As mutually exclusive catalytic ATPase subunits of the SWI/SNF chromatin remodeling complex, SMARCA2 and SMARCA4 play crucial roles in regulating gene transcription. Studies have revealed that SMARCA4-deficient cells exquisitely depend on SMARCA2 for survival, suggesting SMARCA2 is a promising synthetic lethal target in SMARCA4-deficient cancers. Herein, we reported the design, synthesis, and biological evaluation of a series of novel proteolysis targeting chimeras (PROTACs) of SMARCA2 bearing a novel furo[3,2-c]pyridazine scaffold. Among these compounds, compound 26 displayed an excellent SMARCA2 degradation efficiency with a DC50 value of 51 nM and potently inhibited SMARCA4-deficient cancer cell growth. Compared with AU-15330, which has comparable degradation activity towards SMARCA2/4 (DC50: 42 nM vs 41 nM), compound 26 achieved a 5-fold selectivity towards SMARCA2. In NCI-H1944 xenograft model, 26 significantly reduced SMARCA2 protein levels in tumor tissue and inhibited tumor growth without obvious adverse events, indicating that compound 26 is a promising lead compound for further evaluation as potential treatment of SMARCA4-deficient cancers.

Aberrant activation of PI3K signaling is frequently observed in lung squamous cell carcinoma (LUSC) and is strongly associated with metastasis in advanced-stage patients, but the therapeutic efficacy of PI3K inhibitors and underlying mechanisms in LUSC remain poorly defined. CYH33 is a highly selective PI3Kα inhibitor, which is in phase I/II clinical trials for the therapy of advanced solid tumors including LUSC. In this study, we investigated the efficacy of CYH33 against metastatic LUSC. We showed that CYH33 dose-dependently suppressed the motility of LUSC cells by blocking PI3K signaling and disrupting cytoskeletal structure. Oral administration of CYH33 significantly attenuated the metastasis of orthotopically implanted xenografts derived from LUSC SK-MES-1 cells. RNA-seq and GO enrichment analysis revealed that CYH33 treatment resulted in decreased infiltration of cancer-associated fibroblasts (CAFs) in primary tumors. We demonstrated that CAFs promoted the migration of SK-MES-1 cells by secreting the pro-migratory factors and activating PI3K signaling in tumor cells, which was blocked by CYH33. Moreover, CYH33 concurrently suppressed the trans-differentiation and proliferation of CAFs, thereby reducing the secretion of hepatocyte growth factor (HGF), which likely contributed to its anti-metastatic effect. Consistently, co-inoculation of SK-MES-1 cells with fibroblasts significantly potentiated tumor metastasis in nude mice, whereas CYH33 treatment robustly suppressed this process, accompanied with reduced expression of α-SMA and HGF as well as epithelial-mesenchymal transition (EMT) signature in primary tumor. Furthermore, CYH33 possessed potent activity against the growth of LUSC with hyperactivated PI3K signaling. Collectively, the dual-targeting of CYH33 that directly blocked PI3Kα in tumor cells and disrupted CAF-mediated pro-metastatic signaling supported PI3Kα inhibitors as a potential therapeutic approach for advanced LUSC.

Clear cell renal cell carcinoma (ccRCC), a kidney cancer subtype, is characterized by its aggressive nature and limited treatment options, leading to a poor prognosis. We observed elevated levels of CSF1R and PIK3CD in ccRCC tissues. A new CSF1R/PI3Kδ dual inhibitor, JMC14, greatly reduced the growth of xenografts originating from ccRCC A498 cells despite showing only moderate activity against cell proliferation in vitro. Single-cell RNA sequencing of A498 tumors demonstrated that JMC14 altered the tumor microenvironment (TME) by decreasing the presence of immunosuppressive macrophages. JMC14 modulated macrophage polarization towards the M1-like phenotype and inhibited M2 tumor-associated macrophage (TAM)-mediated tumor angiogenesis by decreasing the secretion of IL-8 and VEGF, which might be associated with blocking the STAT3 and NF-κB pathways in macrophages. JMC14 significantly impeded the growth of xenografts derived from ccRCC 786-O cells and patient samples while also decreasing M2 macrophage infiltration and attenuating angiogenesis. Taken together, simultaneously targeting CSF1R and PIK3CD displayed significant efficacy in ccRCC and inhibited tumor angiogenesis via reshaping the TME, providing a promising rationale for the therapy of ccRCC.

