Recently, DKK1 has garnered attention in tumor therapy due to promising clinical studies. Junshi Biosciences' JS015 injection, a humanized anti-DKK1 monoclonal antibody for advanced malignant solid tumors, received IND acceptance last year. Leap Therapeutics' Sirexatamab (DKN-01, formerly LY-2812176) is in phase II studies for liver and gastric cancer. BHQ-880, another DKK1 antibody, completed a phase II clinical trial for multiple myeloma in 2020.
As a classical Wnt signaling pathway antagonist, DKK1 acts as a serological marker for tumor diagnosis and prognosis, while also becoming a crucial target in tumor therapy. All in all, its multi-functions in multiple cancers offer potential for enhancing current treatment approaches.
Dickkopf-related protein 1 (DKK1) is a Wnt/β-catenin signaling pathway inhibitor belonging to the DKK family (Others include DKK2, DKK3, and DKK4). Encoded by the human DKK1 gene, it is a secreted glycoprotein with around 266 amino acids. DKK1's structure includes an N-terminal signaling sequence, two conserved cysteine-rich regions (Dkk_N and coadjunctional folding region), and an N-glycosylation site near the C-end [1-3].
The DKK1 peptide is localized in the endoplasmic reticulum and secreted extracellularly through the 20-30 amino acid signal sequence. Its cofilin folding region, with short β-stacks and disulfide bonds, interacts with Wnt receptors LRP5/LRP6 and membrane-penetrating proteins Kremen1/2, inducing endocytosis and inhibiting the Wnt signaling pathway (Figure 1) [1-3].
Figure 1. DKK1 structure [1]
DKK1 is primarily secreted by osteoblasts and osteocytes, and it is also expressed to a lesser extent in various tissues and cell types, such as placenta, skin, prostate, vascular endothelium, and kidney, among others. As a secreted glycoprotein, DKK1 acts as an antagonist of the Wnt/β-catenin signaling pathway by competitively binding to LRP5/6 receptors with Wnt proteins [3-6].
This regulation influences cell proliferation, differentiation, carcinogenesis, apoptosis, tumor cell invasion, and metastasis. Increasing evidence suggests that DKK1 exhibits diverse characteristics in tumorigenesis and development. Even in the same type of cells, it can demonstrate opposite regulatory effects due to different physiological environments, making its function relatively complex [3-6].
DKK1 is a well-known inhibitor of the Wnt/β-catenin signaling pathway, playing a vital role in regulating cellular processes and impacting tumor development. Recent studies indicate that DKK1 may not always act as an inhibitor, possibly due to β-catenin gene mutations [7-12].
Current research suggests that DKK1 negatively regulates the classical Wnt pathway through two mechanisms. Firstly, it competes with Frizzled-related proteins, hindering their binding to Wnt. Secondly, DKK1 binds to Wnt receptors LRP5/6 and co-receptors Kremen1/2 on the cell membrane, leading to endocytosis, effectively inhibiting Wnt signaling and halting abnormal target gene transcription [7-12].
Moreover, DKK1 is itself a target gene of the classical Wnt pathway, with its promoter region containing a β-catenin binding site. Some studies propose that transcriptionally generated DKK1 engages in negative feedback to suppress the expression of upstream genes, working alongside other factors in the signaling chain to maintain internal environment homeostasis (Figure 2) [7-12].
Figure 2. DKK1 negatively regulates Wnt/β-catenin signaling pathway [12]
DKK1 plays a crucial role in various diseases through the Wnt/β-catenin signaling pathway. In tumors, DKK1 has shown different expressions under various conditions.It acts as a pro-carcinogenic gene in multiple myeloma [11], hepatocellular carcinoma [12], hepatoblastoma/nephroblastoma [13], non-small cell lung cancer [14], head and neck cancer [15], esophageal cancer [16], pancreatic cancer [17], etc., while functioning as an oncogene in gastric cancer [18], bladder cancer [19], melanoma [20], and colorectal cancer [21].
DKK1 plays a significant role in multiple myeloma (MM) by promoting bone destruction. Inhibiting DKK1 has been shown to attenuate bone destruction. High DKK1 expression is associated with extensive bone destruction as it inhibits the differentiation of bone marrow stem cells into osteoblasts. Recent advances in targeting DKK1, including antibodies and vaccines, offer promising new treatments for MM [22].
Studies have found that anti-DKK1 vaccines trigger T cell responses and protect against MM in animal models. Combining DKK1 with MMSA-1 in a multi-epitope antigen vaccine enhances CD4+ and CD8+T cell immune responses, leading to improved inhibition of myeloma cells and bone destruction [22]. Targeting DKK1 may open up new avenues for multiple myeloma therapy.
