A novel RON splice variant lacking exon 2 activates the PI3K/AKT pathway via PTEN phosphorylation in colorectal carcinoma cells
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Yu Ling1, Yeye Kuang2, Lin-Lin Chen1
1Department of Colorectal Surgery, Sir Run Run Shaw Hospital, Zhejiang University of Medicine, Hangzhou, Zhejiang 310016, People's Republic of China.
Abstract:
Abnormal expression of the Recepteur d'Origine Nantais (RON) receptor tyrosine kinase is accompanied by the generation of multiple splice or truncated variants, which mediate many critical cellular functions that contribute to tumor progression and metastasis. Here, we report a new RON splice variant in the human colorectal cancer (CRC) cell line HT29. This variant is a 165 kda protein generated by alternative pre-mRNA splicing that eliminates exon 2, causing an in-frame deletion of 63 amino acids in the extracellular domain of the RON β chain. The deleted transcript was a single chain expressed in the intracellular compartment. Although it lacked tyrosine phosphorylation activity, the RONΔ165E2 variant could phosphorylate phosphatase and tensin homolog (PTEN), thereby activating the PI3K/AKT pathway. In addition, in vitro and in vivo experiments showed that the RONΔ165E2 promoted cell migration and tumor growth. Finally, in an investigation of 67 clinical CRC samples, the variant was highly expressed in about 58% of the samples, and was positively correlated with the invasive depth of the tumor (P < 0.05). These results demonstrate that the novel RONΔ165E2 variant promoted tumor progression while activating the PI3K/AKT pathway via PTEN phosphorylation.
Insights
A novel variant of the Recepteur d'Origine Nantais (RON) receptor tyrosine kinase, RONΔ165E2, promotes colorectal cancer progression and metastasis. This variant activates the PI3K/AKT pathway by phosphorylating PTEN, and is highly expressed in clinical CRC samples.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Receptor tyrosine kinases, including Recepteur d'Origine Nantais (RON), play critical roles in cancer progression.
- Aberrant splicing and truncated variants of RON are associated with tumor metastasis.
- Understanding novel splice variants is crucial for targeted cancer therapies.
Purpose of the Study:
- To identify and characterize a novel splice variant of RON in colorectal cancer (CRC).
- To investigate the functional role of the new variant in tumor progression and metastasis.
- To explore the molecular mechanisms underlying the variant's oncogenic activity.
Main Methods:
- Alternative pre-mRNA splicing analysis in HT29 CRC cell line.
- Protein characterization of the novel RON variant (RONΔ165E2).
- In vitro and in vivo assays for cell migration and tumor growth.
- Western blotting and immunohistochemistry for PTEN and PI3K/AKT pathway analysis.
- Analysis of clinical CRC samples for variant expression and correlation with tumor invasion.
Main Results:
- A new RON splice variant, RONΔ165E2 (165 kDa), was identified, resulting from exon 2 deletion.
- RONΔ165E2 lacks intrinsic tyrosine kinase activity but phosphorylates PTEN, activating the PI3K/AKT pathway.
- The variant significantly promoted cell migration and tumor growth in vitro and in vivo.
- RONΔ165E2 was highly expressed in 58% of clinical CRC samples and correlated with increased tumor invasion depth.
Conclusions:
- The novel RONΔ165E2 splice variant is a driver of colorectal cancer progression and metastasis.
- Activation of the PI3K/AKT pathway via PTEN phosphorylation is a key mechanism for RONΔ165E2's oncogenic function.
- RONΔ165E2 represents a potential therapeutic target for colorectal cancer.