B.T. Prabhakar

Synthesis and tumor inhibitory activity of novel coumarin analogs targeting angiogenesis and apoptosis.

A sequence of coumarin analogs 5a-j was obtained by multi step synthesis from hydroxy benzophenones (1a-j). The in vitro antiproliferative effect of the title compounds was tested against Ehrlich ascites carcinoma (EAC) and Daltons lymphoma ascites (DLA) cell lines. Among the series, compound 5c with bromo group in the benzophenone moiety was endowed with excellent antiproliferative potency with significant IC50 value. Further, in vivo antitumor effect of compound 5c against murine EAC and solid DL tumor model system was evident by the extended survivality. The tumor inhibitory mechanism of compound 5c was due to the antiangiogenesis and promotion of apoptosis. These results suggest possible applications of compound 5c which could be developed as a potent anticancer drug in the near future.

Synthesis, angiopreventive activity, and in vivo tumor inhibition of novel benzophenone-benzimidazole analogs.

AIM The development of anticancer drugs with specific targets is of prime importance in modern biology. This study investigates the angiopreventive and in vivo tumor inhibition activities of novel synthetic benzophenone-benzimidazole analogs. MAIN METHODS The multistep synthesis of novel benzophenone-benzimidazole analogs (8a-n) allowing substitution with methoxy, methyl and halogen groups at different positions on the identical chemical backbone and the variations in the number of substituents were synthesized and characterized. The newly synthesized compounds were further evaluated for cytotoxic and antiproliferative effects against Ehrlich ascites carcinoma (EAC) cells. The potent lead compounds were further assessed for antiangiogenic effects in a CAM model and a tumor-induced vasculature in vivo model. The effect of angioprevention on tumor growth was verified in a mouse model. KEY FINDINGS The cytotoxicity studies revealed that compounds 8f and 8n are strongly cytotoxic. Analyzing the structure-activity relationship, we found that an increase in the number of methyl groups in addition to methoxy substitution at the para position of the benzoyl ring in compound 8n resulted in higher potency compared to 8f. Furthermore, neovessel formation in in vivo systems, such as the chorioallantoic membrane (CAM) and tumor-induced mice peritoneum models, was significantly suppressed and reflected the tumor inhibition observed in mice. SIGNIFICANCE These results suggest the potential clinical application of compound 8n as an antiangiogenic drug for cancer therapy.

Synthesis of oxadiazole-morpholine derivatives and manifestation of the repressed CD31 Microvessel Density (MVD) as tumoral angiogenic parameters in Dalton's Lymphoma.

A series of oxadiazole derivatives possessing morpholine 6a-l were synthesized by nucleophilic substitution reaction of key intermediates [1,3,4]-oxadiazole-2-thiol derivatives 5a-l with 4-(2-chloroethyl) morpholine. Compounds 6a-l were evaluated for their in vitro and in vivo antitumor potential in Daltons Lymphoma Ascites (DLA) tumor cells. Among 6a-l series, compound 6a with concentration ∼8.5μM have shown extensive cytotoxicity in vitro and 85% reduction in tumor volume in vivo, attributing an excellent anti-proliferative capability towards the cancer cells. Compound 6a has extensively inhibited the Microvessel Density (MVD) or tumoral neovasculature which was evident from the CD31 immuno staining and peritoneal H&E staining. The major reason for the antiproliferative activity of compound 6a was due to the repression of tumor vasculature.

BP-1T, an antiangiogenic benzophenone-thiazole pharmacophore, counteracts HIF-1 signalling through p53/MDM2-mediated HIF-1α proteasomal degradation

