SHP-1 Activity Research Articles

Neonatal malnutrition impacts fibroblast growth factor 21-induced neuron neurite outgrowth and growth hormone-releasing hormone secretion in neonatal mouse brain

Neonatal malnutrition is one of the most common causes of neurological disorders. However, the mechanism of action of the factors associated with neonatal nutrition in the brain remains unclear. In this study, we focused on fibroblast growth factor (FGF) 21 to elucidate the effects of malnutrition on the neonatal brain. FGF21 is an endocrine factor produced by the liver during lactation which is the main source of nutrition during the neonatal period. In this study, malnourishment during nursing mice induced decreased levels of Fgf21 mRNA in the liver and decreased levels of FGF21 in the serum. RNA-seq analysis of neonatal mouse brain tissue revealed that FGF21 controlled the expression of Kalrn-201 in the neonatal mouse brain. Kalrn-201 is a transcript of Kalirin, a Ras homologous guanine nucleotide exchange factor at the synapse. In mouse neurons, FGF21 induced the expression of Kalirin-7 (a Kalirin isoform) by down-regulating Kalrn-201. FGF21-induced Kalirin-7 stimulated neurite outgrowth in Neuro-2a cells. FGF21 also induced Growth hormone-releasing hormone (GHRH) expression in Neuro-2a cells. Kalirin-7 and GHRH expression induced by FGF21 was altered by inhibiting the activity of SH2-containing tyrosine phosphatase (SHP2) which is located downstream of the FGF receptor (FGFR). Additionally, malnourished nursing induced intron retention of the SHP2 gene (Ptpn11), resulting in the alteration of Kalirin-7 and GHRH expression by FGF21 signaling. Ptpn11 intron retention is suggested to be involved in regulating SHP2 activity. Taken together, these results suggest that FGF21 plays a critical role in the induction of neuronal neurite outgrowth and GHRH secretion in the neonatal brain, and this mechanism is regulated by SHP2. Thus, Ptpn11 intron retention induced by malnourished nursing may be involved in SHP2 activity.

An autonomous activation of interleukin-17 receptor signaling sustains inflammation and promotes disease progression

Anti-interleukin-17 (IL-17) therapy has been used in various autoimmune diseases. However, the efficacy is unexpectedly limited in several IL-17-associated diseases, and the mechanism of limited efficacy remains unclear. Here, we show that a molecular complex containing the adaptor molecule Act1 and tyrosine phosphatase SHP2 mediated autonomous IL-17R signaling that accelerated and sustained inflammation. SHP2, aberrantly augmented in various autoimmune diseases, was induced by IL-17A itself in astrocytes and keratinocytes, sustaining chemokine production even upon anti-IL-17 therapies. Mechanistically, SHP2 directly interacted with and dephosphorylated Act1, which replaced Act1-TRAF5 complexes and induced IL-17-independent activation of IL-17R signaling. Genetic or pharmacologic inactivation of SHP2, or blocking Act1-SHP2 interaction, paralyzed both IL-17-induced and IL-17-independent signaling and attenuated primary or relapsing experimental autoimmune encephalomyelitis. Therefore, Act1-SHP2 complexes mediate an alternative pathway for autonomous activation of IL-17R signaling, targeting which could be a therapeutic option for IL-17-related diseases in addition to current antibody therapies.

In silico mutagenesis-based designing of oncogenic SHP2 peptide to inhibit cancer progression

Cancer is among the top causes of death, accounting for an estimated 9.6 million deaths in 2018, it appeared that approximately 500,000 people die from cancer in the United States alone annually. The SHP2 plays a major role in regulation of cell growth, proliferation, and differentiation, and functional upregulation of this enzyme is linked to oncogenesis and developmental disorders. SHP2 activity has been linked to several cancer types for which no drugs are currently available. In our study, we aimed to design peptide inhibitors against the SHP2 mutant. The crystal structure of the human Src SH2-PQpYEEIPI peptide mutant was downloaded from the protein databank. We generated several peptides from the native wild peptide using an in silico mutagenesis method, which showed that changes (P302W, Y304F, E306Q, and Q303A) might boost the peptide's affinity for binding to SHP2. Furthermore, the dynamical stability and binding affinities of the mutated peptide were confirmed using Molecular dynamics simulation and Molecular Mechanics with Generalized Born and Surface Area Solvation free energy calculations. The proposed substitution greatly enhanced the binding affinity at the residue level, according to a study that decomposed energy into its component residues. Our proposed peptide may prevent the spread of cancer by inhibiting SHP2, according to our detailed analyses of binding affinities.