Organic ylides, defined by adjacent oppositely charged centers, are virtually absent from the pharmacopeia due to long-standing concerns over instability and reactivity under physiological conditions. Within this class, N-iminopyridinium ylides have remained unexplored. Herein, we report an efficient two-step synthesis of tetracyclic compounds incorporating this scaffold and demonstrate their function as chemically stable pharmacophores for targeted protein degradation. Lead compound 4p exhibited potent binding to the bromodomains of SMARCA2 and SMARCA4 while demonstrating remarkable stability in aqueous buffer and cell culture media, along with favorable cell permeability. Computational studies, together with head-to-head comparison against the corresponding amide analog, confirmed that the ylide moiety is indispensable for activity. Building on this scaffold, PROTAC 14 induced robust degradation of SMARCA2 and PBRM1 in SMARCA4 mutant cancer cells, suppressed cell proliferation, displayed favorable pharmacokinetics in rodents, and achieved significant antitumor efficacy in a xenograft model. Collectively, these findings establish the N-iminopyridinium ylide as a chemically stable, biocompatible, and pharmacologically tractable scaffold for designing bioactive ligands and degraders. More broadly, they position organic ylides as a previously untapped class of pharmacophores for drug discovery, thereby expanding the chemical space for targeted protein degradation.

ENPP1, a transmembrane glycoprotein overexpressed in various cancers, has become a promising target for tumor immunotherapy. Several ENPP1 inhibitors have been reported, but only a few have been validated in vivo. Herein, based on the reported inhibitors 3 and 6, we carried out a structural optimization by designing a variety of 8-methoxyquinazoline and its equivalent 8-methoxy-3-cyano-quinoline derivatives featuring bridged- or spirobicycles as the linker. Compound 30 was identified as a promising ENPP1 inhibitor. This compound exhibited IC50 values of 8.05 nM against ENPP1 and 1.53 nM in MDA-MB-231 cells with no significant inhibitory effects against both hERG and a panel of 97 kinases. It effectively activated the intracellular STING pathway by inhibiting cGAMP degradation. In the murine CT-26 tumor model, 30 inhibited tumor growth with increased immune cell infiltration in the tumor microenvironment and enhanced type I interferon responses. Meanwhile, compound 30 synergically enhanced the antitumor efficacy of anti-PD-L1 antibody.

Hematopoietic progenitor kinase 1 (HPK1) has emerged as a promising target for cancer immunotherapy due to its critical role as a negative regulator of T cell receptor (TCR) signaling. Despite this potential, no HPK1 inhibitors have been approved for cancer treatment, underscoring the need for structurally novel inhibitors. Herein, we describe the design, synthesis and biological evaluation of a series of potent HPK1 inhibitors based on our previously identified hit 9. Among them, compound 24 demonstrated strong HPK1 inhibition (IC50 of 10.1 nM) and effectively suppressed phosphorylation of the downstream protein SLP76. Notably, compound 24 exhibited enhanced potency in promoting IL-2 secretion in Jurkat T cells, reduced cellular toxicity, and improved liver microsomal stability compared to hit 9. Overall, this study provides a promising lead compound for further optimization as a candidate for cancer immunotherapy.

The hyperactivation of the PI3K pathway in head and neck squamous cell carcinoma (HNSCC) suggests that targeting PI3K is a potential therapeutic strategy. CYH33 is a novel PI3Kα-selective inhibitor discovered by our group, which is currently undergoing a phase I clinical trial (NCT03544905) for the treatment of advanced solid tumors including HNSCC. However, there is an urgent need to elucidate its mechanism of action and improve its efficacy against HNSCC. In this study, we found that CYH33 displayed promising but variable therapeutic activity against HNSCC. Inhibition of PI3K/Akt pathway by CYH33 was not sufficient for its activity against HNSCC. Tandem-Mass-Tag (TMT) phosphoproteomics were performed to reveal comprehensive regulation of kinome by CYH33. Particularly, attenuation of Erk phosphorylation was associated with the sensitivity of HNSCC cells to CYH33. Mechanistically, inhibition of PI3K by CYH33 blocked the PIP3 production and attenuated the membrane localization and phosphorylation of GAB1, resulting in reduced Erk phosphorylation and ultimately inhibition of cell proliferation in sensitive HNSCC cells. Meanwhile, activation of EGFR induced GAB1 phosphorylation independent of PI3K in HNSCC cells. Concurrent inhibition of EGFR synergistically potentiated the activity of CYH33 against HNSCC. These findings revealed the insight mechanism of CYH33 against HNSCC and provided rational combination regimen for HNSCC treatment.

