The ERK1/2 (RAS, RAF, MEK, ERK) and PI3K (PI3K, AKT, mTOR, PTEN) pathways are the chief signaling pathways for cellular proliferation, survival, and differentiation. Overactivation and hyperphosphorylation of the ERK1/2 & PI3K pathways is frequently observed in cancer and is associated with poor patient prognosis. While it is well known that genetic alterations lead to the dysregulation of the ERK1/2 & PI3K pathways, increasing evidence showcase that epigenetic alterations also play a major role in the regulation of the ERK1/2 & PI3K pathways. Protein Arginine Methyltransferase 5 (PRMT5) is a posttranslational modifier for multiple cellular processes, which is currently being tested as a therapeutic target for cancer. PRMT5 has been shown to be overexpressed in many types of cancers, as well as negatively correlated with patient survival. Numerous studies are indicating that as a posttranslational modifier, PRMT5 is extensively involved in regulating the ERK1/2 & PI3K pathways. In addition, a large number of in vitro and in vivo studies are demonstrating that PRMT5 inhibition, as well as PRMT5 and ERK1/2 & PI3K combination therapies, show significant therapeutic effects in many cancer types. In this review, we explore the vast interactions that PRMT5 has with the ERK1/2 & PI3K pathways, and we make the case for further testing of PRMT5 inhibition, as well as PRMT5 and ERK1/2 & PI3K combination therapies, for the treatment of cancer.

Nearly 45% of colorectal cancer (CRC) patients harbor a mutation in their KRAS gene for which, despite many years of research, there are still no targeted therapies available. Protein Arginine Methyltransferase 5 (PRMT5) is a transcription regulator for multiple cellular processes that is currently being tested as a potential target in several cancer types. PRMT5 has been previously shown to be overexpressed in approximately 75% of CRC patient tumor samples, as well as negatively correlated with CRC patient survival. Here, we provide evidence that PRMT5 can act as a surrogate target for mutated KRAS in CRC. Our findings show that PRMT5 expression is upregulated, as well as positively correlated with KRAS expression, in CRC patient datasets. Moreover, our results reveal that PRMT5 is further overexpressed in KRAS mutant CRC cells when compared to KRAS wild type (WT) CRC cells at both the transcriptional and translational levels. Additionally, our data demonstrate that this further overexpression of PRMT5 in the KRAS mutant CRC cells affects an even greater degree of growth inhibition, apoptosis, and cell cycle arrest, following treatment with PRMT5 inhibitor, when compared to the KRAS WT CRC cells. Our research therefore suggests for the first time that PRMT5 and KRAS may crosstalk, and thus, PRMT5 can potentially be used as a surrogate target for mutated KRAS in CRC.

Despite decades of research, there are still no effective targeted treatments for the nearly 45% of colorectal cancer (CRC) patients harboring a mutation in their KRAS gene. Protein Arginine Methyltransferase 5 (PRMT5) is an epigenetic regulator undergoing clinical trials as a potential therapeutic target for cancer. Our group has previously reported that PRMT5 is overexpressed in KRAS mutant CRC when compared to KRAS wild-type (WT) CRC, and that PRMT5 inhibition exhibited greater therapeutic efficacy in KRAS mutant CRC when compared to KRAS WT CRC. We therefore proposed that PRMT5 may be a strong therapeutic target for KRAS mutant CRC, and that PRMT5 and KRAS may crosstalk. In this study, we investigated several key downstream signal transduction proteins that may be involved in mediating the potential crosstalk between PRMT5 and KRAS. This is important, as these key intermediate proteins may be strong therapeutic targets for inhibition, as well as valuable therapeutic targets for combination therapy along with PRMT5 inhibitors. We first conducted a literature review to determine which key downstream proteins may be involved in mediating the potential crosstalk between PRMT5 and KRAS. Our initial findings indicated that MYC, p65/RELA, TP53, P21/CDKN1A, ELF1, E2F1, and EIF4E may be key downstream proteins involved in mediating the potential crosstalk between PRMT5 and KRAS. We next used the STRING database to determine which of the aforementioned proteins have demonstrated interactions with PRMT5 and KRAS. We found that PRMT5 and KRAS both interact with MYC, p65/RELA, TP53, P21/CDKN1A, E2F1, and EIF4E with an interaction score > 0.150. We then used the Gene Expression Profiling Interactive Analysis (GEPIA) database to analyze the RNA-Seq data of CRC patients from The Cancer Genome