DKK1 is strongly expressed in gastric cancer cells but weakly in normal gastric mucosa. High DKK1 expression is linked to advanced stages of gastric cancer, distant metastasis, lymphatic infiltration, and vascular invasion. Knockdown of DKK1 reduces the proliferation and invasion ability of gastric cancer cells, leading to lower survival rates in DKK1-positive gastric cancer patients. Elevated serum DKK1 levels and increased DKK1 expression in gastric cancer tissues could aid in diagnosing and predicting gastric cancer [23-25].
Sirexatamab (DKN-01), a targeted drug against DKK1, shows promise in clinical gastric cancer treatment. It reduces vascular proliferation, upregulates key cytokines IFNγ, IL-15 and IL-33, promotes tumor cell death, activates the Wnt pathway, reprograms MDSCs, and reduces their immunosuppressive activity (Figure 3) [23-25].
Figure 3. Sirexatamab (DKN-01) shows potential in the clinical treatment of gastric cancer [25]
Vasculogenic Mimicry (VM) is a blood vessel-like structure formed by tumor cells under specific conditions, facilitating blood transport and promoting tumor growth and vessel construction. Tumor cells involved in VM exhibit a higher propensity for bloodstream metastasis and show resistance to chemotherapy and anti-angiogenic treatments, resulting in a poor prognosis for patients. Interestingly, in colon cancer tissues where VM is present, DKK1 expression was found to be low [4, 26].
Moreover, when DKK1 was overexpressed in HCT116 cells, their ability to form tubular structures and VE-cadherin expression were significantly reduced. Additionally, DKK1 inhibited VM formation in transplanted tumor tissues from nude mice. Therefore, DKK1 overexpression appears to play a role in inhibiting VM formation in colorectal cancer [4, 26].
The role of DKK1 in breast cancer is multifaceted, potentially exerting both tumor-suppressive and tumor-promoting effects. On one hand, DKK1 has been implicated as an inhibitor of breast cancer, particularly in the context of bone metastasis, where it enhances osteoclast activity and inhibits breast cancer cell metastasis to bone. Therefore, elevated serum DKK1 levels can serve as a specific diagnostic indicator for breast cancer bone metastasis [27].
On the other hand, DKK1 has been shown to possess the ability to promote angiogenesis, breast cancer cell migration, and invasion. Activation of DKK1 via VEGFR2 can induce angiogenesis through the VEGFR2 signaling cascade, thereby increasing the invasive and angiogenic capacities of breast cancer cells [28-29].
In the noninvasive serology for pancreatic cancer detection, the expression levels of CA19-9, s-ULBP2, and DKK1 in serum were compared among patients with benign pancreatic disease, pancreatic cancer, and healthy individuals. The experimental findings revealed significantly elevated levels of serum CA19-9, s-ULBP2, and DKK1 in pancreatic cancer patients compared to the benign pancreatic disease group and healthy control group [30].
Logistic regression and ROC curve analysis indicated that CA19-9 exhibited the highest sensitivity, while DKK1 showed the highest specificity. The study concluded that a combination of these three tests can enhance the diagnostic accuracy of pancreatic cancer and evaluate the clinical treatment efficacy for pancreatic cancer management [30].
Based on the GEPIA database, DKK1 expression was found to be decreased in bladder cancer tissues compared to paraneoplastic tissues, and patients with high DKK1 expression had reduced overall survival compared to those with low DKK1 expression. ELISA analysis of serum DKK1 concentrations revealed significantly higher levels in bladder cancer patients compared to healthy individuals, and even higher levels in bladder cancer patients with lymph node metastases compared to those without metastases [19, 31].
Additionally, stage III + IV bladder cancer patients exhibited higher DKK1 concentrations than stage I + II patients. However, these experimental findings contradicted the results obtained from the database, possibly due to the different measurement objects (serum protein level vs. gene level in tissues) [19, 31]. Therefore, further validation is required to elucidate the specific role of DKK1 in bladder cancer development and explore its potential as a new therapeutic target.
DKK1 is associated with various diseases, besides its link to tumors. In a rat model of Parkinson's disease, DKK1 is induced in the ventral midbrain after 6-OHDA injury, and knockdown of DKK1 attenuates MPP+-induced apoptosis in PC12 cells and promotes β-catenin and p-Ser9-GSK-3β expression [32].
Moreover, DKK1 not only inhibits osteoblasts but also activates osteoclasts, leading to disrupted bone homeostasis and inhibition of bone formation. Studies suggest that DKK1 may be involved in the process of new bone formation, such as in Ankylosing Spondylitis (AS) [33].