Hematopoietic progenitor kinase 1 (HPK1) functions as a key negative regulator of T cell receptor signaling and has been considered a potential target for cancer immunotherapy. Despite great progress in developing HPK1 inhibitors, no small-molecule inhibitors have been approved for cancer treatment to date. Herein, we describe the design and synthesis of a novel series of macrocyclic 2,4-diaminopyrimidine derivatives as HPK1 inhibitors. Among these, the representative compound 21 exhibited potent HPK1 inhibition with an IC50 value of 1.0 nM in an ADP-Glo assay. Furthermore, compound 21 effectively inhibited phosphorylation of the downstream adaptor protein SLP76 and enhanced IL-2 secretion in human Jurkat T cells. Taken together, this study further validates macrocyclization as an effective strategy for designing HPK1 inhibitors with innovative scaffolds and offers compound 21 as a structurally novel lead compound for the development of HPK1 inhibitors.

PI3Kδ, predominantly expressed in immune cells and markedly dysregulated in B-cell malignancies, emerges as a promising and well-validated therapeutic target in hematologic cancers. Meanwhile, CSF1R regulates the formation and polarization of tumor-associated macrophages (TAMs), facilitating immune suppression and tumor progression in various solid tumors. Although targeting PI3Kδ or CSF1R has shown promise, the clinical application is often constrained by off-target effects, toxicity, and limited efficacy, particularly in solid malignancies. In this study, we identified JMC14, a novel dual inhibitor targeting PI3Kδ and CSF1R with a distinct structure and favorable selectivity among human kinome, yielding IC50 values of 12 nM against PI3Kδ and 143 nM against CSF1R, respectively. JMC14 preferentially inhibited PI3Kδ-mediated signaling at the cellular level and exhibited robust antiproliferative activity across 10 lines of diffuse large B-cell lymphoma (DLBCL) cells, outperforming the approved PI3Kδ inhibitor idelalisib. Notably, its efficacy negatively correlated with the PI3Kα expression among the cell lines tested, suggesting a compensatory pathway mediated by PI3Kα. Daily oral administration of JMC14 (10, 30, or 100 mg/kg, for 21 days) dose-dependently suppressed tumor progression in xenografts derived from TMD8 cells and DLBCL patients, accompanied by good tolerance. Additionally, M-NFS-60 myeloid leukemia cells, which are dependent on the CSF-1-CSF1R axis for survival and proliferation, were effectively inhibited by JMC14 both in vitro and in vivo, further validating its inhibitory activity targeting CSF1R. Furthermore, JMC14 demonstrated potent antitumor activity in murine triple-negative breast cancer (TNBC), which was associated with its activity to reshape the immune microenvironment by reducing M2-like TAMs, enhancing CD8+ T cell infiltration. Collectively, these findings establish JMC14 as a potent dual PI3Kδ/CSF1R inhibitor with remarkable efficacy against both hematologic and solid malignancies with hyperactivation of PI3Kδ and/or CSF1R, highlighting the potential of JMC14 as a useful probe to dissect the interaction of PI3Kδ and CSF1R in tumor progression and immune reprogramming.

SWI/SNF chromatin remodeling complexes are essential epigenetic regulators that control chromatin accessibility and transcriptional programs. Alterations in SWI/SNF components are common across a wide spectrum of human cancers, driving tumorigenesis through diverse mechanisms. Increasing insights into the oncogenic roles of aberrant SWI/SNF complexes have spurred the development of novel therapeutic strategies. In this review, we integrate large-scale cancer genomic data towards understanding tumorigenesis driven by alterations in subunits of SWI/SNF complexes. We also evaluate strategies exploiting vulnerabilities in SWI/SNF-mutant cancers, including direct targeting of residual complex components and unique dependencies in critical cellular processes. Among them, one drug has been approved, and several others are in clinical trials.

