Prediction of cell cycle distribution after drug exposure by high content imaging analysis using low-toxic DNA staining dye.

Interference in cell cycle progression has been noted as one of the important properties of anticancer drugs. In this study, we developed the cell cycle prediction model using high-content imaging data of recipient cells after drug exposure and DNA-staining with a low-toxic DNA dye, SiR-DNA. For this purpose, we exploited HeLa and MCF7 cells introduced with a fluorescent ubiquitination-based cell cycle indicator (Fucci). Fucci-expressing cancer cells were subjected to high-content imaging analysis using OperettaCLS after 36-h exposure to anticancer drugs; the nuclei were segmented, and the morphological and intensity properties of each nucleus characterized by SiR-DNA staining were calculated using imaging analysis software, Harmony. For the use of training, we classified cells into each phase of the cell cycle using the Fucci system. Training data (n = 7500) and validation data (n = 2500) were randomly sampled and the binary classification prediction models for G1, early S, and S/G2/M phases of the cell cycle were developed using four supervised machine learning algorithms. We selected random forest as the model with the best performance through 10-fold cross-validation; the accuracy rate was approximately 75%-87%. Regarding feature importance, variables expected to be biologically related to the cell cycle, for example, signal intensity and nuclear size, were highly ranked, suggesting the validity of the model. These results showed that the cell cycle can be predicted in cancer cells by simply exploiting the current prediction model using fluorescent images of DNA-staining dye, and the model could be applied for the use of future ex vivo drug sensitivity diagnosis.

A novel pan-PI3K inhibitor KTC1101 synergizes with anti-PD-1 therapy by targeting tumor suppression and immune activation.

BACKGROUND: Phosphoinositide 3-kinases (PI3Ks) are critical regulators of diverse cellular functions and have emerged as promising targets in cancer therapy. Despite significant progress, existing PI3K inhibitors encounter various challenges such as suboptimal bioavailability, potential off-target effects, restricted therapeutic indices, and cancer-acquired resistance. Hence, novel inhibitors that overcome some of these challenges are needed. Here, we describe the characterization of KTC1101, a novel pan-PI3K inhibitor that simultaneously targets tumor cell proliferation and the tumor microenvironment. Our studies demonstrate that KTC1101 significantly increases the anti-PD-1 efficacy in multiple pre-clinical mouse models. METHODS: KTC1101 was synthesized and characterized employing chemical synthesis, molecular modeling, Nuclear Magnetic Resonance (NMR), and mass spectrometry. Its target specificity was confirmed through the kinase assay, JFCR39 COMPARE analysis, and RNA-Seq analysis. Metabolic stability was verified via liver microsome and plasma assays, pharmacokinetics determined by LC-MS/MS, and safety profile established through acute toxicity assays to determine the LD50. The antiproliferative effects of KTC1101 were evaluated in a panel of cancer cell lines and further validated in diverse BALB/c nude mouse xenograft, NSG mouse xenograft and syngeneic mouse models. The KTC1101 treatment effect on the immune response was assessed through comprehensive RNA-Seq, flow cytometry, and immunohistochemistry, with molecular pathways investigated via Western blot, ELISA, and qRT-PCR. RESULTS: KTC1101 demonstrated strong inhibition of cancer cell growth in vitro and significantly impeded tumor progression in vivo. It effectively modulated the Tumor Microenvironment (TME), characterized by increased infiltration of CD8+ T cells and innate immune cells. An intermittent dosing regimen of KTC1101 enhanced these effects. Notably, KTC1101 synergized with anti-PD-1 therapy, significantly boosting antitumor immunity and extending survival in preclinical models. CONCLUSION: KTC1101's dual mechanism of action-directly inhibiting tumor cell growth and dynamically enhancing the immune response- represents a significant advancement in cancer treatment strategies. These findings support incorporating KTC1101 into future oncologic regimens to improve the efficacy of immunotherapy combinations.

Identification of a dihydroorotate dehydrogenase inhibitor that inhibits cancer cell growth by proteomic profiling.