Marine alkaloid rigidin analogues as potential selective inhibitors of SHP1, a new strategy for cancer immunotherapeutics

SHP1 is a protein tyrosine phosphatase playing a central role in immunity, cell growth, development, and survival. The inhibition of SHP1 can help in better prognosis in various disorders like breast and ovarian cancer, melanoma, atherosclerosis, hypoxia, hypoactive immune response, and familial dysautonomia. The currently available inhibitors of SHP1 have the side effect of inhibiting the activity of SHP2, which shares >60% sequence similarity with SHP1 but has distinct biological functions. Thus, there is a need to search for novel specific inhibitors of SHP1. The current study uses a combination of virtual screening and molecular dynamic simulations, followed by PCA and MM-GBSA analysis, to screen about 35000 compounds; to predict that two rigidin analogues can potentially selectively inhibit SHP1 but not SHP2. Our studies demonstrate that these rigidin analogues are more potent at inhibiting SHP1 than the commercially available inhibitor NSC-87877. Further, cross-binding studies with SHP2 exhibited poor binding efficiency and lower stability of the complex, thus indicating a specificity of the rigidin analogues for SHP1, which is crucial in preventing side effects due to the diverse physiological functions of SHP2 in cellular signaling, proliferation, and hematopoiesis. Additionally, SHP1 is essential in mediating the inhibitory signaling in antitumor immune cells like NK and T cells. Hence, the rigidin analogues that inhibit SHP1 will potentiate the anti-tumor immune response by the release of inhibitory function of NK cells, thus driving NK activating response, in addition to their intrinsic anti-tumor function. Thus, SHP1 inhibition is a novel double-blade approach towards anti-cancer immunotherapeutics. Communicated by Ramaswamy H. Sarma

Cathepsin K inhibition induces Raptor destabilization and mitochondrial dysfunction via Syk/SHP2/Src/OTUB1 axis-mediated signaling

The Raptor signaling pathway is a critical point of intervention in the invasion and progression of cancer. The non-receptor tyrosine kinase Src-mediated phosphorylation of OTUB1-Y26 plays a critical role in Raptor stabilization, whereas cathepsin K inhibitor (odanacatib; ODN) and knockdown (siRNA) induce Raptor destabilization. However, the mechanisms involved in cathepsin K inhibition-induced OTUB1-Y26 phosphorylation in Raptor stabilization have not been yet elucidated. This study showed that cathepsin K inhibition activates SHP2, a tyrosine phosphatase, that dephosphorylates OTUB1 and destabilizes Raptor, whereas SHP2 deletion and pharmacological inhibition increase OTUB1-Y26 phosphorylation and Raptor expression. SHP2 deletion also led to the inhibition of ODN-induced mitochondrial ROS, fusion, and dysfunction. Furthermore, cathepsin K inhibition phosphorylated spleen tyrosine kinase (Syk) at Y525 and Y526, resulting in the SHP2-mediated dephosphorylation of OTUB1-Y26. Collectively, our findings identified Syk not only as an upstream tyrosine kinase required for SHP2 activation but also showed a critical mechanism that regulates ODN-induced Raptor downregulation and mitochondrial dysfunction. In conclusion, Syk/SHP2/Src/OTUB1 axis-mediated signaling can act as a therapeutic target in cancer management.

Targeting pathogenic macrophages by the application of SHP-1 agonists reduces inflammation and alleviates pulmonary fibrosis

Idiopathic pulmonary fibrosis is a progressive fibrotic disorder with no cure that is characterized by deterioration of lung function. Current FDA-approved drugs for IPF delay the decline in lung function, but neither reverse fibrosis nor significantly improve overall survival. SHP-1 deficiency results in hyperactive alveolar macrophages accumulating in the lung, which contribute to the induction of pulmonary fibrosis. Herein, we investigated whether employing a SHP-1 agonist ameliorates pulmonary fibrosis in a bleomycin-induced pulmonary fibrosis murine model. Histological examination and micro-computed tomography images showed that SHP-1 agonist treatment alleviates bleomycin-induced pulmonary fibrosis. Reduced alveolar hemorrhage, lung inflammation, and collagen deposition, as well as enhanced alveolar space, lung capacity, and improved overall survival were observed in mice administered the SHP-1 agonist. The percentage of macrophages collected from bronchoalveolar lavage fluid and circulating monocytes in bleomycin-instilled mice were also significantly reduced by SHP-1 agonist treatment, suggesting that the SHP-1 agonist may alleviate pulmonary fibrosis by targeting macrophages and reshaping the immunofibrotic niche. In human monocyte-derived macrophages, SHP-1 agonist treatment downregulated CSF1R expression and inactivated STAT3/NFκB signaling, culminating in inhibited macrophage survival and perturbed macrophage polarization. The expression of pro-fibrotic markers (e.g., MRC1, CD200R1, and FN1) by IL4/IL13-induced M2 macrophages that rely on CSF1R signaling for their fate-determination was restricted by SHP-1 agonist treatment. While M2-derived medium promoted the expression of fibroblast-to-myofibroblast transition markers (e.g., ACTA2 and COL3A1), the application of SHP-1 agonist reversed the transition in a dose-dependent manner. Our report indicates that pharmacological activation of SHP-1 ameliorates pulmonary fibrosis via suppression of CSF1R signaling in macrophages, reduction of pathogenic macrophages, and the inhibition of fibroblast-to-myofibroblast transition. Our study thus identifies SHP-1 as a druggable target for the treatment of IPF, and suggests that the SHP-1 agonist may be developed as an anti-pulmonary fibrosis medication that both suppresses inflammation and restrains fibroblast-to-myofibroblast transition.