Additionally, in periodontitis studies, down-regulation of DKK1 inhibits the pro-inflammatory cytokine IL-1β, IL-6, and IL-8 expression, and promotes the expression of the osteogenic marker BMP-2, OCN, and RunX2 mRNA expression as well as calcium nodule generation. This, in turn, promotes osteogenic differentiation of human periodontal stem cells (hPDLSCs), thereby inhibiting the development of periodontitis. Further study of the role of DKK1 in these diseases could help to discover new therapeutics and drugs [34-35].
Based on data from Pharmsnap (Table 1), ongoing clinical investigations are exploring drugs like BHQ-880 and Sirexatamab as DKK1 inhibitors for various tumors, including multiple myeloma. DKK1-loaded dendritic cell vaccines and JS015 monoclonal antibody also show promise. Notably, the phase 2a clinical trial of Sirexatamab in first-line treatment for advanced gastric cancer and gastroesophageal conjugate cancer demonstrated an impressive objective remission rate (ORR) of 68.2%, with an even higher ORR of 90% in patients with DKK1-overexpressing tumors [36].
Furthermore, other DKK1 inhibitors and modulators are in the preclinical or drug discovery stages for conditions such as hepatocellular carcinoma, ovarian carcinoma, endometrial carcinoma, prostate cancer, and immunoglobulin A nephropathy. Through targeted therapeutic approaches against DKK1 using different types of drugs like monoclonal antibodies, recombinant peptides, and small molecules, developing more effective treatments is expected, bringing new hope for combating tumors and autoimmune diseases.
Drugs Name | Target | Mechanism of Action | Indications | Highest drug development status (global) | Type of drug | Institutions |
---|---|---|---|---|---|---|
BHQ-880 | DKK1 | DKK1 inhibitor | multiple myeloma | Clinical Phase 2 | monoclonal antibody | Novartis AG; MorphoSys AG; Novartis Pharma AG |
Sirexatamab (DKN-01) | DKK1 | DKK1 inhibitor | Colorectal Cancer; Gastric Adenocarcinoma; Esophageal Cancer; Gastroesophageal Junction Cancer; Biliary Tract Tumors; Liver Cancer; Ovarian Cancer; Endometrial Cancer; Prostate Cancer; Gastric Cancer; Multiple Myeloma; Non-Small-Cell Lung Cancer; Sarcoma; Squamous Cell Carcinoma | Clinical Phase 2 | monoclonal antibody |
Leap Therapeutics, Inc.;Eli Lilly & Co. |
DKK1 loaded dendritic cell vaccine (Case Comprehensive Cancer Center) | DKK1 | immunostimulant |
Amyloidosis; Immunoglobulin a nephropathy; Monoclonal gammopathy of undetermined significance; multiple myeloma; negative combustion multiple myeloma |
Early clinical stage 1 | prophylactic vaccine | The Case Comprehensive Cancer Center |
JS015 | DKK1 | DKK1 inhibitor | advanced malignant solid tumor | Clinical application approval | monoclonal antibody | Shanghai Junshi Biosciences Co. |
DKK1-CAR-iNKT | DKK1 | / | neoplasms | preclinical | monoclonal antibody | Arovella Therapeutics Ltd. |
anti-DKK1 antibodies | DKK1 | DKK1 regulator | neoplasms | preclinical | biopharmaceutical |
Twist Bioscience Corp. |
APC-002 | DKK1 | DKK1 inhibitor | Esophageal cancer; stomach cancer | preclinical | biopharmaceutical | Aptacure Therapeutics Ltd. |
Recombinant human R-spondin 1 | DKK1 | DKK1 regulator | / | Clinical Phase 1 | recombinant peptide | / |
RN-564 | DKK1 | DKK1 inhibitor | / | Clinical Phase 1 | monoclonal antibody | / |
IIIC3 (Enzo Biochem, Inc.) | DKK1 | DKK1 inhibitor | / | drug discovery | small molecule chemotherapy | / |
Mab-B3 | DKK1 | DKK1 inhibitor | / | drug discovery | monoclonal antibody | / |
Table 1. DKK1 Clinical Trials for Drug Development
To fully support researchers and pharmaceutical companies in their research on DKK1 in cancers or other diseases, CUSABIO presents DKK1 active protein to support your research on the mechanism of DKK1 or its potential clinical value (click for the full list of DKK1 products: DKK1 proteins; DKK1 antibodies; DKK1 kits).
DKK1 protein
Recombinant Human Dickkopf-related protein 1(DKK1) (Active) (Code: CSB-MP006920HU(A4))
The purity was greater than 95% as determined by SDS-PAGE. (Tris-Glycine gel) Discontinuous SDS-PAGE (reduced) with 5% enrichment gel and 15% separation gel.
Immobilized Human DKK1 at 2 μg/mL can bind Anti-DKK1 recombinant antibody (CSB-RA006920MA1HU), the EC50 is 1.283-2.544 ng/mL.
References
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