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.

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 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.

Tumor-associated peptide antigens

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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.

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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

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.

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