Atlas (TCGA) database. We first used the GEPIA database to determine which proteins are overexpressed in CRC patient tumor samples compared to normal colon and rectum patient samples. We observed that MYC, TP53, E2F1, and EIF4E are all over 2-fold overexpressed in CRC patient tumor samples compared to normal colon and rectum patient samples (q < 0.01). We next used the GEPIA database to determine which proteins have an expressional correlation with PRMT5 and KRAS in CRC patient tumor samples. We found that MYC, E2F1, and EIF4E are all positively correlated with PRMT5 and KRAS with an R-Value > 0.70 and a P-Value < 0.01 in CRC patient tumor samples. Our study thus showcases the key downstream signal transduction proteins that may be involved in mediating the potential crosstalk between PRMT5 and KRAS. These findings are significant, as these key intermediate proteins may be strong therapeutic targets for inhibition, as well as strong therapeutic targets for a PRMT5 combination therapy. Additional research is currently underway to outline the molecular processes behind MYC, E2F1, and EIF4E’s interactions with both PRMT5 and KRAS. Citation Format: David Shifteh, Tzuriel Sapir, Moshe Pahmer, Sanjay Goel, Radhashree Maitra. PRMT5 inhibition as a therapeutic strategy for KRAS mutant CRC: downstream mediators of the PRMT5-KRAS crosstalk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 534.

The ERK1/2 and PI3K pathways are the chief signaling pathways for cellular proliferation, survival, and differentiation. Overactivation of the ERK1/2 & PI3K pathways is commonly seen in cancer and is associated with poor patient prognosis. Increasing evidence is showcasing that epigenetic alterations play a major role in regulating the ERK1/2 & PI3K pathways. Protein Arginine Methyltransferase 5 (PRMT5) is an epigenetic regulator currently undergoing clinical trials as a potential therapeutic target for cancer. PRMT5 has been shown to be overexpressed and negatively correlated with patient survival in many types of cancers. Recent studies are indicating that PRMT5 is involved in regulating the ERK1/2 & PI3K pathways. Moreover, our group's work, as well as other studies, are demonstrating that PRMT5 inhibition, as well as PRMT5 and ERK1/2 & PI3K combination therapies, show significant therapeutic effects in many types of cancers. In this study, the Gene Expression Profiling Interactive Analysis (GEPIA) database was used to analyze the RNA-Seq data of colorectal cancer (CRC) patients from The Cancer Genome Atlas (TCGA) database. We first used the GEPIA database to determine which proteins in the ERK1/2 & PI3K pathways are expressionally correlated with PRMT5 in colon and rectum patient tumor samples. We found that the receptor proteins EGFR and FGFR3 were positively correlated with PRMT5 with a R-Value > 0.61 and a P-Value < 0.01. We further determined that the ERK1/2 pathway proteins KRAS, RAF, MEK, and ERK were all positively correlated with PRMT5 with a R-Value > 0.73 and a P-Value < 0.01. Lastly, we found that the PI3K pathway proteins PI3K, AKT, mTOR, and PTEN were positively correlated with PRMT5 with a R-Value > 0.71 and a P-Value < 0.01. We next used the STRING database to analyze and determine which proteins in the ERK1/2 & PI3K pathways interact with PRMT5. We found that PRMT5 interacts with the receptor proteins EGFR and FGFR3, the ERK1/2 pathway proteins KRAS, and lastly, the PI3K pathway proteins AKT, mTOR, and PTEN with an interaction score > 0.150. Finally, we then used Biorender to develop a protein network map to model the proteins in the ERK1/2 & PI3K pathways that both positively correlate with, as well as interact with, PRMT5. Our protein network map demonstrates that PRMT5 is positively correlated with (R-Value > 0.61, P-Value < 0.01), as well as interacts with (interaction score > 0.150) the following ERK1/2 & PI3K pathway proteins: EGFR, FGFR3, KRAS, AKT, mTOR, and PTEN. Our study thus shows further evidence that PRMT5 is positively correlated with, as well as interacts with, the ERK1/2 & PI3K pathways in CRC. These findings are significant as they make the case for additional testing of PRMT5 inhibition, as well as PRMT5 and ERK1/2 & PI3K combination therapies, for the treatment of cancer. Further analysis is currently in progress to delineate the molecular mechanisms behind PRMT5’s interactions with the ERK1/2 & PI3K pathways. Citation Format: David Shifteh, Tzuriel Sapir, Moshe Pahmer, Sanjay Goel, Radhashree Maitra. PRMT5 is positively correlated with and interacts with the ERK1/2 & PI3K Pathways in CRC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3369.