Dihydroorotate dehydrogenase (DHODH) is a central enzyme of the de novo pyrimidine biosynthesis pathway and is a promising drug target for the treatment of cancer and autoimmune diseases. This study presents the identification of a potent DHODH inhibitor by proteomic profiling. Cell-based screening revealed that NPD723, which is reduced to H-006 in cells, strongly induces myeloid differentiation and inhibits cell growth in HL-60 cells. H-006 also suppressed the growth of various cancer cells. Proteomic profiling of NPD723-treated cells in ChemProteoBase showed that NPD723 was clustered with DHODH inhibitors. H-006 potently inhibited human DHODH activity in vitro, whereas NPD723 was approximately 400 times less active than H-006. H-006-induced cell death was rescued by the addition of the DHODH product orotic acid. Moreover, metabolome analysis revealed that H-006 treatment promotes marked accumulation of the DHODH substrate dihydroorotic acid. These results suggest that NPD723 is reduced in cells to its active metabolite H-006, which then targets DHODH and suppresses cancer cell growth. Thus, H-006-related drugs represent a potentially powerful treatment for cancer and other diseases.

Invivo anti-cancer activity of 10-methyl-aplog-1, a simplified analog of aplysiatoxin, and its possible signaling pathway associated with G1 arrest.

Naturally occurring protein kinase C (PKC) activators such as phorbol esters, teleocidins, and aplysiatoxins, have the potential to become anti-cancer agents, since they are anti-proliferative against specific cancer cell lines in vitro. However, their potent tumor-promoting and proinflammatory activities have hampered their clinical uses. Recently, we developed 10-methyl-aplog-1 (1), a simplified analog of tumor-promoting debromoaplysiatoxin (DAT), which retained anti-proliferative activity comparable to DAT, but induced neither tumorigenesis nor inflammation on mouse skin. Our previous study suggested that PKCα and δ were involved in the cell line-selective anti-proliferative activity of 1, but the downstream signaling of PKC isozymes remained unknown. In this study, we confirmed that 1 inhibited the growth of three aplog-sensitive cancer cell lines (NCI-H460, HCC-2998, and HBC-4) without severe side effects in mice xenograft models. In addition, in vitro analysis using A549, one of the aplog-sensitive cell lines in vitro, revealed that PKCα induced PP2A-mediated attenuation of the Akt/S6 signaling axis. Since S6 inhibition in A549 was reported to result in G1 arrest, this pathway could be involved in the PKCα-dependent anti-proliferative activity of 1.

Subtype-selective induction of apoptosis in translocation-related sarcoma cells induced by PUMA and BIM upon treatment with pan-PI3K inhibitors.

Translocation-related sarcomas (TRSs) harbor an oncogenic fusion gene generated by chromosome translocation and account for approximately one-third of all sarcomas; however, effective targeted therapies have yet to be established. We previously reported that a pan-phosphatidylinositol 3-kinase (PI3K) inhibitor, ZSTK474, was effective for the treatment of sarcomas in a phase I clinical trial. We also demonstrated the efficacy of ZSTK474 in a preclinical model, particularly in cell lines from synovial sarcoma (SS), Ewing's sarcoma (ES) and alveolar rhabdomyosarcoma (ARMS), all of which harbor chromosomal translocations. ZSTK474 selectively induced apoptosis in all these sarcoma cell lines, although the precise mechanism underlying the induction of apoptosis remained unclear. In the present study, we aimed to determine the antitumor effect of PI3K inhibitors, particularly with regards to the induction of apoptosis, against various TRS subtypes using cell lines and patient-derived cells (PDCs). All of the cell lines derived from SS (six), ES (two) and ARMS (one) underwent apoptosis accompanied by the cleavage of poly-(ADP-ribose) polymerase (PARP) and the loss of mitochondrial membrane potential. We also observed apoptotic progression in PDCs from SS, ES and clear cell sarcoma (CCS). Transcriptional analyses revealed that PI3K inhibitors triggered the induction of PUMA and BIM and the knockdown of these genes by RNA interference efficiently suppressed apoptosis, suggesting their functional involvement in the progression of apoptosis. In contrast, TRS-derived cell lines/PDCs from alveolar soft part sarcoma (ASPS), CIC-DUX4 sarcoma and dermatofibrosarcoma protuberans failed to undergo apoptosis nor induce PUMA and BIM expression, as well as cell lines derived from non-TRSs and carcinomas. Thus, we conclude that PI3K inhibitors induce apoptosis in selective TRSs such as ES and SS via the induction of PUMA and BIM and the subsequent loss of mitochondrial membrane potential. This represents proof of concept for PI3K-targeted therapy, particularly such TRS patients.

