Tag Archives: cancer peptide

cancer-peptide

New Drug candidates: Neoepitopes as cancer immunotherapy targets

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Cancer is a patient-specific disease, where no two tumors are alike. Neoepitopes are very frequent in all cancers. Amino acid substitutions can yield neoantigens that are detected by the immune system. So neoantigens have been used for therapeutic purposes such as identifying cancer variant peptides for diagnosis and treatment.

The neuropeptides have the following characteristics.

1. The 9-mer peptides are the most common among the high-binding neoantigens.

2. The neuropeptides have a hydropathy nature. The amino acid distributions, at all positions in neoepitopes of all lengths, contain more hydrophobic residues than the wild-type sequences.

3. Only a minority of predicted neoepitopes elicit protective tumor immunity. Peptide binding to a Human leukocyte antigen (HLA) molecule is a requirement for raising adaptive immunity.

How should we immunize against neoepitopes?

Since neoantigens are small peptides harboring tumor mutations, immunization with them usually needs strong immunostimulatory agents to produce an effective immune response.

Peptides as vaccines may not be able to stimulate the immune system powerfully enough on their own. Therefore, it is usually required to use an adjuvant in combination to elicit an effective immune response.

However, the MAPs-4 system, in which four copies of the same peptide epitope are synthesized on a lysine-based core, does not require a carrier protein, as the dense packing of multiple copies of an epitope in combination with a high-molar ratio produces a robust immunological response.

Accurate identification of neoepitopes and their subsequent use in cancer therapy is still in its nascent stages. With recent advances in Mass Spectrometry, faster and more precise identification of all expressed neoepitopes may be possible soon.


Neoepitopes as cancer immunotherapy targets: key challenges and opportunities

Pioneering Tumor Targeting and Imaging: Conjugated Synthetic Peptides

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The folate receptor alpha (FRα) is highly expressed in ovarian cancer and not in normal tissues. An FRα binding peptide C7 (Met-His-Thr-Ala-Pro-Gly-Trp-Gly-Tyr-Arg-Leu-Ser, MHTAPGWGYRLS)  was found to bind to FRα expressing cells. This tumor-targeting peptide was proved by both phage homing experiment and fluorescence imaging.

Tumor Targeting of Conjugated Synthetic Peptides
1. The FITC-conjugated peptide FITC-MHTAPGWGYRLS was dissolved in PBS.
2. The peptide was injected intravenously into a tumor-bearing nude mouse.
3. After 2 h, the tumor and other organ tissues were harvested and analyzed using a fluorescence imaging system.

Cell internalization of Synthesized Peptide
1. Cells were seeded in 24 well plates containing coverslips and incubated for 24 hours in a medium with FBS.
2. FITC conjugated peptide was incubated with the cells for 4 hours at 37 °C.
3. The cells were washed once with PBS and fixed in 4% paraformaldehyde.
4. Cells were washed three times with PBS and stained with DAPI for 20 min at room temperature.
5. Internalized fluorescent signals were imaged with a confocal microscope.

This tumor-specific peptide could be a potent and selective ligand for FRα. It has a great potential for the delivery of cancer therapeutics or imaging agents to express tumors.

Reference: Scientific Reports, volume 8, Article number: 8426 (2018)

tumor targeting peptides

tumor targeting peptides

Peptide Antigens from Tumor Cells Pave the Way for Innovative Cancer Vaccines

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Check the cancer peptide database for a list of tumor peptides.

Tumor antigens can be classified into two categories based on their expression pattern: tumor-specific antigens (TSA) and tumor-associated antigens (TAA).

Targeting tumor-associated antigens (TAAs) is a promising approach for cancer immunotherapy. Neoantigens are tumor-specific antigens originating from somatic mutations in cancer cells but not healthy tissues. So the TAAs are considered as ideal targets for novel immunotherapies. Antigens of three classes can induce tumor-specific T-cell responses.

1. Antigens derived from viral proteins: Viral proteins are produced inside the tumor cells. So the antigenic peptides can be detected by T cells.