Genetic mutations in components of the Hippo pathway frequently lead to the aberrant activation of TEADs, which is often associated with cancer. Consequently, TEADs have been actively pursued as therapeutic targets for diseases driven by TEAD overactivation. In this study, we report two series of TEAD PROTACs based on CRBN binders and VHL binders. Both series yielded potent TEAD degraders, including 19 and 40 (H122), which induced TEAD1 degradation with DC50 < 10 nM. Mechanistic studies demonstrated that the degradation of TEAD1 induced by 40 relied on CRBN binding, TEAD1 binding, E3 ligase activity, and a functional proteasome. RNA-seq analyses indicated that 40 significantly downregulated the expression of Myc target genes, as highlighted by GSEA analysis. More importantly, 40 exhibited robust antitumor efficacy in the MSTO-211H mouse xenograft model. Collectively, our results suggest that TEAD PROTACs have therapeutic potential for the treatment of cancers associated with TEAD overactivation.

Ectonucleotide pyrophosphatase/ phosphodiesterase 1 (ENPP1) is an extracellular enzyme responsible for hydrolyzing cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), the endogenous agonist for the stimulator of interferon genes (STING) pathway. Inhibition of ENPP1 can trigger STING and promote antitumor immunity, offering an attractive therapeutic target for cancer immunotherapy. Despite progress in the discovery of ENPP1 inhibitors, the diversity in chemical structures and the efficacy of the agents are far from desirable, emphasizing the demand for novel inhibitors. Herein, we describe the design, synthesis, and biological evaluation of a series of ENPP1 inhibitors based on the pyrido[2,3-d]pyrimidin-7-one scaffold. Optimization efforts led to compound 31 with significant potency in both ENPP1 inhibition and STING pathway stimulation in vitro. Notably, 31 demonstrated in vivo efficacy in a syngeneic 4T1 mouse triple negative breast cancer model. These findings provide a promising lead compound with a novel scaffold for further drug development in cancer immunotherapy.

Cytosolic double-stranded DNA (dsDNA) is frequently accumulated in cancer cells due to chromosomal instability or exogenous stimulation. Cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, which is activated upon binding to dsDNA to synthesize the crucial second messenger 2’3’-cyclic GMP-AMP (2’3’-cGAMP) that in turn triggers stimulator of interferon genes (STING) signaling. The canonical role of cGAS-cGAMP-STING pathway is essential for innate immunity and viral defense. Recent emerging evidence indicates that 2’3’-cGAMP plays an important role in cancer progression via cell autonomous and non-autonomous mechanisms. Beyond its role as an intracellular messenger to activate STING signaling in tumor cells, 2’3’-cGAMP also serves as an immunotransmitter produced by cancer cells to modulate the functions of non-tumor cells especially immune cells in the tumor microenvironment by activating STING signaling. In this review, we summarize the synthesis, transmission, and degradation of 2’3’-cGAMP as well as the dual functions of 2’3’-cGAMP in a STING-dependent manner. Additionally, we discuss the potential therapeutic strategies that harness the cGAMP-mediated antitumor response for cancer therapy.

Soil surface roughness (SSR) is an important factor affecting soil erosion and soil nutrient transport. Human tillage leads to increased instability in SSR, and the characteristics of SSR caused by different tillage practices await further study. This research utilizes terrestrial laser scanning (TLS) to measure the SSR of six farmland plots (25 m × 25 m) and analyzes the characteristics of SSR under different tillage practices (ploughing, harrowing, ridging, crusting, etc.). The study results show: 1) Different agricultural tillage practices lead to significant differences in SSR. The ploughed and harrowed plot correspond to the maximum (2.49 cm) and minimum (1.5 cm) root mean square height (RMSH), respectively. Correlation length (CL) is more affected by different tillage practices than RMSH. The difference in CL between the ridged and harrowed plot is 2.6 times. 2) Ridging and crusting caused significant directional variation in SSR. The SSR anisotropy of the harrowed plot can be disregarded. 3) Under the condition of measuring soil profile in 12 directions and randomly sampling 70 times in each direction, the profile length must be at least 3 m to ensure that the measurement error of SSR is better than 5% compared to the “true” value. TLS can measure two-dimensional SSR. Therefore, it is only necessary to ensure that the measurement range is at least 3 m × 3 m. The study results provide a reference for the high-precision measurement of SSR (RMSH and CL) under different agricultural tillage practices.