Exploration of T cell immune responses by expression of a dominant-negative SHP1 and SHP2.

SHP1 and SHP2 are SH2 domain-containing proteins which have inhibitory phosphatase activity when recruited to phosphorylated ITIMs and ITSMs on inhibitory immune receptors. Consequently, SHP1 and SHP2 are key proteins in the transmission of inhibitory signals within T cells, constituting an important point of convergence for diverse inhibitory receptors. Therefore, SHP1 and SHP2 inhibition may represent a strategy for preventing immunosuppression of T cells mediated by cancers hence improving immunotherapies directed against these malignancies. Both SHP1 and SHP2 contain dual SH2 domains responsible for localization to the endodomain of inhibitory receptors and a protein tyrosine phosphatase domain which dephosphorylates and thus inhibits key mediators of T cell activation. We explored the interaction of the isolated SH2 domains of SHP1 and SHP2 to inhibitory motifs from PD1 and identified strong binding of both SH2 domains from SHP2 and more moderate binding in the case of SHP1. We next explored whether a truncated form of SHP1/2 comprising only of SH2 domains (dSHP1/2) could act in a dominant negative fashion by preventing docking of the wild type proteins. When co-expressed with CARs we found that dSHP2 but not dSHP1 could alleviate immunosuppression mediated by PD1. We next explored the capacity of dSHP2 to bind with other inhibitory receptors and observed several potential interactions. In vivo we observed that the expression of PDL1 on tumor cells impaired the ability of CAR T cells to mediate tumor rejection and this effect was partially reversed by the co-expression of dSHP2 albeit at the cost of reduced CAR T cell proliferation. Modulation of SHP1 and SHP2 activity in engineered T cells through the expression of these truncated variants may enhance T cell activity and hence efficacy in the context of cancer immunotherapy.

THEMIS increases TCR signaling in CD4+CD8+ thymocytes by inhibiting the activity of the tyrosine phosphatase SHP1.

The T cell lineage-restricted protein THEMIS plays a critical role in T cell development at the positive selection stage. In the SHP1 activation model, THEMIS is proposed to enhance the activity of the tyrosine phosphatase SHP1 (encoded by Ptpn6), thereby dampening T cell antigen receptor (TCR) signaling and preventing the inappropriate negative selection of CD4+CD8+ thymocytes by positively selecting ligands. In contrast, in the SHP1 inhibition model, THEMIS is proposed to suppress SHP1 activity, rendering CD4+CD8+ thymocytes more sensitive to TCR signaling initiated by low-affinity ligands to promote positive selection. We sought to resolve the controversy regarding the molecular function of THEMIS. We found that the defect in positive selection in Themis-/- thymocytes was ameliorated by pharmacologic inhibition of SHP1 or by deletion of Ptpn6 and was exacerbated by SHP1 overexpression. Moreover, overexpression of SHP1 phenocopied the Themis-/- developmental defect, whereas deletion of Ptpn6, Ptpn11 (encoding SHP2), or both did not result in a phenotype resembling that of Themis deficiency. Last, we found that thymocyte negative selection was not enhanced but was instead impaired in the absence of THEMIS. Together, these results provide evidence favoring the SHP1 inhibition model, supporting a mechanism whereby THEMIS functions to enhance the sensitivity of CD4+CD8+ thymocytes to TCR signaling, enabling positive selection by low-affinity, self-ligand-TCR interactions.

