Cancer biomarkers are critical tools in research and drug development, guiding treatment decisions and enhancing the success of new therapies of AKT1 antibodies. They are classified as either disease-related biomarkers, which assist with risk assessment, diagnosis, staging, and outcome prediction, or drug-related biomarkers, which inform treatment response and prognosis. By identifying patients most likely to benefit from specific therapies and by monitoring treatment efficacy and side effects, biomarkers support the advancement of personalized medicine. Ideal biomarkers are easily detectable, reproducible, cost-effective, and clinically meaningful in improving patient outcomes.
One of the key signaling pathways in cancer is the phosphoinositide 3-kinase (PI3K) pathway, also known as the AKT/mTOR pathway, which controls cell growth, proliferation, and metabolism. Aberrant activation of this pathway leads to genetic alterations, including loss of the tumor suppressor PTEN and, less frequently, gain-of-function mutations in PIK3CA and AKT1.
Targeting this pathway has led to the development of several cancer biomarkers, including AKT1 antibodies, which represent a novel class of therapeutic and diagnostic tools.
AKT1: structure, function, and oncogenic role
AKT, also known as protein kinase B, is a serine/threonine kinase first identified as an oncogene in 1987. It exists in three isoforms: AKT1, AKT2, and AKT3. Activation of AKT is initiated by the upstream signaling molecule phosphoinositide 3-kinase (PI3K), which generates phosphatidylinositol-3,4,5-trisphosphate (PIP3) to trigger AKT activation. The tumor suppressor PTEN negatively regulates this pathway by converting PIP3 back to phosphatidylinositol-4,5-bisphosphate (PIP2), thereby inhibiting AKT signaling.
The AKT1 E17K mutation is the most common oncogenic alteration of AKT1 in human cancers and has been associated with increased sensitivity to AKT inhibitor therapies. In breast cancer, the AKT1 (E17K) mutation is present in approximately 6.3% of cases, occurring more frequently in lower-grade tumors and potentially acting as a primary driver in a subset of patients.
In contrast, a variety of rarer somatic AKT1 mutations have been identified, primarily in advanced cancers. However, their biological significance and therapeutic implications remain poorly understood, and current data are insufficient to inform clinical management.
AKT1 as a therapeutic target
AKT is an essential tool in cancer, making the PI3K/AKT pathway an early focus for targeted therapy development. Targeting the PI3K/AKT pathway is a strategic approach in disease treatment, but traditional AKT inhibitors face challenges like resistance and off-target effects. More precise strategies, such as targeting specific AKT isoforms or using mutant-selective inhibitors, may offer improved effectiveness and safety. Additionally, ongoing efforts aim to identify reliable biomarkers that can better predict which patients will benefit from AKT-targeted therapies.
Researchers have also developed nanobodies that specifically target the AKT1 or AKT2 isoforms, allowing for more precise investigation of their individual functions. Some of these nanobodies can block the interaction between AKT and PIP3, a critical step in AKT activation. These tools represent a significant advance in studying isoform-specific signaling within the AKT pathway.
To study AKT isoform-specific expression and activation, researchers validated antibodies using HCT116 colon cancer cells with targeted knockouts of AKT1 and AKT2. The AKT1- and AKT2-specific antibodies, including those targeting their phosphorylated forms, showed high specificity without cross-reactivity between isoforms. Additionally, pan-AKT and phospho-AKT antibodies recognized both isoforms, with AKT1 being the main contributor to hydrophobic domain phosphorylation at Ser473 in these cells.
Development and types of AKT1 antibodies
AKT1 antibodies are generated by immunizing host animals (such as rabbits or mice) with peptides corresponding to unique regions of the AKT1 protein. The resulting antibodies can be monoclonal or polyclonal, each offering distinct advantages in specificity and sensitivity. Monoclonal antibodies bind to the single epitope of the antigen while polyclonal antibodies bind to the multiple epitopes in an antigen.
For example, Anti-AKT1 antibody is a rabbit polyclonal antibody helpful in western blotting, chromatin immunoprecipitation, and immunohistochemistry.
AKT antibodies can be either phosphorylated or non-phosphorylated. In a study, researchers developed TAT-tagged AKT1 antibody to test whether this peptide enables efficient delivery into human cells, producing both phosphorylated and unphosphorylated variants. These AKT1 proteins, expressed in E. coli, were purified using affinity, size exclusion, and anion exchange chromatography, and phosphorylation at Thr308 was confirmed by western blot and liquid chromatography-mass spectrometry (LC-MS)/MS. The TAT-tagged and untagged phosphorylated AKT1 variants showed equivalent levels of Thr308 phosphorylation, with no detectable phosphorylation at Ser473.
Future perspectives
Advances in technology and tumor biology are expanding the use of cancer biomarkers diagnosis, prognosis, and treatment, offering promising benefits for both patient care and healthcare systems.
Although AKT1 antibodies show considerable potential, they also present certain limitations. Therefore, rigorous validation and standardization of antibody-based assays are essential. For an AKT1 immunohistochemistry (IHC) test to be clinically viable as a biomarker, standardized protocols must be established to ensure reproducibility across laboratories. This includes defining scoring systems, establishing positive controls, and setting cut-off values for high AKT1 activation.