In Northeast China, transplanted rice cultivation has been adopted to extend the rice growing season and boost yields, responding to the limitations of the cumulative temperature zone and high food demand. However, direct-seeded rice offers advantages in water conservation and labour efficiency. The precise and timely monitoring of the distribution of different rice planting types is key to ensuring food security and promoting sustainable regional development. This study explores the feasibility of mapping various rice planting types using only early-stage satellite data from the rice growing season. We focused on Daxing Farm in Fujin City, Jiamusi City, Heilongjiang Province, for cropland plot extraction using Planet satellite imagery. Utilizing Sentinel-2 satellite imagery, we analysed the differences in rice’s modified normalized difference water index (MNDWI) during specific phenological periods. A multitemporal Gaussian mixture model (GMM) was developed, integrated with the maximum expectation algorithm, to produce binarized classification outcomes. These results were employed to detect surface changes and map the corresponding rice cultivation types. The probability of various rice cultivation types within arable plots was quantified, yielding a plot-level rice-cultivation-type mapping product. The mapping achieved an overall accuracy of 91.46% in classifying rice planting types, with a Kappa coefficient of 0.89. The area extraction based on arable land parcels showed a higher R2 by 0.1109 compared to pixel-based area extraction and a lower RMSE by 0.468, indicating more accurate results aligned with real statistics and surveys, thus validating our study’s method. This approach, not requiring labelled samples or many predefined parameters, offers a new method for rapid and feasible mapping, especially suitable for direct-seeded rice areas in Northeast China. It fills the gap in mapping rice distribution for different planting types, supporting water management in rice fields and policies for planting-method changes.

Contour farming technology plays a key role in reducing soil erosion,enhancing water use efficiency,and fostering sustain-able agricultural development.Despite being a straightforward yet efficacious farming technique,it has not seen widespread implement-ation in China.Considering the deteriorating quality of arable lands in the Black Soil Region of Northeast China(BSR-NEC),it is ne-cessary to investigate spatial patterns and identify suitable areas for contour farming in this region.To achieve this objective,spatial autocorrelation and grouping analysis methods were employed to classify the land into four categories of suitability for contour farming:highly suitable,moderately suitable,generally suitable,and unsuitable.The results reveal that:1)the contour farming suitable area in BSR-NEC covers 89 861.32 km2,accounting for 21.59％of arable land as of 2020.Heilongjiang Province owns the largest suitable area of 32 853.68 km2,and Inner Mongolia has the highest proportion of 28.89％.2)In terms of the spatial distribution,regions with higher suitability for contour farming are concentrated in the Da Hinggan Mountains region,particularly Nenjiang City(Heilongjiang Province),which has the highest area of 2593.07 km2.Areas with a high proportion of suitable arable lands for contour farming are mainly found in the Da Hinggan Mountains and Changbai Mountains regions,with Ergun City(Inner Mongolia)having the highest pro-portion at 47.2％.Regions with higher suitability and proportion are concentrated in the Da Hinggan Mountains region,primarily cover-ing the Inner Mongolia and Heilongjiang.3)Regarding spatial clustering,both the area and proportion of suitable contour farming areas exhibit noticeable clustering effects,though not entirely consistent.4)Group analysis results designate 148 counties in BSR-NEC as highly suitable areas,predominantly located in the Changbai Mountains region,Liaodong Peninsula,Hulun Buir Plateau,and the north and south regions of the Da Hinggan Mountains.The zoning of suitable areas for contour farming in BSR-NEC informs the strategic de-velopment of policies and measures,allowing for the implementation of targeted policies in distinct areas suitable for contour farming.This provides a valuable reference for promoting contour farming technology more effectively and efficiently.re effectively and effi-ciently.