The mutation PTPN6Ala455Thrcausing pulmonary emphysema affects B cell populations and causes spontaneous pulmonary tertiary lymphoid tissue formation

Abstract Rationale: A new mutation causing severe pulmonary emphysema was recently discovered in a French-Canadian family. The mutation is located in the PTPN6 gene (PTPN6 Ala455Thr) leading to a reduction in the activity of SHP-1, a phosphatase that regulates pathways associated to B cells. We aimed to characterize B cell abnormalities associated with aging in both humans and mice carrying this mutation. Methods: Circulating B cell populations in humans carrying the PTPN6Ala455Thrmutation were analyzed by flow cytometry and immunoglobulin levels were measured in serum. In mice carrying the same mutation (Ptpn6Ala457Thr) aged up to 12 months, B cell populations were analyzed by flow cytometry and lung tissue histology performed. Mice were immunized with the T cell-independent antigen and NP-specific antibodies were measured in plasma. Results: Human carriers of the PTPN6Ala455Thrmutation had reduced IgG1 and IgG4, and increased IgG3 levels as well as a lower ratio of naive B cells/ isotype switched memory B cells compared to controls. Aging Ptpn6Ala457Thrmice developed spontaneous pulmonary tertiary lymphoid tissues and exhibited higher proportion of B-1 cells, age-associated B cells and germinal center B cells along with lower B-2 cells in the lung and spleen. Ptpn6Ala457Thrmice had lower levels of NP-specific IgG1 antibodies compared to the wild-type group. Conclusion: SHP-1 appears to affect aging of B cells as the PTPN6Ala455Thrmutation leads to changes in B cell populations associated with age, tertiary lymphoid tissue formation and an alteration of immunoglobulin levels. The link between B cell abnormalities, aging and emphysema requires further investigation. Funding:CIHR, FRQS CIHR, FRQS

GRB2 promotes thymocyte positive selection by facilitating THEMIS-mediated inactivation of SHP1.

The T-lineage restricted protein THEMIS has been shown to play a critical role in T cell development. THEMIS, via its distinctive CABIT domains, inhibits the catalytic activity of the tyrosine phosphatase SHP1 (PTPN6). SHP1 and THEMIS bind to the ubiquitous cytosolic adapter GRB2, and the purported formation of a tri-molecular THEMIS-GRB2-SHP1 complex facilitates inactivation of SHP1 by THEMIS. The importance of this function of GRB2 among its numerous documented activities is unclear as GRB2 binds to multiple proteins and participates in several signaling responses in thymocytes. Here, we show that similar to Themis-/- thymocytes, the primary molecular defect in GRB2-deficient thymocytes is increased catalytically active SHP1 and the developmental block in GRB2-deficient thymocytes is alleviated by deletion or inhibition of SHP1 and is exacerbated by SHP1 overexpression. Thus, the principal role of GRB2 during T cell development is to promote THEMIS-mediated inactivation of SHP1 thereby enhancing the sensitivity of TCR signaling in CD4+CD8+ thymocytes to low affinity positively selecting self-ligands.

Abstract 873: The mechanisms of SHP2 activation in cancer and neurodevelopmental disorder

Abstract The Src homology 2 domain-containing phosphatase 2 (SHP2) is a nonreceptor protein tyrosine phosphatase that regulates Ras/MAPK pathway, leading to cell proliferation. SHP2 mutations are commonly associated with human malignancies and neurodevelopmental disorders (NDDs). Somatic SHP2 mutations are associated with many types of cancer including sporadic juvenile myelomonocytic leukemia, acute myeloid leukemia, breast, gastric, lung, melanoma, and colorectal cancers, while heterozygous germline mutations are linked to NDDs such as Noonan and LEOPARD syndromes. Interestingly, different mutations at the same genomic loci of the gene result in different disease phenotypes, either cancer or NDDs. Patients with NDDs have a higher chance of developing cancer, suggesting a linkage between cancer and NDDs, and between their mutations. SHP2 consists of two SH2 domains (nSH2 and cSH2), a phosphatase (PTP) domain, and a flexible C-terminal tail. In autoinhibition, SHP2 is catalytically inactive, adopting a closed conformation in which the DE-loop of nSH2 blocks the catalytic site of PTP. The binding of nSH2 to the phosphotyrosine (pY)-motif relieve the autoinhibition via disruption of the nSH2-PTP interface. To depict mechanism of the mutation-associated activation of SHP2, extensive molecular dynamics simulations were performed for SHP2 protein with the mutations related to cancer and NDDs. The dynamics and conformational alterations of the wild type, cancer mutants (E76K, D61Y, D61V), and NDD mutants (E76D, D61G) of SHP2 were compared. Collective results showed that both cancer and NDD mutations weaken the nSH2-PTP interface, facilitating the SHP2 activation. Interestingly, cancer mutations induce stronger destruction at the nSH2-PTP interface than the NDD mutations. The PTP domain exhibits two pockets, orthosteric and allosteric pockets, at the interface with nSH2. In autoinhibition, the orthosteric pocket provides a binding site for D61 of nSH2, and the allosteric pocket accommodates E76 and A72 of nSH2. During the simulations, we observed that the mutations, E76K and E76D, reduce the interaction in the allosteric pocket, increasing the probability toward the open SHP2 conformation. This gradually weakens the interactions of D61 in the orthosteric pocket, promoting SH2 release and leading to SHP2 activation. The three mutations, D61Y, D61V, and D61G, directly disrupted the interaction in the orthosteric pocket, favoring the substrate binding. However, they do not optimize the nSH2 conformation for the pY binding and unlikely affect the interaction in the allosteric pocket. Our works explain the difference and similarity between the cancer and NDD mutations of SHP2 at the atomic level and provide deeper understanding of the mutation-induced activation of SHP2 for signal transduction through the Ras/MAPK pathway. Citation Format: Yonglan Liu, Mingzhen Zhang, Wengang Zhang, Hyunbum Jang, Ruth Nussinov. The mechanisms of SHP2 activation in cancer and neurodevelopmental disorder [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 873.