Discovery of novel DNA-damaging agents through phenotypic screening for DNA double-strand break.

DNA double-strand breaks (DSBs) seriously damage DNA and promote genomic instability that can lead to cell death. They are the source of conditions such as carcinogenesis and aging, but also have important applications in cancer therapy. Therefore, rapid detection and quantification of DSBs in cells are necessary for identifying carcinogenic and anticancer factors. In this study, we detected DSBs using a flow cytometry-based high-throughput method to analyze γH2AX intensity. We screened a chemical library containing 9600 compounds and detected multiple DNA-damaging compounds, although we could not identify mechanisms of action through this procedure. Thus, we also profiled a representative compound with the highest DSB potential, DNA-damaging agent-1 (DDA-1), using a bioinformatics-based method we termed "molecular profiling." Prediction and verification analysis revealed DDA-1 as a potential inhibitor of topoisomerase IIα, different from known inhibitors such as etoposide and doxorubicin. Additional investigation of DDA-1 analogs and xenograft models suggested that DDA-1 is a potential anticancer drug. In conclusion, our findings established that combining high-throughput DSB detection and molecular profiling to undertake phenotypic analysis is a viable method for efficient identification of novel DNA-damaging compounds for clinical applications.

Synthesis of Acetogenin Analogs Comprising Pyrimidine Moieties Linked by Amine Bonds and Their Inhibitory Activity against Human Cancer Cell Lines.

Here, we synthesized three acetogenin analogs containing pyrimidine moieties linked by amine bonds, which represent the skeleton structure of pyrimidifen, a mitochondrial complex I-inhibiting insecticide. Replacing the pyrimidine moiety linked by the amine bond remarkably enhanced growth-inhibitory activity of the analogs against several human cancer cell lines. Moreover, these analogs selectively and potently inhibited the growth of these human cancer cell lines regardless of the pyrimidine substituents. Furthermore, COMPARE analyses suggested that these analogs inhibited cancer growth by inhibiting mitochondrial complex I. Our study provides insights into the design of acetogenin analogs as novel antitumor agents.

Gramicidin A accumulates in mitochondria, reduces ATP levels, induces mitophagy, and inhibits cancer cell growth.

Gramicidin A (1) is a linear 15-mer peptidic natural product. Because of its sequence of alternating d- and l-chirality, 1 folds into a ß6.3-helix in a lipid bilayer and forms a head-to-head dimer to function as a transmembrane channel for monovalent cations (H+, Na+, and K+). The potent anticancer activity of 1 was believed to be mainly attributed to the free ion diffusion across the plasma membrane. In this study, we investigated the cytostatic action of 1 in nanomolar concentrations using the human breast cancer cell line MCF-7, and revealed the unprecedented spatiotemporal behavior of 1 for the first time. Compound 1 not only disrupted the ion concentration gradients of the plasma membrane, but also localized in the mitochondria and depolarized the inner mitochondrial membrane. The diminished H+ gradient in the mitochondria inhibited ATP synthesis. The resultant mitochondrial malfunction led to mitophagy, while the cellular energy depletion induced G1 phase accumulation. The multiple events occurred in a time-dependent fashion and ultimately caused potent inhibition of cell growth. The present study provides valuable information for the design and development of new cytostatic agents exploiting channel-forming natural products.

Spautin-1 inhibits mitochondrial complex I and leads to suppression of the unfolded protein response and cell survival during glucose starvation.

The unfolded protein response (UPR) is an adaptive stress response pathway that is essential for cancer cell survival under endoplasmic reticulum stress such as during glucose starvation. In this study, we identified spautin-1, an autophagy inhibitor that suppresses ubiquitin-specific peptidase 10 (USP10) and USP13, as a novel UPR inhibitor under glucose starvation conditions. Spautin-1 prevented the induction of UPR-associated proteins, including glucose-regulated protein 78, activating transcription factor 4, and a splicing variant of x-box-binding protein-1, and showed preferential cytotoxicity in glucose-starved cancer cells. However, USP10 and USP13 silencing and treatment with other autophagy inhibitors failed to result in UPR inhibition and preferential cytotoxicity during glucose starvation. Using transcriptome and chemosensitivity-based COMPARE analyses, we identified a similarity between spautin-1 and mitochondrial complex I inhibitors and found that spautin-1 suppressed the activity of complex I extracted from isolated mitochondria. Our results indicated that spautin-1 may represent an attractive mitochondria-targeted seed compound that inhibits the UPR and cancer cell survival during glucose starvation.

