Antineoplastics for treating Alzheimer's disease and dementia: Evidence from preclinical and observational studies

As the world population ages, there will be an increasing need for effective therapies for aging-associated neurodegenerative disorders, which remain untreatable. Dementia due to Alzheimer's disease (AD) is one of the leading neurological diseases in the aging population. Current therapeutic approaches to treat this disorder are solely symptomatic, making the need for new molecular entities acting on the causes of the disease extremely urgent. One of the potential solutions is to use compounds that are already in the market. The structures have known pharmacokinetics, pharmacodynamics, toxicity profiles, and patient data available in several countries. Several drugs have been used successfully to treat diseases different from their original purposes, such as autoimmunity and peripheral inflammation. Herein, we divulge the repurposing of drugs in the area of neurodegenerative diseases, focusing on the therapeutic potential of antineoplastics to treat dementia due to AD and dementia. We briefly touch upon the shared pathological mechanism between AD and cancer and drug repurposing strategies, with a focus on artificial intelligence. Next, we bring out the current status of research on the development of drugs, provide supporting evidence from retrospective, clinical, and preclinical studies on antineoplastic use, and bring in new areas, such as repurposing drugs for the prion-like spreading of pathologies in treating AD.

Novel 5-Substituted Oxindole Derivatives as Bruton's Tyrosine Kinase Inhibitors: Design, Synthesis, Docking, Molecular Dynamics Simulation, and Biological Evaluation

Bruton's tyrosine kinase (BTK) is a non-RTK cytoplasmic kinase predominantly expressed by hemopoietic lineages, particularly B-cells. A new oxindole-based focused library was designed to identify potent compounds targeting the BTK protein as anticancer agents. This study used rational approaches like structure-based pharmacophore modeling, docking, and ADME properties to select compounds. Molecular dynamics simulations carried out at 20 ns supported the stability of compound 9g within the binding pocket. All the compounds were synthesized and subjected to biological screening on two BTK-expressing cancer cell lines, RAMOS and K562; six non-BTK cancer cell lines, A549, HCT116 (parental and p53-/-), U2OS, JURKAT, and CCRF-CEM; and two non-malignant fibroblast lines, BJ and MRC-5. This study resulted in the identification of four new compounds, 9b, 9f, 9g, and 9h, possessing free binding energies of -10.8, -11.1, -11.3, and -10.8 kcal/mol, respectively, and displaying selective cytotoxicity against BTK-high RAMOS cells. Further analysis demonstrated the antiproliferative activity of 9h in RAMOS cells through selective inhibition of pBTK (Tyr223) without affecting Lyn and Syk, upstream proteins in the BCR signaling pathway. In conclusion, we identified a promising oxindole derivative (9h) that shows specificity in modulating BTK signaling pathways.

Synthesis and Biological Evaluation of Oxindole Sulfonamide Derivatives as Bruton's Tyrosine Kinase Inhibitors

Bruton's tyrosine kinase (BTK) is a promising molecular target for several human B-cell-related autoimmune disorders, inflammation, and haematological malignancies. The pathogenic alterations in various cancer tissues depend on mutant BTK for cell proliferation and survival, and BTK is also overexpressed in a range of hematopoietic cells. Due to this, BTK is emerging as a potential drug target to treat various human diseases, and several reversible and irreversible inhibitors have been developed and are being developed. As a result, BTK inhibition, clinically validated as an anticancer treatment, is finding great interest in B-cell malignancies and solid tumours. This study focuses on the design and synthesis of new oxindole sulfonamide derivatives as promising inhibitors of BTK with negligible off-target effects. The most cytotoxic compounds with greater basicity were PID-4 (2.29±0.52 μM), PID-6 (9.37±2.47 μM), and PID-19 (2.64±0.88 μM). These compounds caused a selective inhibition of Burkitt's lymphoma RAMOS cells without significant cytotoxicity in non-BTK cancerous and non-cancerous cell lines. Further, PID-4 showed promising activity in inhibiting BTK and downstream signalling cascades. As a potent inhibitor of Burkitt's lymphoma cells, PID-4 is a promising lead for developing novel chemotherapeutics.