Abstract 4012: Preclinical development of SHP2 allosteric inhibitor ICP-189

Abstract Background: SHP2 is a non-receptor protein tyrosine phosphatase which functions as a convergent signaling node downstream of multiple receptor tyrosine kinases (RTKs), and upstream of RAS to promote oncogenic signaling and tumor growth. SHP2 also mediates PD-1 immune blockade of T cells by binding to the immune receptor tyrosine-based inhibitory motif (ITIM) and immune receptor tyrosine-based switch motif (ITSM) of PD-1. SHP2 has long been considered as a plausible oncology drug target not only as an oncoprotein, but also as an important immune modulator. However, for decades, SHP2 was thought to be "undruggable" due to difficulties in targeting its catalytic site. Recent discovery of allosteric site of SHP2 has inspired a novel approach for SHP2 targeting. Here we report the development of ICP-189, which is a potent, highly selective, and orally bioavailable allosteric inhibitor of SHP2, demonstrated robust efficacies in various in vitro and in vivo RAS/MAPK pathway-driven models as mono-therapeutic agent or in combination with other anti-cancer drugs. Results: ICP-189 inhibits phosphatase activity of SHP2 with IC50 values < 5 nM. In a phosphatase profiling assay, ICP-189 efficiently inhibits the catalytic activity of SHP2, with no significant effects on 21 other tested tyrosine and serine/threonine phosphatases, indicating its high selectivity for SHP2. ICP-189 has demonstrated robust in vitro efficacies in a panel of tumor cell lines bearing activated RTK, RAS, NF1 loss-of-function, or BRAF class III mutations. It has also exhibited synergistic tumor killing effects in combination with EGFR, KRASG12C, MEK and CDK4/6 inhibitors. In a series of in vivo efficacy studies, ICP-189 treatment results in robust tumor growth control of MIA-PaCa-2, KYSE-520 and NCI-H358 xenografts. ICP-189 has also shown strong synergies in tumor killing when combined with MEK inhibitor trametinib, KRASG12C inhibitor sotorasib, EGFR inhibitor osimertinib in xenograft models; and when combined with anti-PD-1 antibody in EMT6 syngeneic tumors. The in vivo efficacy of ICP-189 is well accompanied by pharmacodynamic modulations, where ICP-189 exposure levels correlate with the inhibition of p-ERK and DUSP6 mRNA level in tumors. The pharmacokinetic parameters of ICP-189 are overall favorable, with high oral bioavailability. Nonclinical safety evaluations also exhibit acceptable drug tolerability in SD rats and Beagle dogs. Conclusions: ICP-189 is a novel allosteric inhibitor of SHP2 with broad-spectrum anti-tumor activities as a single agent or in combination with other targeted or immune modulating anti-cancer therapeutics. ICP-189 is now in phase I clinical trial in China and United States. Citation Format: Ruixia Liang, Yingxiang Gao, Fangfang Yang, Yingrui Han, Zuopeng Wang, Richard Liu, Charles Ying Wang, Jason Bin Zhang, Xiangyang Chen, Davy Xuesong Ouyang. Preclinical development of SHP2 allosteric inhibitor ICP-189. [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 4012.