Structure-antitumor activity relationship of hybrid acetogenins focusing on connecting groups between heterocycles and the linker moiety.

We studied hybrid molecules of annonaceous acetogenins and mitochondrial complex I-inhibiting insecticides to develop a novel anticancer agent. A structure-antitumor activity relationship study focusing on the connecting groups between the heterocycles and the linker moiety bearing the tetrahydrofuran moiety was conducted. Eleven hybrid acetogenins with 1-methylpyrazole instead of γ-lactone were synthesized and their growth inhibitory activities against 39 human cancer cell lines were evaluated. The nitrogen atom at the 2'-position of the linker moiety was essential for inhibiting cancer growth. The 1-methylpyrazole-5-sulfonamide analog showed potent growth inhibition of NCI-H23, a human lung cancer cell line, in a xenograft mouse assay without critical toxicity. Hence, the results of this study may pave the way for the development of novel anticancer agents, with both selective and broad anticancer activities.

Structural Determination, Total Synthesis, and Biological Activity of Iezoside, a Highly Potent Ca2+-ATPase Inhibitor from the Marine Cyanobacterium Leptochromothrix valpauliae.

Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is a membrane protein on the endoplasmic reticulum (ER) that transports Ca2+ from the cytosol into the ER. As its function is associated with various biological phenomena, SERCA has been recognized as a promising druggable target. Here, we report the second-strongest SERCA-inhibitory compound known to date, which we isolated from the marine cyanobacterium Leptochromothrix valpauliae and named iezoside (1). The structure of iezoside (1) is fundamentally different from that of any other SERCA inhibitor, and its potency is the strongest among marine natural products (Ki 7.1 nM). In this article, we report our comprehensive analysis of iezoside (1), which covers its isolation, structural characterization supported by density functional theory (DFT) calculations and statistical analysis, total synthesis, and clarification of the mode of action of its potent antiproliferative activity (IC50 6.7 ± 0.4 nM against HeLa cells).

Development of Low-Molecular-Weight Compounds Targeting the Cancer-Associated KLF5 Transcription Factor.

Krüppel-like factor 5 (KLF5) is a potential target for anticancer drugs. However, as an intrinsically disordered protein (IDP) whose tertiary structure cannot be solved, innovative strategies are needed. We focused on its hydrophobic α-helix structure, defined as an induced helical motif (IHM), which is a possible interface for protein-protein interaction. Using mathematical analyses predicting the α-helix's structure and hydrophobicity, a 4-amino-acid site (V-A-I-F) was identified as an IHM. Low-molecular-weight compounds that mimic the main chain conformation of the α-helix with the four side chains of V-A-I-F were synthesized using bicyclic pyrazinooxadiazine-4,7-dione. These compounds selectively suppressed the proliferation and survival of cancer cells but not noncancer cells and decreased the protein but not mRNA levels of KLF5 in addition to reducing proteins of Wnt signaling. The compounds further suppressed transplanted colorectal cancer cells in vivo without side effects. Our approach appears promising for developing drugs against key IDPs.

Suppression of tumor metastasis by a RECK-activating small molecule.

RECK encodes a membrane-anchored protease-regulator which is often downregulated in a wide variety of cancers, and reduced RECK expression often correlates with poorer prognoses. In mouse models, forced expression of RECK in tumor xenografts results in suppression of tumor angiogenesis, invasion, and metastasis. RECK mutations, however, are rare in cancer genomes, suggesting that agents that re-activate dormant RECK may be of clinical value. We found a potent RECK-inducer, DSK638, that inhibits spontaneous lung metastasis in our mouse xenograft model. Induction of RECK expression involves SP1 sites in its promoter and may be mediated by KLF2. DSK638 also upregulates MXI1, an endogenous MYC-antagonist, and inhibition of metastasis by DSK638 is dependent on both RECK and MXI1. This study demonstrates the utility of our approach (using a simple reporter assay followed by multiple phenotypic assays) and DSK638 itself (as a reference compound) in finding potential metastasis-suppressing drugs.

