing tube at four degrees Celsius for two hours. Again, centrifuge the mixture. Then, carefully remove the supernatant to a fresh ice-cold tube since this is the unbound fraction.After the supernatant is transferred, add the nickel-NTA agarose in the gravity column. Then, add three column volumes of elution buffer to the column. Next, collect the eluate as elution fractions one, two, three, and four, respectively.Dilute and seed 5, 000 cells in 100 microliters in each well of a 96-well plate. Incubate the plate at 37 degrees Celsius for six to eight hours for attachment. To prepare the PBMCs, first dilute the freshly prepared blood with an equal volume of phosphate-buffered saline in a 50-milliliter conical tube.Pipette 15 milliliters of lymphocyte separation medium in a fresh 50-milliliter conical tube. Next, carefully transfer the diluted blood along the walls of the tube to the lymphocyte separation medium. Centrifuge the cells at 400 g for 35 minutes at room temperature with the brakes off.Post-centrifugation, carefully draw the upper plasma layer out. Then, pipette the white blood layer containing the PBMCs. Dilute these PBMCs obtained with double the volume of phosphate-buffered saline with 2%fetal bovine serum.Then, centrifuge the PBMC suspension. Wash the cell pellet with phosphate-buffered saline containing 2%fetal bovine serum, and again centrifuge. After centrifugation, count the cell number.To prepare the natural killer cells, reconstitute the PBMCs in phosphate-buffered saline with 2%fetal bovine saline. Then, transfer the mixture in a polystyrene round-bottom tube. Add 50 microliters per milliliter of natural killer cell enrichment cocktail to the PBMC mixture.Mix the contents, and leave the tube for 10 minutes. Next, resuspend and mix the magnetic particles present in the enrichment cocktail by pipetting multiple times, such that the particles are uniformly suspended. Then, add 100 microliters per milliliter of magnetic particles to the cell suspension.Mix the cell suspension magnetic particles, and incubate at room temperature for five minutes. After five minutes, add 2.5 milliliters of phosphate-buffered saline with 2%fetal bovine serum to the cell suspension. Gently pipette two to three times to mix the cells in the tube.Place the tube on the magnet, and let the magnetic beads settle down for 2.5 minutes at room temperature. Then, in one stroke of action, invert the tube, and pour the enriched cell suspension in a new tube. Again, count the number of cells.Once the counting is over, dilute the natural killer cells in the culture medium. Then, add 100 microliters of the cell suspension to the tumor cells plated in a 96-well plate. To set up the cytotoxicity assays, add 10 microliters of varying concentrations of GPC3-S-Fab antibody to the 96-well plate.Then, incubate the plate at 37 degrees Celsius for 72 hours. After the designated incubation time, aspirate the medium. Then, add 100 microliters of DMEM medium containing 10 microliters of CCK reagent in each well of the 96-well plate.Again, incubate the plate at 37 degrees Celsius. Post-incubation, read the plate at 450 nanometers every consecutive hour until four hours after the addition of the CCK8 reagent. The GPC3-S-Fab antibody is purified using a two-step affinity purification.Here, the two panels show that the antibody is purified using the nickel-NTA agarose and the IgG-CH1 affinity purification columns, respectively. Next, the binding affinity of the GPC3-S-Fab antibody is evaluated using GPC3-positive and negative cancer cell lines. The GPC3-S-Fab binds to all the GPC3-positive cells, such as Hep3B, Huh7, Hep2G, and CHO/GPC3.Interestingly, no or minimal binding is observed when GPC3-negative cells, such as MHCC-97H and CHO, are used. The cytotoxicity of the GPC3-S-Fab is also studied in the presence of the tumor cells incubated with fresh natural killer cells. The antibody GPC3-S-Fab elicits strong cytotoxicity against HepG2, Hep3B, and Huh7 seven cells in a dose-dependent manner in the presence of the natural killer cells.However, no such cytotoxicity is observed in the absence of the natural killer cells on the MHCC-97H cells. Once mastered, this technique can be done in six hours, if it is performed properly. While attempting this procedure, it's important to remember to keep the steps on ice.Following this procedure, other methods like xenograft modeling can be performed in order to answer additional questions, like in tumor effect in vivo. After its development, this technique paved the way for researchers in the field of bispecific antibody to explore antitumor effects in vitro. After watching this video, you should have a good understanding of how to produce a functional bispecific antibody targeting the tumor cells, especially the isolation of the NK cells.

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Cancer Research

8.5K vistas.  Sun Yat-Sen University. This method can help answer key questions in the bispecific antibody field, such as how to produce a bispecific antibody in bacteria and determine the function of the purified antibody. The main advantage of this technique is that GPC3-S-Fab can be easily produced and purified from E.coli. To prepare the periplasmic fraction, first centrifuge the cell suspension at 4, 000 g for 30 minutes at four degrees Celsius.Then, expel the medium, and weigh the cells. After centrifugation, dissolv...