Introduction Nearly 45% of colorectal cancer (CRC) patients harbor a mutation in their KRAS gene for which, despite many years of research, there are still no targeted therapies available. Protein Arginine Methyltransferase 5 (PRMT5) is a transcription regulator for multiple cellular processes that is currently being tested as a potential therapeutic target in several cancer types. Previous studies have shown that PRMT5 depletion leads to a reduction in FGFR3 and eIF4E expression. FGFR3 and eIF4E are oncogenes which play an important role in cellular proliferation and tumorigenesis. Furthermore, our group's previous research has demonstrated that PRMT5 inhibition shows significantly greater therapeutic effects in KRAS mutant CRC cells when compared to KRAS wild-type (WT) CRC cells. Methodology The Gene Expression Profiling Interactive Analysis (GEPIA) database was used to analyze the RNA-Seq data of CRC patients from The Cancer Genome Atlas (TCGA) database. We first used the GEPIA database to determine whether eIF4E and FGFR3 are overexpressed in colon and rectum patient tumor samples when compared to normal colon and rectum patient samples. We then used the GEPIA database to determine whether eIF4E and FGFR3 gene expression are correlated with PRMT5 and KRAS gene expression in colon and rectum patient tumor samples. We next used the STRING database to analyze whether eIF4E and FGFR3 interact with PRMT5 and KRAS. Finally, we used Biorender to develop a proposed molecular mechanism outlining how eIF4E and FGFR3 interact with PRMT5 and KRAS in CRC. Results • eIF4E is 2.4 and 2.2-Fold overexpressed in colon and rectum patient tumor samples, respectively, compared to normal colon and rectum patient samples (q < 0.01). • FGFR3 is 2.3 and 3.7-Fold overexpressed in colon and rectum patient tumor samples, respectively, compared to normal colon and rectum patient samples (q < 0.01). • eIF4E gene expression is positively correlated with PRMT5 (p < 0.01, R = 0.85) and KRAS (p < 0.01, R = 0.86) gene expression in colon and rectum patient tumor samples. • FGFR3 gene expression is positively correlated with PRMT5 (p < 0.01, R = 0.61) and KRAS (p < 0.01, R = 0.63) gene expression in colon and rectum patient tumor samples. • eIF4E and FGFR3 are shown to interact with PRMT5 and KRAS in the STRING database (Interaction score > 0.150). • A molecular mechanism is proposed suggesting that PRMT5 inhibition may show greater therapeutic effects in KRAS mutant CRC, when compared to KRAS WT CRC, through PRMT5's interactions with eIF4E and FGFR3. Conclusion eIF4E and FGFR3 have been shown to be overexpressed and to interact with PRMT5 and KRAS in CRC. This significant observation can be therapeutically utilized towards developing new effective treatments for KRAS mutant CRC patients. Further analysis is currently in progress to verify the proposed molecular mechanism outlining how eIF4E and FGFR3 interact with PRMT5 and KRAS in CRC. Citation Format: David Shifteh, Tzuriel Sapir, Moshe Pahmer, Sanjay Goel, Radhashree Maitra. FGFR3 and eIF4E are overexpressed and interact with PRMT5 and KRAS in CRC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 961.