Inflammation, Autoimmunity and Neurodegenerative Diseases, Therapeutics and Beyond

Neurodegenerative disease (ND) incidence has recently increased due to improved life expectancy. Alzheimer's (AD) or Parkinson's disease (PD) are the most prevalent NDs. Both diseases are poly genetic, multifactorial and heterogenous. Preventive medicine, a healthy diet, exercise, and controlling comorbidities may delay the onset. After the diseases are diagnosed, therapy is needed to slow progression. Recent studies show that local, peripheral and age-related inflammation accelerates NDs' onset and progression. Patients with autoimmune disorders like inflammatory bowel disease (IBD) could be at higher risk of developing AD or PD. However, no increase in ND incidence has been reported if the patients are adequately diagnosed and treated. Autoantibodies against abnormal tau, β amyloid and α- synuclein have been encountered in AD and PD and may be protective. This discovery led to the proposal of immune-based therapies for AD and PD involving monoclonal antibodies, immunization/ vaccines, pro-inflammatory cytokine inhibition and anti-inflammatory cytokine addition. All the different approaches have been analysed here. Future perspectives on new therapeutic strategies for both disorders are concisely examined.

Time- and dose-dependent seeding tendency of exogenous tau R2 and R3 aggregates in cells

Tauopathies are a group of neurodegenerative diseases categorised into three types, 3R, 4R, or 3R+4R (mixed) tauopathies, based on the tau isoforms that make up the aberrant filaments. It is supposed that all six tau isoforms share functional characteristics. However, differences in the neuropathological features associated with different tauopathies offer the possibility that disease progression and tau accumulation may vary depending on the isoform composition. The presence or absence of repeat 2 (R2) in the microtubule-binding domain defines the type of isoform, which might influence tau pathology associated with a particular tau isoform. Therefore, our study aimed to identify the differences in the seeding propensities of R2 and repeat 3 (R3) aggregates using HEK293T biosensor cells. We show that the seeding induced by R2 was generally higher than by R3 aggregates, and lower concentrations of R2 aggregates are sufficient to induce seeding. Next, we found that both R2 and R3 aggregates dose-dependently increased triton-insoluble Ser262 phosphorylation of native tau, which is only visible in cells seeded with higher concentrations (12.5 nM or 100 nM) of R2 and R3 aggregates, despite the seeding by the lower concentrations of R2 aggregates after 72 h. However, the accumulation of triton-insoluble pSer262 tau was visible earlier in cells induced with R2 than in R3 aggregates. Our findings suggest that the R2 region may contribute to the early and enhanced induction of tau aggregation and define the difference in disease progression and neuropathology of 4R tauopathies.

Tau R2 and R3 are essential regions for tau aggregation, seeding and propagation

Tauopathies are characterised by intracellular deposits of fibrillar tau tangles. However, the interneuronal spread of pathological tau species precedes the development of major tau burdens. Two amyloid motifs, VQIINK in repeat 2 and VQIVYK in repeat 3, of tau repeat domain, assemble into β-sheet-rich fibrils on their own but alone do not form seed-competent fibrils. In contrast, the entire R3 region self-aggregates and forms seed-competent fibrils. Our study aimed to identify the minimal regions in the tau repeat domain that define seeding and its impact on intracellular tau phosphorylation and aggregation. Using peptides of individual repeats, we show that R2, like R3, forms seed-competent fibrils when assembled in the presence of heparin. However, R3, but not R2, forms seed-competent fibrils when assembled without heparin, even though both R2 and R3 have identical N-terminal hexapeptide and cysteine residue sequences. Moreover, cysteine to alanine substitution in R3 abrogates its self-aggregation and seeding potency. Tau RD P301S biosensor cells and Tau P301L (0N4R)-expressing HEK293 cells seeded with R2 and R3 fibrils show the induction of pathological phosphorylation of tau at Ser262/Ser396/Ser404 positions and oligomerisation of native tau. Protein fractions of biosensor cells seeded with R2 and R3 fibrils reseed endogenous tau aggregation when introduced into a fresh set of biosensor cells. Our findings suggest that R3 may be the minimal region for pathological seed generation under physiological conditions, whereas R2 might need polyanionic cofactors to generate pathogenic seeds. Lastly, R2 and R3 fibrils induce template-induced misfolding and pathological hyperphosphorylation of intracellular tau, making intracellular tau seed-competent.