2. Antigens derived from point mutations: Many CTL isolated from the tumors were found to recognize antigens that arise from point mutations in ubiquitously expressed genes. These mutations are passenger mutations, and the corresponding antigenic peptides are unique to the tumors in which they were identified.

3. Antigens encoded by cancer-germline genes: Cancer-germline genes are expressed in many cancer types and not in normal tissues except germline and trophoblastic cells. The tumor-specific pattern of expression results from the genome-wide demethylation in male germ cells.

A large number of antigenic peptides recognized by antitumor CTL have been identified. Candidate peptides can be synthesized and tested for HLA binding in vitro. The elution of antigenic peptides from MHC class I molecules immunopurified from the surface of tumor cells can be used to identify the antigens. TAAs can be targeted using peptide vaccines or by cellular approaches. The delivery of new peptide drugs might show great promise for future therapies.

Peptide Antigens

Tumor-associated peptide antigens

LifeTein can customize a discovery and development path to fit your exact needs for peptide synthesis.

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How BIRD-2 Peptide Takes Down B-Cell Lymphoma?

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The anti-apoptotic factor Bcl-2 is over-expressed in B-cell lymphoma cells as their primary survival mechanism by binding to IP3R2 on the endoplasmic reticulum (ER).  In this study, a cell-penetrating version of the BIRD-2 peptide (Bcl-2/IP3R Disrupter-2 peptide with a TAT sequence) made by LifeTein was used to break up the complex formed by Bcl-2 and IP3R2 in human diffuse large B-cell lymphoma (DLBCL) cells. Ca2+ signaling-related events are suggested to be the killing mechanism of BIRD-2 peptide on DLBCL cells.

BIRD-2, a peptide that explicitly disrupts the Bcl2/IP3R complex, was utilized to further verify the mitochondrial Ca2+ regulatory mechanism via the Bmal1-Bcl2/IP3R signaling pathway. It was found that BIRD-2 aggravated mitochondrial Ca2+ overload and apoptosis in vitro.

Purchase BIRD-2 peptide now. Click here.

BIRD-2 peptide (sequence: RKKRRQRRRGGNVYTEIKCNSLLPLAAIVRV) was purchased from LifeTein (South Plainfield, NJ, USA) with a purity of >85%.

Bird-2 Peptides & B-Cell Lymphoma

Reference:

BIRD-2 peptide (LifeTein, USA), specifically disrupting the Bcl2/IP3R complex, was used in HGHP-treated H9c2 cells for 12 h (20 μM)

Inhibiting Bcl-2 via its BH4 domain in DLBCL cancers to provoke pro-apoptotic Ca2+ signaling

BIRD-2, a BH4-domain-targeting peptide of Bcl-2, provokes Bax/Bak-independent cell death in B-cell cancers through mitochondrial Ca2+-dependent mPTP opening

Look Who’s Talking

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Intraspecies pheromone signaling regulated by proteases is critical for fungi procreation.  The fungal aspartyl protease Bar1 was shown to have unique substrate specificity of important implications in fungal evolution.  LifeTein synthesized substrate peptides of Bar1, dual-tagged with DABCYL and EDANS, from the sequence of α pheromone, the native target of Bar1. Referred to as internally quenched or IQ peptides, they were used in fluorescence resonance energy transfer (FRET) assays to study the enzyme kinetics of Bar1.

LifeTein’s Internally Quenched Peptides

mBio 6(6):e01604-15. doi:10.1128/mBio.01604-15. Evolutionary selection on barrier activity: Bar1 is an aspartyl protease with novel substrate specificity.