Isolation of new derivatives of the 20-membered macrodiolide bispolide from Kitasatospora sp. MG372-hF19.

New three macrocyclic diolides, named bispolides C-E (1-3), were isolated from a fermentation broth of the actinomycete strain MG372-hF19, which produces an indole glycoside and leptomycins as we reported previously. The absolute structures of compounds 1-3 were elucidated by NMR and X-ray crystallography. Compounds 1-3 diverge from the known nine bispolides in their different alkylation patterns on the 20-membered macrocyclic diolide skeleton and the side chain in their planar structures. Furthermore, compounds 1-3 exhibited antibacterial activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci and cytotoxic activity against human cancer cell lines. Among them, compound 3 has the most potent biological activities against bacteria and tumor cells. Additionally, using a membrane-potential-sensitive fluorescence probe, we found that compounds 1-3 and elaiophylin have a similar effect on membrane potential in A549 human lung cancer cells.

Mitochondrial complex I inhibitors suppress tumor growth through concomitant acidification of the intra- and extracellular environment.

The disruption of the tumor microenvironment (TME) is a promising anti-cancer strategy, but its effective targeting for solid tumors remains unknown. Here, we investigated the anti-cancer activity of the mitochondrial complex I inhibitor intervenolin (ITV), which modulates the TME independent of energy depletion. By modulating lactate metabolism, ITV induced the concomitant acidification of the intra- and extracellular environment, which synergistically suppressed S6K1 activity in cancer cells through protein phosphatase-2A-mediated dephosphorylation via G-protein-coupled receptor(s). Other complex I inhibitors including metformin and rotenone were also found to exert the same effect through an energy depletion-independent manner as ITV. In mouse and patient-derived xenograft models, ITV was found to suppress tumor growth and its mode of action was further confirmed. The TME is usually acidic owing to glycolytic cancer cell metabolism, and this condition is more susceptible to complex I inhibitors. Thus, we have demonstrated a potential treatment strategy for solid tumors.

Identification of Dihydroorotate Dehydrogenase Inhibitors─Indoluidins─That Inhibit Cancer Cell Growth.

Dihydroorotate dehydrogenase (DHODH) catalyzes the rate-limiting step in de novo pyrimidine biosynthesis and is a promising cancer treatment target. This study reports the identification of indoluidin D and its derivatives as inhibitors of DHODH. Cell-based phenotypic screening revealed that indoluidin D promoted myeloid differentiation and inhibited the proliferation of acute promyelocytic leukemia HL-60 cells. Indoluidin D also suppressed cell growth in various other types of cancer cells. Cancer cell sensitivity profiling with JFCR39 and proteomic profiling with ChemProteoBase revealed that indoluidin D is a DHODH inhibitor. Indoluidin D inhibited human DHODH activity in vitro; the DHODH reaction product orotic acid rescued indoluidin D-induced cell differentiation. We synthesized several indoluidin D diastereomer derivatives and demonstrated that stereochemistry was vital to their molecular activity. The indoluidin D derivative indoluidin E showed similar activity to its parent compound and suppressed tumor growth in a murine lung cancer xenograft model. Hence, indoluidin D and its derivatives selectively inhibit DHODH and suppress cancer cell growth.

Structure-Activity Relationships of Thiophene Carboxamide Annonaceous Acetogenin Analogs: Shortening the Alkyl Chain in the Tail Part Significantly Affects Their Growth Inhibitory Activity against Human Cancer Cell Lines.

In a previous study, we found that the thiophene carboxamide solamin analog, which is a mono-tetrahydrofuran annonaceous acetogenin, showed potent antitumor activity through the inhibition of mitochondrial complex I. In this study, we synthesized analogs with short alkyl chains instead of the n-dodecyl group in the tail part. We evaluated their growth inhibitory activities against human cancer cell lines. We found that the alkyl chain in the tail part plays an essential role in their activity.

Cancer immunotherapy with PI3K and PD-1 dual-blockade via optimal modulation of T cell activation signal.