Abstract 3919: SHP2-DDX3X complexes contribute to translational control of CD274 mRNA in KRAS-active non-small cell lung cancer

Abstract Background: Immune checkpoint inhibitors (ICIs) have shifted the landscape in management for non-small cell lung cancer (NSCLC) and improve treatment outcomes. However, the 5-year overall survival rate of 23.2% for treatment-naïve patients with late-stage NSCLC on Pembrolizumab therapy can likely be improved. Clinical benefit is correlated with tumoral expression of PD-L1 and mutation burden. Many groups seek to identify other therapeutic targets that could improve response and overall survival. Ongoing work from our group demonstrated that SHP2, a tyrosine phosphatase, can negatively regulate PD-L1 expression in KRAS-active NSCLC, and we seek to understand the mechanism by which this occurs. SHP2 was ectopically expressed in H460 cells, immunoprecipitated and identification of interacting proteins was achieved by mass spectrometry. DDX3X, an RNA helicase, and eukaryotic translation initiation factor 1a (eIF-1a) were identified as high-ranking, potential partners of SHP2. We hypothesized that SHP2 complexes with DDX3X and eIF-1a on newly transcribed CD274 mRNA to negatively regulate PD-L1 expression. Materials and Methods: To confirm SHP2 interactions with DDX3X and eIF-1a, two pull-down assays were performed: 1. bacterially-expressed, his-tagged and immobilized proteins was used as bait for proteins contained in A549 and H460 extracts, and 2. immunoprecipitation of each endogenous protein in A549 and H460 cell extracts. Western blot analysis was performed to evaluate interacting proteins. To determine whether phosphatase activity of SHP2 is required for these interactions, immunoprecipitation was also carried out in the presence of allosteric inhibitors of SHP2 (SHP-099 and RMC-0455). SHP2 ablation was carried out with CRISPR and siRNA to examine PD-L1 expression, also determined by western blot assay. Results: His-tagged DDX3X from bacterial expression systems was able to capture SHP2 protein from both A549 cells and H460 cells, and vice versa with his-tagged SHP2. Immunoprecipitation of endogenous SHP2 was able to co-precipitate DDX3X and vice versa. Phosphatase activity of SHP2 was not required for complex formation nor does it change PD-L1 expression in A549 or H460 cells. Ablation of SHP2 leads to increased PD-L1 expression. Conclusion: A complex containing SHP2 and DDX3X may regulate the translation of CD274 in concert with eukaryotic initiation factors. Other groups have previously reported the control of translation of CD274 mRNA carried out at the 3’ UTR, and we believe this is novel evidence of a translation initiation complex monitoring the expression of CD274. Ribosome footprint and RNA immunoprecipitations are underway to address these questions. Citation Format: Palapoom Wongsaengpiboon. SHP2-DDX3X complexes contribute to translational control of CD274 mRNA in KRAS-active non-small cell lung cancer. [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 3919.

Abstract 3876: Kinetics of RTK activation determine ERK signaling dynamics and resistance to BRAF and MEK inhibitors

Abstract Combination treatment of BRAF inhibitor (BRAFi) and MEK inhibitor (MEKi) produces remarkable response rates and is expected to prevent ERK activation in BRAF-mutant melanoma. However, sporadic ERK reactivation occurs in melanoma models, and efficacy is severely limited by the emergence of drug resistance. The underlying molecular mechanisms that drive ERK reactivation and adaptation to BRAFi/MEKi remain elusive. Here, using single-cell imaging and optogenetic approaches, we show that the strength and duration of receptor tyrosine kinase (RTK) activation determines ERK reactivation and the development of BRAFi/MEKi-resistant cells. Single-cell data reveal that despite global RTK activation by the same external stimuli, only small subsets of melanoma cells induce effective RTK and ERK activation to develop BRAFi/MEKi resistance. Furthermore, by directly controlling RTK activity, we demonstrate that the kinetics of RTK activation determine ERK signaling dynamics and the percentage of drug-resistant cells. While these drug-resistant cells are rare during early stages of drug treatment, they eventually become the dominant population through sustained RTK-mediated ERK activation that drives cell proliferation. Thus, RTK activation in established drug-resistant cells causes effective ERK activation and cell proliferation. Importantly, limiting RTK signaling activation reverses the BRAFi/MEKi-resistant state. We show that targeting SHP2, a mediator of RTK signaling, effectively suppresses RTK-mediated ERK activation and cell proliferation in BRAFi/MEKi-resistant cells. Our results provide mechanistic insights into the contribution of heterogeneity in RTK activation kinetics to ERK reactivation and BRAFi/MEKi resistance, also highlighting SHP2 activity as a promising target to overcome drug resistance in BRAF-mutant melanoma. Citation Format: Sungsoo Kim, Richard Carvajal, Minah Kim, Hee Won Yang. Kinetics of RTK activation determine ERK signaling dynamics and resistance to BRAF and MEK inhibitors. [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 3876.