Hypoxia is a feature of all solid tumours, contributing to tumour progression. Activation of HIF-1α plays a critical role in promoting tumour angiogenesis and metastasis. Since its expression is positively correlated with poor prognosis for cancer patients, HIF-1α is one of the most convincing anticancer targets. BP-1T is a novel antiproliferative agent with promising antiangiogenic effects. In the present study, the molecular mechanism underlying cytotoxic/antiangiogenic effects of BP-1T on tumour/non-tumour angiogenesis was evaluated. Evidences show that BP-1T exhibits potent cytotoxicity with prolonged activity and effectively regressed neovessel formation both in reliable non-tumour and tumour angiogenic models. The expression of CoCl2-induced HIF-1α was inhibited by BP-1T in various p53 (WT)-expressing cancer cells, including A549, MCF-7 and DLA, but not in mutant p53-expressing SCC-9 cells. Mechanistically, BP-1T mediates the HIF-1α proteasomal degradation by activating p53/MDM2 pathway and thereby downregulated HIF-1α-dependent angiogenic genes such as VEGF-A, Flt-1, MMP-2 and MMP-9 under hypoxic condition of in vitro and in vivo solid tumour, eventually leading to abolition of migration and invasion. Based on these observations, we conclude that BP-1T acts on HIF-1α degradation through p53/MDM2 proteasome pathway.

DAO-9 (2,5-di(4-aryloylaryloxymethyl)-1,3,4-oxadiazole) exhibits p53 induced apoptogenesis through caspase-3 mediated endonuclease activity in murine carcinoma

One of the main strategies to inhibit the tumor growth is to promote the biochemical events leading to DNA degradation, which would eventually culminate in apoptosis. We have earlier reported that the 2,5-di(4-aryloylaryloxymethyl)-1,3,4-oxadiazole(DAO-9) possessed anti-cancer activity. To address the exact molecular mechanism underlying anti-cancer property, present study focused on evaluating the anti-tumor effect of the DAO-9 on murine ascites carcinoma cells using various in vivo and in vitro assays. The in vivo assays implicated a strong regression in tumor growth of ascites carcinoma after treatment which is due to apoptogenic efficacy as assessed through structural morphology of EAC cells by Giemsa, Acridine orange, Annexin V staining and FACS analysis. Nucleosomal DNA fragmentation induced by DAO-9 is due to activation of caspase-3 mediated DNAse as verified by endonuclease assays and immunoblot analysis. The caspase-3 activation mechanism is by induction of intrinsic cascade signaling molecules, such as p53, Bax, Bad and cytochrome c (cyt c) expression as verified by western blot. The results concluded that the tumor inhibiting activity of DAO-9 is due to activation of the apoptotic signaling cascade, which could be translated into targeted anti-cancer drug in the near future.

Synthesis and evaluation of novel benzophenone-thiazole derivatives as potent VEGF-A inhibitors

A series of 2-(4-benzoyl-phenoxy)-N-(4-phenyl-thiazol-2-yl)-acetamides (10a-n) were synthesized by multistep reaction sequence and all the compounds were well characterized for structural elucidation. The in vitro cytotoxicity of compounds 10a-n was evaluated against EAC and DLA cell lines using trypan blue dye exclusion method. Further MTT assay and LDH release assay, followed by in vivo studies on murine model were also evaluated. The compound 10h with a methyl and fluoro groups at benzophenone moiety and methoxy group at phenyl ring was in a leading position to exhibit the promising antiproliferative effect through translational VEGF-A inhibition.

New role of lupeol in reticence of angiogenesis, the cellular parameter of neoplastic progression in tumorigenesis models through altered gene expression.

There is a major unmet medical need for effective and well tolerated treatment options for cancer. The search now seeks to identify active biomolecules with multiple targets. Lupeol, an important dietary triterpenoid known as anticarcinogen by inducing apoptosis. But it is still more to reveal the potency of lupeol in the inhibition of neovascularization in cancer context. The study aimed to explore the efficacy of the lupeol in targeting angiogenesis. In this study, the inhibition of neovessel formation was assessed by preliminary antiangiogenesis assays like chorio allontoic membrane (CAM) and rat corneal micro pocket models. Further, validated for the micro vessel density (MVD) in histological sections of peritoneum, solid tumor and xenograft tumor by immunostaining with anti CD31 antibody. Antitumor potency was verified in ascites carcinoma, solid lymphoma and human nueroblastoma xenograft in CAM. Altered angiogenic gene expression by RT-PCR, ELISA and gelatin zymography. Lupeol significantly inhibits the neovessel formation in CAM and in the rat cornea. The similar effect was ascertained in mice and human xenograft tumor models with the regressed growth. Eventually reflecting on the differential transcription of angiogenic genes like MMP-2 & 9, HIF-1α, VEGFa and Flt-1 was noteworthy. It is now evident from our studies that, a new avenue of dietary triterpenoid lupeol by targeting angiogenesis, potentially inferring the multimode action in cancer prevention.

