ROR1 on the Radar: Exploring its Potential as a Biomarker and Therapeutic Target in Cancer

What is ROR1？

ROR1 (Receptor Tyrosine Kinase-like Orphan Receptor 1) is a membrane-bound receptor protein categorized within the family of tyrosine kinase receptors. It holds a significant role in both embryonic development and specific tumor formations. Initially classified as an orphan receptor due to incomplete comprehension of its function and ligands, recent research has unveiled its crucial involvement in the realm of cancer.

The physiological importance of ROR1 lies in embryonic development, where it contributes to the establishment of the nervous system, cardiovascular system, and skeletal structure. As development progresses, ROR1's activity tends to diminish, becoming scarce within most adult cells. Remarkably, certain cancer cells, including chronic lymphocytic leukemia, malignant melanoma, and breast cancer, exhibit a re-emergence of ROR1 expression. This resurgence is closely associated with the proliferation, invasion, and metastasis of these malignant cells.

The Structure of ROR1

ROR1 (Receptor Tyrosine Kinase-like Orphan Receptor 1) exhibits a multifaceted structural configuration, comprising distinct functional domains encompassing an extracellular domain, a transmembrane domain, and an intracellular kinase domain.

Extracellular Domain: The extracellular domain of ROR1 is a complex assembly encompassing several domains, including immunoglobulin (Ig) and Kringle domains. These domains orchestrate the interaction between ROR1 and other molecules, potentially influencing its signaling prowess and ligand-binding capabilities.

Transmembrane Region: Situated at the intersection of the cell membrane's inner and outer realms, the transmembrane region is pivotal in bridging the extracellular and intracellular domains through an α-helix embedded in the membrane. This region assumes a critical role in determining receptor localization, stability, and the facilitation of signaling mechanisms.

Intracellular Kinase Domain: The intracellular segment of ROR1 houses a tyrosine kinase domain replete with enzymatic activity. This kinase domain carries out the phosphorylation of specific tyrosine residues within the receptor protein, thereby serving as the ignition point for initiating intricate intracellular signaling pathways.

Despite the ongoing enigma surrounding the exact operational framework and ligand interactions of ROR1, investigations have illuminated its potential to influence essential cellular functions such as proliferation, survival, and migration. These effects stem from the activation of complex intracellular signaling cascades, including the Wnt signaling pathway and the NF-κB signaling pathway. Notably, in select cancer contexts, the re-expression of ROR1 emerges as a correlate of tumor progression and malignancy, further underscoring its relevance.

Function of ROR1

Numerous studies have unveiled the heightened expression of ROR1 (Receptor Tyrosine Kinase-like Orphan Receptor 1) within malignant cells, marking a pivotal link to various malignancies' intricate web. This section explores the diverse roles and implications of ROR1's expression across a spectrum of cancer types.

ROR1's impact looms large in the context of certain hematological malignancies. Notably, its expression emerges as a potent prognostic factor in Chronic Lymphocytic Leukemia (CLL) patients. Moreover, a subgroup of B Acute Lymphoblastic Leukemia (B-ALL) patients harboring t(1;19) chromosomal translocation showcased ROR1 expression. Significantly, in these B-ALL cases, siRNA-mediated ROR1 suppression led to vulnerability, underscoring ROR1's pivotal role in sustaining leukemia-cell survival. ROR1's aberrant presence in Mantle Cell Lymphoma (MCL) also kindles pro-survival signals akin to those seen in CLL and B-ALL. Other non-Hodgkin lymphomas (NHL) like Diffuse Large B Cell Lymphoma (DLBCL), Follicular Lymphoma, and Marginal Zone Lymphoma exhibit ROR1 expression as well, although its precise implications remain less defined.

ROR1's influence extends beyond hematological malignancies, spanning a gamut of solid tumors as a telling biomarker and a potential therapeutic target. Breast cancer presents ROR1 positivity in tumor specimens, distinguishing them from normal breast tissues. Heightened ROR1 expression within Breast Adenocarcinoma aligns with epithelial-mesenchymal transition (EMT), fostering tumor metastasis and aggressive disease. In the realm of Lung Cancer, elevated ROR1 levels emerge as a prognostic biomarker in Lung Adenocarcinoma patients. Suppression of ROR1 engenders growth inhibition in cell lines representative of human lung adenocarcinoma. Ovarian cancer showcases tumor cells with heightened ROR1 expression adopting stem cell-like gene-expression traits and enhanced engraftment potential in immunodeficient mice. Notably, ROR1's imprint extends further, with indications of its presence across other malignancies including Colorectal Cancer, Endometrial Cancer, Gastric Cancer, Melanoma, and Pancreatic Cancer.