Farmland shelterbelts are aimed at farmland protection and productivity improvement, environmental protection and ecological balance, as well as land use planning and management. Farmland shelterbelts play a vital role in determining the structural integrity and overall effectiveness of farmland, and assessing the dynamic changes within these protective forests accurately and swiftly is essential to maintaining their protective functions as well as for policy formulation and effectiveness evaluation in relevant departments. Traditional methods for extracting farmland shelterbelt information have faced significant challenges due to the large workload required and the inconsistencies in the accuracy of existing methods. For example, the existing vegetation index extraction methods often have significant errors, which remain unresolved. Therefore, developing a more efficient extraction method with greater accuracy is imperative. This study focused on Youyi Farm in Heilongjiang Province, China, utilizing satellite data with spatial resolutions ranging from 0.8 m (GF-7) to 30 m (Landsat). By taking into account the growth cycles of farmland shelterbelts and variations in crop types, the optimal temporal window for extraction is identified based on phenological analysis. The study introduced a new index—the Re-Modified Anthocyanin Reflectance Index (RMARI)—which is an improvement on existing vegetation indexes, such as the NDVI and the improved original ARI. Both the accuracy and extraction results showed significant improvements, and the feasibility of the RMARI was confirmed. The study proposed four extraction schemes for farmland shelterbelts: (1) spectral feature extraction, (2) extraction using vegetation indexes, (3) random forest extraction, and (4) RF combined with characteristic index bands. The extraction process was implemented on the GEE platform, and results from different spatial resolutions were compared. Results showed that (1) the bare soil period in May is the optimal time period for extracting farmland shelterbelts; (2) the RF method combined with characteristic index bands produces the best extraction results, effectively distinguishing shelterbelts from other land features; (3) the RMARI reduces background noise more effectively than the NDVI and ARI, resulting in more comprehensive extraction outcomes; and (4) among the satellite images analyzed—GF-7, Planet, Sentinel-2, and Landsat OLI 8—GF-7 achieves the highest extraction accuracy (with a Kappa coefficient of 0.95 and an OA of 0.97), providing the most detailed textural information. However, comprehensive analysis suggests that Sentinel-2 is more suitable for large-scale farmland shelterbelt information extraction. This study provides new approaches and technical support for periodic dynamic forestry surveys, providing valuable reference points for agricultural ecological research.

Supplementary Table 1 from Nonclassic Functions of Human Topoisomerase I: Genome-Wide and Pharmacologic Analyses

Protein phosphatase 1 regulatory subunit 15A (PPP1R15A) is an important factor in the integrated stress response (ISR) in mammals and may play a crucial role in tumorigenesis. In our studies, we found an inhibitor of PPP1R15A, Sephin1, plays a protumorigenic role in mouse tumor models. By analyzing the single-cell transcriptome data of the mouse tumor models, we found that in C57BL/6 mice, Sephin1 treatment could lead to higher levels of ISR activity and lower levels of antitumor immune activities. Specifically, Sephin1 treatment caused reductions in antitumor immune cell types and lower expression levels of cytotoxicity-related genes. In addition, T cell receptor (TCR) repertoire analysis demonstrated that the clonal expansion of tumor-specific T cells was inhibited by Sephin1. A special TCR + macrophage subtype in tumor was identified to be significantly depleted upon Sephin1 treatment, implying its key antitumor role. These results suggest that PPP1R15A has the potential to be an effective target for tumor therapy.

Phosphatidylinositol 3-kinase alpha (PI3Kα) inhibitors are currently evaluated for the therapy of esophageal squamous cell carcinoma (ESCC). It is of great importance to identify potential biomarkers to predict or monitor the efficacy of PI3Kα inhibitors in an aim to improve the clinical responsive rate in ESCC. Here, ESCC PDXs with CCND1 amplification were found to be more sensitive to CYH33, a novel PI3Kα-selective inhibitor currently in clinical trials for the treatment of advanced solid tumors including ESCC. Elevated level of cyclin D1, p21 and Rb was found in CYH33-sensitive ESCC cells compared to those in resistant cells. CYH33 significantly arrested sensitive cells but not resistant cells at G1 phase, which was associated with accumulation of p21 and suppression of Rb phosphorylation by CDK4/6 and CDK2. Hypo-phosphorylation of Rb attenuated the transcriptional activation of SKP2 by E2F1, which in turn hindered SKP2-mediated degradation of p21 and reinforced accumulation of p21. Moreover, CDK4/6 inhibitors sensitized resistant ESCC cells and PDXs to CYH33. These findings provided mechanistic rationale to evaluate PI3Kα inhibitors in ESCC patients harboring amplified CCND1 and the combined regimen with CDK4/6 inhibitors in ESCC with proficient Rb.