Antitumour drugs targeting tau R3 VQIVYK and Cys322 prevent seeding of endogenous tau aggregates by exogenous seeds

Emerging experimental evidence suggests tau pathology spreads between neuroanatomically connected brain regions in a prion-like manner in Alzheimer's disease (AD). Tau seeding, the ability of prion-like tau to recruit and misfold naïve tau to generate new seeds, is detected early in human AD brains before the development of major tau pathology. Many antitumour drugs have been reported to confer protection against neurodegeneration, supporting the repurposing of approved and experimental or investigational oncology drugs for AD therapy. In this study, we evaluated whether antitumour drugs that abrogate the generation of seed-competent aggregates of tau Repeat 3 (R3) domain peptides can prevent tau seeding and toxicity in Tau-RD P301S FRET Biosensor cells and Caenorhabditis elegans. We demonstrate that drugs that interact with the N-terminal VQIVYK or the C-terminal region housing the Cys322 prevent R3 dimerisation, abolishing the generation of prion-like R3 seeds. Preformed R3 seeds (fibrils) capped with, or R3 seeds formed in the presence of VQIVYK- or Cys322-targeting drugs have a reduced potency to cause aggregation of naïve tau in biosensor cells and protect worms from aggregate toxicity. These findings indicate that VQIVYK- or Cys322-targeting drugs may act as prophylactic agents against tau seeding.

Tau secretion and propagation: Perspectives for potential preventive interventions in Alzheimer's disease and other tauopathies

Alzheimer's disease (AD) is characterised by the accumulation of intracytoplasmic aggregates of tau protein, which are suggested to spread in a prion-like manner between interconnected brain regions. This spreading is mediated by the secretion and uptake of tau from the extracellular space or direct cell-to-cell transmission through cellular protrusions. The prion-like tau then converts the endogenous, normal tau into pathological forms, resulting in neurodegeneration. The endoplasmic reticulum/Golgi-independent tau secretion through unconventional secretory pathways involves delivering misfolded and aggregated tau to the plasma membrane and its release into the extracellular space by non-vesicular and vesicular mechanisms. Although cytoplasmic tau was thought to be released only from degenerating cells, studies now show that cells constitutively secrete tau at low levels under physiological conditions. The mechanisms of secretion of tau under physiological and pathological conditions remain unclear. Therefore, a better understanding of these pathways is essential for developing therapeutic approaches that can target prion-like tau forms to prevent neurodegeneration progression in AD. This review focuses on unconventional secretion pathways involved in the spread of tau pathology in AD and presents these pathways as prospective areas for future AD drug discovery and development.

Abstract 3470: The antagonistic functional duality of p21WAF1/CIP1 in cells derived from multicellular tumor spheroids

The cyclin-dependent kinase inhibitor p21WAF1/CIP1 (p21) is a key mediator of p53-dependent cell cycle arrest after DNA damage, in addition to p53-independent mechanisms. Being one of the major transcriptional targets of p53 and due to its anti-cell proliferative activity, p21 was considered initially as a potent tumor suppressor. However, emerging studies now show the anti-apoptotic and pro-cell proliferative effects of p21, highlighting the oncogenic role of p21 in cancer. In particular, p21 results in genomic instability and the development of aggressive and chemo-resistant traits in a subset of highly proliferating tumor cells through p53-independent pathways. The cellular localization of p21 has been proposed to be critical either in promoting cell survival or in inhibiting cell growth. Herein, using a combination of gene knockout, cytotoxicity assay, immunofluorescence, immunoprecipitation, and mass spectrometry techniques, we study the consequence of nuclear and cytoplasmic localization of p21 on cell survival and drug response in cells derived from multicellular spheroids of multiple human cancer cell lines. Our study shows that cells derived from multicellular spheroids show an increased induction of p21 despite the reversal from three-dimensional to two-dimensional cultures. The p21-overexpressing, highly proliferative cells are significantly resistant to a number of standard anti-cancer agents. Further analysis shows that the majority of p21 in this subset of spheroid-derived cells is localized in the cytoplasm and forms a potential 'anti-apoptosome'-like complex with mitochondrial apoptosis-associated proteins. These findings add to the shifting paradigm on the oncogenic role p21 due to cellular mislocalization in tumor cells.