ROR1's Role Across Solid Malignancies: A Comprehensive Exploration

Variety of Expression in Solid Tumors

The amplified presence of ROR1 is a notable feature across a diverse array of solid malignancies. Examination through tissue microarray analysis has uncovered robust staining of ROR1 in over 30% of primary samples from colon, lung, and pancreatic cancers. Conversely, ovarian, lymphoma, skin, testicular, uterine, prostate, and adrenal cancers display moderate staining. In-depth RNAi-based scrutiny in HeLa cells has illuminated ROR1's pivotal involvement in the regulation of apoptosis. Within the sphere of lung adenocarcinoma, NKX2-1 (TITF1) stands as the driver of ROR1 expression. The subsequent upsurge in ROR1 holds two distinct proposed functions: amplification of EGF ligand-induced EGFR signaling and the phosphorylation and activation of c-Src, irrespective of ligand induction. Notably, researchers have observed mild to moderate autophosphorylation of ROR1. However, this autophosphorylation remains elusive when immunoprecipitated ectopic ROR1 is employed in COS-7 cells. Another study has identified phosphorylated ROR1 in a spectrum of cell lines, where this phosphorylation is governed by MET (HGFR), but not EGFR or ERBB2. In non-small cell lung cancer cells (NCI-H1993), ROR1 silencing disrupts the escape from anoikis and curbs anchorage-dependent programmed cell death, leading to diminished primary tumor growth when transplanted into nude mice. Furthermore, Wnt5a, not Wnt3a, binds to ROR1, which in turn recruits Frizzled 4 (FZD4) through FZD4’s CRD. This transitory localization enables FZD4-associated glycogen synthase kinase 3β (GSK3β) to phosphorylate ROR1 on Ser/Thr residues, suggesting ROR1's potential to function as a shared node for kinase phosphorylation, facilitating subsequent pathway activation via adaptor/effector protein recruitment.

Inroads into Breast Cancer Dynamics

Shifting attention to breast cancer, ROR1's presence is evident in neoplastic breast cancer cells while absent in stromal cells. Moreover, heightened ROR1 expression aligns with elevated grade and heightened disease aggression. The stimulation of ROR1 by recombinant Wnt5a leads to an interaction with casein kinase 1ε (CK1ε). Subsequent interaction with phosphoinositide 3-kinase (PI3K) culminates in the phosphorylation of AKT and CREB. Elevated ROR1 levels in patients and cell lines correlate with genes participating in epithelial-mesenchymal transition (EMT), such as ZEB1 and vimentin. Conversely, ROR1 inversely associates with adherent junction proteins. The silencing of ROR1 in triple-negative-derived cell lines attenuates EMT genes, including SNAI1, SNAI2, ZEB1, and vimentin. In the triple-negative breast cancer cell line MDA-MB-231, ROR1 knockdown via small hairpin (sh) RNA curtails in vitro cell migration and reduces bone and lung foci size in xenografts.

Significant Signatures in Renal Cancer and Melanoma

While protein levels of ROR1 are usually undetectable within healthy kidneys, ROR1 mRNA emerges in 81.3% of renal cancer tissue samples and 94% of PBMCs samples from renal cancer patients, as evidenced by RT-PCR. Furthermore, PBMCs from renal cancer patients exhibit markedly higher ROR1 expression than healthy controls. This pattern underscores ROR1's potential as a hallmark of renal cancer, although protein levels remain unmeasured. Across multiple melanoma cell lines, ROR1 expression emerges upon assessment through RT-PCR, Western blot, and flow cytometry. Silencing ROR1 triggers apoptosis across all tested melanoma cell lines. Notably, a complex paradigm emerges within melanoma cell lines, where the association of ROR1 expression with a proliferative signature coexists with correlations to a non-invasive phenotype. Treatment of poorly invasive cell lines with recombinant Wnt5a leads to diminished ROR1 expression and overall protein levels. Intriguingly, ROR1 silencing elevates Wnt5a and ROR2 expression, supporting a more invasive phenotype. The differential regulation of ROR1 and ROR2 is also evidenced under hypoxic conditions, with decreased ROR1 expression and heightened ROR2 expression prevailing.

Decoding ROR1's Intricate Signaling Pathways

ROR1's Influence on the Wnt Signaling Pathway

The Wnt signaling pathway is a highly conserved cell signaling pathway that regulates embryonic development, tissue regeneration, and cellular function in adulthood. There is an association between ROR1 and the Wnt signaling pathway.