Discovery of a potent and selective allosteric inhibitor targeting the SHP2 tunnel site for RTK-driven cancer treatment

Src homology 2 domain-containing phosphatase 2 (SHP2) is a cytoplasmic protein tyrosine phosphatase (PTP) that regulates signal transduction of receptor tyrosine kinases (RTKs). Abnormal SHP2 activity is associated with tumorigenesis and metastasis. Because SHP2 contains multiple allosteric sites, identifying inhibitors at specific allosteric binding sites remains challenging. Here, we used structure-based virtual screening to directly search for the SHP2 “tunnel site” allosteric inhibitor. A novel hit (70) was identified as the SHP2 allosteric inhibitor with an IC50 of 10.2 μM against full-length SHP2. Derivatization of hit compound 70 using molecular modeling-guided structure-based modification allowed the discovery of an effective and selective SHP2 inhibitor, compound 129, with 122-fold improved potency compared to the hit. Further studies revealed that 129 effectively inhibited signaling in multiple RTK-driven cancers and RTK inhibitor-resistant cancer cells. Remarkably, 129 was orally bioavailable (F = 55%) and significantly inhibited tumor growth in haematological malignancy. Taken together, compound 129 developed in this study may serve as a promising lead or candidate for cancers bearing RTK oncogenic drivers and SHP2-related diseases.

SH2 Domain-Containing Phosphatase-SHP2 Attenuates Fibrotic Responses through Negative Regulation of Mitochondrial Metabolism in Lung Fibroblasts

We have previously shown that SHP2 downregulation may predispose fibroblasts to differentiate into myofibroblasts and proposed a role for SHP2 downregulation in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Recent data have shown that SHP2 localizes to the mitochondrial intercristae, and its overexpression enhances mitochondrial metabolism leading to oxidative stress and senescence. To determine the effect of SHP2 on fibrotic responses. Primary mouse lung fibroblasts derived from mice carrying a conditional knock-in mutation (D61G/+), rendering the SHP2 catalytic domain constitutively active, had reduced proliferation (1.6-fold, p < 0.05), migration (2-fold, p < 0.05), as well as reduced responsiveness of TGFB-1 induced fibroblasts-to-myofibroblasts differentiation, compared to wild-type ones. Electron microscope analysis revealed that SHP2 D61G/+ mouse lung fibroblasts were characterized by mitochondrial abnormalities, including swollen mitochondria with disrupted electron-lucent cristae and an increased number of autophagosomes compared to wild-type ones. SHP2 D61G/+ MLFs exhibited increased protein levels of autophagy markers, including LC3B-II and p-62, evidence that was confirmed by immunofluorescence analysis. Mitochondrial function analysis revealed that stable (genotype D61G/+) overexpression of SHP2 led to impaired mitochondrial function, as assessed by decreased mitochondrial membrane potential (1.29-fold, p < 0.05), coupling efficiency (1.82 fold, p < 0.05), oxygen consumption rate (1.9-fold, p < 0.05), and increased reactive oxygen species production both at baseline (1.75-fold, p < 0.05) and following H2O2 stimulation (1.63-fold, p < 0.05) compared to wild-type ones (SHP2+/+). SHP2 D61G/+ mouse lung fibroblasts showed enhanced AMPK activity, as well as decreased activation of the mTORC1 signaling pathway, potentially leading to ineffective mitochondrial metabolism and increased autophagy. SHP2 attenuates fibrotic responses in fibroblast cell lines through negative regulation of mitochondrial metabolism and induction of autophagy. SHP2 activation may represent a promising therapeutic strategy for patients with fibrotic lung diseases.

Synthesis and Biological Evaluation of 3-Amino-4,4-Dimethyl Lithocholic Acid Derivatives as Novel, Selective, and Cellularly Active Allosteric SHP1 Activators.

Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1), a non-receptor member of the protein tyrosine phosphatase (PTP) family, negatively regulates several signaling pathways that are responsible for pathological cell processes in cancers. In this study, we report a series of 3-amino-4,4-dimethyl lithocholic acid derivatives as SHP1 activators. The most potent compounds, 5az-ba, showed low micromolar activating effects (EC50: 1.54-2.10 μM) for SHP1, with 7.63-8.79-fold maximum activation and significant selectivity over the closest homologue Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP2) (>32-fold). 5az-ba showed potent anti-tumor effects with IC50 values of 1.65-5.51 μM against leukemia and lung cancer cells. A new allosteric mechanism of SHP1 activation, whereby small molecules bind to a central allosteric pocket and stabilize the active conformation of SHP1, was proposed. The activation mechanism was consistent with the structure-activity relationship (SAR) data. This study demonstrates that 3-amino-4,4-dimethyl lithocholic acid derivatives can be selective SHP1 activators with potent cellular efficacy.