BACKGROUND: Immune checkpoint blockade (ICB) induces durable clinical responses in patients with various types of cancer. However, its limited clinical efficacy requires the development of better approaches. In addition to immune checkpoint molecules, tumor-infiltrating immunosuppressive cells including regulatory T cells (Tregs) play crucial roles in the immune suppressive tumor microenvironment. While phosphatidylinositol 3-kinase (PI3K) inhibition as a Treg-targeted treatment has been implicated in animal models, its effects on human Tregs and on the potential impairment of effector T cells are required to be clarified for successful cancer immunotherapy. METHODS: The impact of a selective-PI3K inhibitor ZSTK474 with or without anti-programmed cell death 1 (PD-1) monoclonal antibody on Tregs and CD8+ T cells were examined with in vivo animal models and in vitro experiments with antigen specific and non-specific fashions using peripheral blood from healthy individuals and cancer patients. Phenotypes and functions of Tregs and effector T cells were examined with comprehensive gene and protein expression assays. RESULTS: Improved antitumor effects by the PI3K inhibitor in combination with ICB, particularly PD-1 blockade, were observed in mice and humans. Although administration of the PI3K inhibitor at higher doses impaired activation of CD8+ T cells as well as Tregs, the optimization (doses and timing) of this combination treatment selectively decreased intratumoral Tregs, resulting in increased tumor antigen-specific CD8+ T cells in the treated mice. Moreover, on the administration of the PI3K inhibitor with the optimal dose for selectively deleting Tregs, PI3K signaling was inhibited not only in Tregs but also in activated CD8+ T cells, leading to the enhanced generation of tumor antigen-specific memory CD8+ T cells which contributed to durable antitumor immunity. These opposing outcomes between Tregs and CD8+ T cells were attributed to the high degree of dependence on T cell signaling in the former but not in the latter. CONCLUSIONS: PI3K inhibitor in the combination with ICB with the optimized protocol fine-tuned T cell activation signaling for antitumor immunity via decreasing Tregs and optimizing memory CD8+ T cell responses, illustrating a promising combination therapy.

Lamellarin 14, a derivative of marine alkaloids, inhibits the T790M/C797S mutant epidermal growth factor receptor.

The emergence of acquired resistance is a major concern associated with molecularly targeted kinase inhibitors. The C797S mutation in the epidermal growth factor receptor (EGFR) confers resistance to osimertinib, a third-generation EGFR-tyrosine kinase inhibitor (EGFR-TKI). We report that the derivatization of the marine alkaloid topoisomerase inhibitor lamellarin N provides a structurally new class of EGFR-TKIs. One of these, lamellarin 14, is effective against the C797S mutant EGFR. Bioinformatic analyses revealed that the derivatization transformed the topoisomerase inhibitor-like biological activity of lamellarin N into kinase inhibitor-like activity. Ba/F3 and PC-9 cells expressing the EGFR in-frame deletion within exon 19 (del ex19)/T790M/C797S triple-mutant were sensitive to lamellarin 14 in a dose range similar to the effective dose for cells expressing EGFR del ex19 or del ex19/T790M. Lamellarin 14 decreased the autophosphorylation of EGFR and the downstream signaling in the triple-mutant EGFR PC-9 cells. Furthermore, intraperitoneal administration of 10 mg/kg lamellarin 14 for 17 days suppressed tumor growth of the triple-mutant EGFR PC-9 cells in a mouse xenograft model using BALB/c nu/nu mice. Thus, lamellarin 14 serves as a novel structural backbone for an EGFR-TKI that prevents the development of cross-resistance against known drugs in this class.

Effects of side chain length of 10-methyl-aplog-1, a simplified analog of debromoaplysiatoxin, on PKC binding, anti-proliferative, and pro-inflammatory activities.

10-Methyl-aplog-1 (1), a simplified analog of debromoaplysiatoxin, exhibits a high binding affinity for protein kinase C (PKC) isozymes and potent antiproliferative activity against several cancer cells with few adverse effects. A recent study has suggested that its phenol group in the side chain is involved in hydrogen bonding and CH/π interactions with the binding cleft-forming loops in the PKCδ-C1B domain. To clarify the effects of the side chain length on these interactions, four analogs of 1 with various lengths of side chains (2-5) were prepared. The maximal PKC binding affinity and antiproliferative activity were observed in 1. Remarkably, the introduction of a bromine atom into the phenol group of 2 increased not only these activities but also proinflammatory activity. These results indicated that 1 has the optimal side chain length as an anticancer seed. This conclusion was supported by docking simulations of 1-5 to the PKCδ-C1B domain.