In the Wnt signaling pathway, Wnt protein is a signaling molecule that triggers a series of signaling events by binding to Frizzled receptors and Lrp co-receptors on the cell membrane. This leads to the accumulation of β-catenin in the nucleus, activates Tcf/Lef transcription factors, and promotes the transcription of target genes, thereby affecting cell fate, proliferation, and differentiation. ROR1 plays an important role in this process, and it is considered a regulator of the Wnt signaling pathway. ROR1 can interact with Wnt protein and promote the activation of Wnt signaling pathway. Studies have shown that ROR1 can bind to Wnt5a, thereby activating small Rho family GTPases, affecting cell polarity, migration and adhesion. In addition, ROR1 can also affect the self-renewal and differentiation of stem cells by regulating the molecular mechanism of Wnt/β-catenin signaling pathway.

In summary, the role of ROR1 in the Wnt signaling pathway is very complex. It not only participates in the activation of the Wnt signaling pathway, but also regulates the transduction of Wnt/β-catenin signals through different molecular mechanisms, affecting cell fate and function.

ROR1's Nexus with the NF-κB Signaling Pathway

The NF-κB signaling pathway is an important cell signaling pathway involved in the regulation of immune responses, inflammation and cell survival. There is an interaction between ROR1 and NF-κB signaling pathway.

Studies have shown that ROR1 can affect the activation of NF-κB signaling pathway. In some cancer cells, overexpression of ROR1 can lead to overactivation of NF-κB signaling pathway. This may be through ROR1-mediated signaling events, leading to the enhancement of NF-κB activity, thereby affecting cellular functions such as inflammatory response, cell proliferation and survival. In addition, NF-κB signaling pathway can also regulate the expression of ROR1. NF-κB can directly or indirectly affect the transcription of ROR1 gene, thereby regulating the expression level of ROR1 protein. This regulation may be related to biological processes such as inflammation and immune response. The interaction between ROR1 and NF-κB signaling pathway may be of great significance in the occurrence and development of cancer. This interaction may affect key processes such as tumor cell survival, proliferation, metastasis, and immune escape.

Clinical Implications of Targeting ROR1

Targeting ROR1 is of clinical importance, especially in the field of cancer therapy. The expression of ROR1 in cancer is closely related to tumor development, malignancy and prognosis, so researchers are exploring the possibility of using it as a therapeutic target. The following are several aspects of the clinical significance of targeting ROR1:

1. New therapeutic targets: ROR1 is overexpressed in many cancer types, including chronic lymphocytic leukemia, breast cancer, lung cancer, and malignant melanoma. This makes it a potential therapeutic target, especially for those tumor types that lack effective treatment options.
2. Individualized treatment strategy: The treatment strategy targeting ROR1 can be individually designed according to the tumor expression status of the patient. By detecting the expression level of ROR1 in the patient's tumor, the most suitable treatment plan can be selected and the treatment effect can be improved.
3. Inhibition of tumor growth and metastasis: ROR1 plays a role in the proliferation, survival and migration of tumor cells. Therefore, inhibiting the activity of ROR1 may prevent tumor growth and metastasis, thereby reducing the deterioration of the disease.
4. Drug development: Scientists are studying drugs targeting ROR1, such as antibody drugs, small molecule inhibitors, etc., in order to achieve effective tumor treatment. The development of these drugs may provide new treatment options for patients who do not respond to conventional therapies or are resistant to them.
5. Prognostic indicators: Clinical studies have shown that the expression of ROR1 is related to the prognosis of patients. By analyzing the expression of ROR1 in tumors, the survival period and risk of disease progression of patients can be predicted to guide treatment decisions.

In conclusion, targeting ROR1 has potential clinical significance in cancer therapy, which can provide patients with individualized treatment strategies, inhibit tumor growth and metastasis, enhance the effect of immunotherapy, and provide new avenues for drug development and prognosis assessment.

ROR1 Protein

Recombinant Human Inactive Tyrosine-Protein Kinase Transmembrane Receptor Ror1 (ROR1) Protein (His), Active

Excellent Bioactivity Validated by Functional ELISA

Click here for more ROR1

Synonym : dJ537F10.1 Inactive tyrosine protein kinase transmembrane receptor ROR1 MGC99659 Neurotrophic tyrosine kinase Neurotrophic tyrosine kinase receptor related 1 Neurotrophic tyrosine kinase, receptor related 1 NTRKR1 OTTHUMP00000010573 OTTHUMP00000010574 OTTMUSP00000008344 Receptor tyrosine kinase like orphan receptor 1 receptor-related 1 RGD1559469 ROR 1 ROR1 ROR1_HUMAN RP11 24J23.1 Tyrosine kinase like orphan receptor 1 Tyrosine protein kinase transmembrane receptor ROR1 Tyrosine-protein kinase transmembrane receptor ROR1

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