MUC1-C is necessary for SHP2 activation and BRAF inhibitor resistance in BRAF(V600E) mutant colorectal cancer

Colorectal cancers (CRCs) harboring the BRAF(V600E) mutation are associated with aggressive disease and resistance to BRAF inhibitors by feedback activation of the receptor tyrosine kinase (RTK)→RAS→MAPK pathway. The oncogenic MUC1-C protein promotes progression of colitis to CRC; whereas there is no known involvement of MUC1-C in BRAF(V600E) CRCs. The present work demonstrates that MUC1 expression is significantly upregulated in BRAF(V600E) vs wild-type CRCs. We show that BRAF(V600E) CRC cells are dependent on MUC1-C for proliferation and BRAF inhibitor (BRAFi) resistance. Mechanistically, MUC1-C integrates induction of MYC in driving cell cycle progression with activation of the SHP2 phosphotyrosine phosphatase, which enhances RTK-mediated RAS→ERK signaling. We demonstrate that targeting MUC1-C genetically and pharmacologically suppresses (i) activation of MYC, (ii) induction of the NOTCH1 stemness factor, and (iii) the capacity for self-renewal. We also show that MUC1-C associates with SHP2 and is required for SHP2 activation in driving BRAFi-induced feedback of ERK signaling. In this way, targeting MUC1-C in BRAFi-resistant BRAF(V600E) CRC tumors inhibits growth and sensitizes to BRAF inhibition. These findings demonstrate that MUC1-C is a target for the treatment of BRAF(V600E) CRCs and for reversing their resistance to BRAF inhibitors by suppressing the feedback MAPK pathway.

The MYC-regulated lncRNA LNROP (ENSG00000254887) enables MYC-driven cell proliferation by controlling the expression of OCT2

MYC controls most of the non-coding genome. Several long noncoding transcripts were originally identified in the human B cell line P496-3 and then shown to be required for MYC-driven proliferation of Burkitt lymphoma-derived RAMOS cells. In this study, we used RAMOS cells exclusively as a representative of the human B cell lineage. One of the MYC-controlled lncRNAs required for RAMOS cell proliferation is ENSG00000254887 which we will term LNROP (long non-coding regulator of POU2F2). In the genome, LNROP is located in close proximity of POU2F2, the gene encoding OCT2. OCT2 is a transcription factor with important roles in sustaining the proliferation of human B cells. Here we show that LNROP is a nuclear RNA and a direct target of MYC. Downregulation of LNROP attenuates the expression of OCT2. This effect of LNROP on the expression of OCT2 is unidirectional as downregulation of OCT2 does not alter the expression of LNROP. Our data suggest that LNROP is a cis-acting regulator of OCT2. To illustrate the downstream reach of LNROP, we chose a prominent target of OCT2, the tyrosine phosphatase SHP-1. Downregulation of OCT2 elevates the expression of SHP-1. Our data suggest the following path of interactions: LNROP enables the proliferation of B cells by positively and unidirectionally regulating the growth-stimulatory transcription factor OCT2. In actively proliferating B cells, OCT2 attenuates the expression and anti-proliferative activity of SHP-1.

Genome-wide CRISPR/Cas9 screens reveal shared and cell-specific mechanisms of resistance to SHP2 inhibition.

SHP2 (PTPN11) acts upstream of SOS1/2 to enable RAS activation. Allosteric SHP2 inhibitors (SHP2i) in the clinic prevent SHP2 activation, block proliferation of RTK- or cycling RAS mutant-driven cancers, and overcome "adaptive resistance." To identify SHP2i resistance mechanisms, we performed genome-wide CRISPR/Cas9 knockout screens on two SHP2i-sensitive cell lines, recovering genes expected to cause resistance (NF1, PTEN, CDKN1B, LZTR1, and RASA2) and novel targets (INPPL1, MAP4K5, epigenetic modifiers). We screened 14 additional lines with a focused CRISPR library targeting common "hits" from the genome-wide screens. LZTR1 deletion conferred resistance in 12/14 lines, followed by MAP4K5 (8/14), SPRED2/STK40 (6/14), and INPPL1 (5/14). INPPL1, MAP4K5, or LZTR1 deletion reactivated ERK signaling. INPPL1-mediated sensitization to SHP2i required its NPXY motif but not lipid phosphatase activity. MAP4K5 acted upstream of MEK through a kinase-dependent target(s); LZTR1 had cell-dependent effects on RIT and RAS stability. INPPL1, MAP4K5, or LZTR1 deletion also conferred SHP2i resistance in vivo. Defining the SHP2i resistance landscape could suggest effective combination approaches.