A tumoural angiogenic gateway blocker, Benzophenone-1B represses the HIF-1α nuclear translocation and its target gene activation against neoplastic progression

Graphical abstract Figure. No Caption available. ABSTRACT Hypoxia is an important module in all solid tumours to promote angiogenesis, invasion and metastasis. Stabilization and subsequent nuclear localization of HIF‐1&agr; subunits result in the activation of tumour promoting target genes such as VEGF, MMPs, Flt‐1, Ang‐1 etc. which plays a pivotal role in adaptation of tumour cells to hypoxia. Increased HIF‐&agr; and its nuclear translocation have been correlated with pronounced angiogenesis, aggressive tumour growth and poor patient prognosis leading to current interest in HIF‐1&agr; as an anticancer drug target. Benzophenone‐1B ([4‐(1H‐benzimidazol‐2‐ylmethoxy)‐3,5‐dimethylphenyl]‐(4‐methoxyphenyl) methanone, or BP‐1B) is a new antineoplastic agent with potential angiopreventive effects. Current investigation reports the cellular biochemical modulation underlying BP‐1B cytotoxic/antiangiogenic effects. Experimental evidences postulate that BP‐1B exhibits the tumour specific cytotoxic actions against various cancer types with prolonged action. Moreover BP‐1B efficiently counteracts endothelial cell capillary formation in in‐vitro, in‐vivo non‐tumour and tumour angiogenic systems. Molecular signaling studies reveal that BP‐1B arrests nuclear translocation of HIF‐1&agr; devoid of p42/44 pathway under CoCl2 induced hypoxic conditions in various cancer cells thereby leading to abrogated HIF‐1&agr; dependent activation of VEGF‐A, Flt‐1, MMP‐2, MMP ‐9 and Ang‐1 angiogenic factors resulting in retarded cell migration and invasions. The in‐vitro results were reproducible in the reliable in‐vivo solid tumour model. Taken together, we conclude that BP‐1B impairs angiogenesis by blocking nuclear localization of HIF‐1&agr; which can be translated into a potent HIF‐1&agr; inhibitor.

The latex sap of the ‘Old World Plant’ Lagenaria siceraria with potent lectin activity mitigates neoplastic malignancy targeting neovasculature and cell death

Lifestyle and dietary modifications have contributed much to somatic genetic alteration which has concomitantly led to increase in malignant diseases. Henceforth, plant based and dietary interventions to mitigate and impede oncogenic transformation are in great demand. We investigated the latex sap (LSL) of the dietary Lagenaria siceraria vegetable, the first domesticated plant species with the potent lectin activity for its functional role against the tumor progression and its mechanism. LSL has markedly stimulated proliferation of lymphocytes and displayed strong cytotoxic activity against cancer both in-vitro and in-vivo. The tumor regression was paralleled with drastic reduction in tumoral neovasculature as evidenced from angiogenic parameters and abrogated related gene expressions. LSL has also triggered apoptotic signaling cascade in cancer cells through activation of caspase-3 mediated activation of endonuclease and inducing apoptotic cellular events. Collectively our study provides tangible evidences that latex sap from L. siceraria with immunopotentiating ability significantly regresses the tumor progression by targeting angiogenesis and inducing cell death.

Synthesis and antiproliferative activity of benzophenone tagged pyridine analogues towards activation of caspase activated DNase mediated nuclear fragmentation in Dalton’s lymphoma

A series of benzophenones possessing pyridine nucleus 8a-l were synthesized by multistep reaction sequence and evaluated for antiproliferative activity against DLA cells by in vitro and in vivo studies. The results suggested that, compounds 8b with fluoro group and 8e with chloro substituent at the benzoyl ring of benzophenone scaffold as well as pyridine ring with hydroxy group exhibited significant activity. Further investigation in mouse model suggests that compounds 8b and 8e have the potency to activate caspase activated DNase (endonuclease) which is responsible for DNA fragmentation, a primary hallmark of apoptosis and thereby inhibits the Daltons lymphoma ascites tumour growth.