Peptide Applications

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Peptides can be used in a wide variety of research applications:

Anti-microbial Peptides

81 oligopeptides were synthesized by LifeTein and tested for inhibition of Enterococcus faecalis V583. Three peptides were found to inhibit V583. The peptide (NH2-VAVLVLGA-COOH) possessed activity in picomolar concentrations, being >10^6 -fold more active than the only other two and showing inhibitory activity. Pheromone killing of multidrug-resistant Enterococcus faecalis V583 by native commensal strains, PNAS, 2015 The fungal pathogen causes the skin disease for amphibians. Use of a potent antibiotic cocktail dramatically reduced culturable skin bacteria within 48 h. The synthetic peptides by LifeTein were used to reduce the skin bacteria. SSkin bacteria provide early protection for newly metamorphosed southern leopard frogs (Rana sphenocephala) against the frog-killing fungus, Batrachochytrium dendrobatidis, Biological Conservation, 2015

Anti-inflammatory Peptides

Anti-inflammatory peptides were isolated from alcalase hydrolysates out of tuna cooking juice by-product. Synthetic peptides from LifeTein were used to confirm the inhibitory anti-inflammatory activity. The amino acid sequences of the two anti-inflammatory peptides isolated from AH hydrolysates were Pro-Arg-Arg-Thr-Arg-Met-Met-Asn-Gly-Gly-Arg (1543.8 Da) and Met-Gly-Pro-Ala-Met-Met-Arg-Thr-Met-Pro-Gly (1211.5 Da).

Epitope Mapping

Peptide scanning involves the chemical synthesis of overlapping peptides covering the antigen sequence targeted by the investigated antibodies. Peptide truncations are used to further narrow down the epitope sequence and mutagenesis of each amino acid such as alanine substitution can also indicate the binding affinity. Cross-reactive epitopes were found in Borrelia burgdorferi p66. Cross-reactive epitopes in Borrelia burgdorferi p66, Clinical and Vaccine Immunology, 2015

Cell Penetrating Peptides and Scrambled Peptides

The CD81 peptides tagged with cell penetrating peptide RRRRRRR were used for the binding assay. The synthetic peptides from LifeTein were used to investigate the role of CD81 in the regulation of defense mechanisms against microbial infections. The scrambled peptides, RRRRRRR- CCGIRNSSVY, were used as the negative control for the study. CD81 Controls Immunity to Listeria Infection through Rac-Dependent Inhibition of Proinflammatory Mediator Release and Activation of Cytotoxic T Cells, The Journal of Immunology, 2015

Receptor Binding Study

His-tagged GLP-1 (7-36), glucagon, and gastric inhibitory polypeptides (GIP) by LifeTein were used to study GLP-1 receptor signaling regulation. The GLP-1 peptides bind specifically with lipids but not that of exendin 4.The His-Tagged GLP-1 were used for the binding reaction. The free peptide was captured by Cu++-NTA resin. The results indicated that His-tagged GLP-1 peptide binds to OEA in a dose-dependent and saturable way. Modulation of Glucagon-like Peptide (GLP)-1 Potency by Endocannabinoid-like Lipids Represents A Novel Mode of Regulating GLP-1 Receptor Signaling. Journal of Biological Chemistry, 2015

Antibody Blocking Peptides

Peptides can be used as blocking peptides for the competition assay. The excess of blocking peptides (20:1 peptide: antibody ratio) from LifeTein were mixed with antibodies. The antibody was neutralized in this way by incubating with an excess of peptide that corresponds to the epitope recognized by the antibody. The neutralized antibody is then used side-by-side with the antibody alone, and the results are compared. Whole Exome Sequencing Reveals ZNF408 as a New Gene Associated With Autosomal Recessive Retinitis Pigmentosa with Vitreal Alterations, Human Molecular Genetics, 2015

Protein-Protein Interactions

The B-cell lymphoma 2 (Bcl-2) peptides were biotinylated at N terminus for the protein-protein interactions. The biotin-BH4-Bcl-XL peptide and the scrambled peptide were immobilized on different channels of a streptavidin-coated sensor chip. Studies showed that Bcl-XL bound to the central domain of RyR3 via its BH4 domain. Further analysis of a mutated peptide at a specific site Lys87 showed a reduced binding affinity. These data suggest that BH4 domain and its specific site of Lys87 contributes to the interaction. Ryanodine receptors are targeted by anti-apoptotic Bcl-XL involving its BH4 domain and Lys87 from its BH3 domain, Nature Scientific Reports, 2015

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