Citation Format: Viswanath Das, Narendran Annadurai, Dušan Holub, Marián Hajdúch. The antagonistic functional duality of p21WAF1/CIP1 in cells derived from multicellular tumor spheroids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3470.

Abstract 4474: An intricate role of p53 and p21 in cellular alterations and drug penetration in spheroids of colorectal cancer cells

The tumor protein p53 and cyclin-dependent kinase inhibitor p21Waf1/Cip1 (p21) are two proteins with an intriguing and a paradoxical role in cancer. Through p53-dependent signals, p21 negatively controls cell cycle progression to protect cells against deleterious effects of DNA damage. Although p53 is a tumor suppressor protein, recent evidence shows that some patients with wild-type (wt) p53 develop aggressive and drug-resistant cancers. Similarly, recent studies also suggest the oncogenic role of p21. In a p53 deficient background, p21 results in the development of a subset of highly proliferative and resistant population of cancer cells.

In this study, we examined the role of p53 and p21 in inducing cellular alterations using a panel of colorectal carcinoma cell lines with different p53 and p21 background and spheroid and spheroid-derived cell cultures. First, our data show that despite the presence of proliferating cells, spheroid-derived cultures of HCT116/p53wt cells continue to display an elevated p21 level even after 6 days of culture as a monolayer. These p21-overexpressing proliferating cells show increased resistance to doxorubicin and paclitaxel in comparison to their parental monolayer counterpart. In contrast to HCT116/p53wt cells, DLD-1/p53mut cells did not show elevated p21 levels following reversal from spheroid to monolayer. The increased p21 level in spheroids and spheroid-derived cultures of HCT116/p53wt cells led us to examine the role of p53 and p21 in drug penetration. Spheroids of HCT116/p53wt cells were less permeable to doxorubicin and showed increased expression of intracellular junctional (IJ) proteins (adherens and tight junctions). Knocking-out p21 in HCT116/p53wt cells decreased the level of IJ proteins, resulting in an increased doxorubicin penetration. Re-expression of p21 in p21-knocked-out HCT116/p53wt cells restored IJ protein levels, reducing doxorubicin penetration and the subsequent effect of doxorubicin on spheroids. Interestingly, however, knocking-out p21 in DLD-1/p53mut cells neither altered intracellular junctions nor affected doxorubicin penetration. These data indicate that the effect of p21 on IJ proteins and drug penetration is pertinent only in cells with wt p53. Overall, the data from our study suggest an intricate interplay between wt p53 and p21 in inducing cellular alterations that affect the sensitivity of cells to anti-cancer drugs in spheroids.

Citation Format: Viswanath Das, Narendran Annadurai, Marián Hajdúch. An intricate role of p53 and p21 in cellular alterations and drug penetration in spheroids of colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4474.

Peloruside A-Induced Cell Death in Hypoxia Is p53 Dependent in HCT116 Colorectal Cancer Cells

HCT116 colorectal cancer cell sensitivity to peloruside A (PLA) in normoxia is not altered by hypoxia preconditioning of the cells. We examined whether the PLA effects were altered in hypoxia and whether the activity was dependent on p53. The cytotoxicity of PLA in wild-type HCT116 cells was largely unaffected by hypoxia; however, cells in which p53 was knocked out showed resistance. Knockout of the p21 gene had little effect on the activity of PLA in hypoxia. It was concluded that the response of cells to the microtubule-stabilizing agent PLA under hypoxic conditions is a p53-dependent process.