Tankyrase inhibition sensitizes cells to CDK4 blockade

A potent and selective TNKS2 inhibitor for tumor-selective WNT suppression

Hyperactive WNT signaling is a potent cancer driver, but clinical translation of WNT inhibitors has been hampered by on-target toxicities. WNT signaling can be constrained through inhibition of the PARP family enzymes Tankyrase 1 (TNKS1) and Tankyrase 2 (TNKS2), however, existing TNKS inhibitors suppress WNT signaling in both tumor and healthy tissues. In this study, we show that the loss of chromosome 8p that occurs in approximately half of advanced epithelial malignancies, creates a collateral vulnerability that enables tumor-selective inhibition of Tankyrase activity. 8p loss depletes expression of TNKS1 and creates a tumor-specific dependency on the functionally redundant TNKS2 protein. Through structure-guided drug design, we identify a first-in-class TNKS2-selective inhibitor that can drive selective WNT inhibition in TNKS1-deficient oncogenic cell and organoid models. This work demonstrates a targetable vulnerability in multiple cancer types, providing a new approach to potent and selective WNT-targeted therapies.

Kinome-Focused CRISPR-Cas9 Screens in African Ancestry Patient-Derived Breast Cancer Organoids Identify Essential Kinases and Synergy of EGFR and FGFR1 Inhibition

Precision medicine approaches to cancer treatment aim to exploit genomic alterations that are specific to individual patients to tailor therapeutic strategies. Yet, some targetable genes and pathways are essential for tumor cell viability even in the absence of direct genomic alterations. In underrepresented populations, the mutational landscape and determinants of response to existing therapies are poorly characterized because of limited inclusion in clinical trials and studies. One way to reveal tumor essential genes is with genetic screens. Most screens are conducted on cell lines that bear little resemblance to patient tumors, after years of culture under nonphysiologic conditions. To address this problem, we aimed to develop a CRISPR screening pipeline in three-dimensionally grown patient-derived tumor organoid (PDTO) models. A breast cancer PDTO biobank that focused on underrepresented populations, including West African patients, was established and used to conduct a negative-selection kinome-focused CRISPR screen to identify kinases essential for organoid growth and potential targets for combination therapy with EGFR or MEK inhibitors. The screen identified several previously unidentified kinase targets, and the combination of FGFR1 and EGFR inhibitors synergized to block organoid proliferation. Together, these data demonstrate the feasibility of CRISPR-based genetic screens in patient-derived tumor models, including PDTOs from underrepresented patients with cancer, and identify targets for cancer therapy. Significance: Generation of a breast cancer patient-derived tumor organoid biobank focused on underrepresented populations enabled kinome-focused CRISPR screening that identified essential kinases and potential targets for combination therapy with EGFR or MEK inhibitors. See related commentary by Trembath and Spanheimer, p. 407.

Pharmacological modulation of RB1 activity mitigates resistance to neoadjuvant chemotherapy in locally advanced rectal cancer

Resistance to neoadjuvant chemotherapy leads to poor prognosis of locally advanced rectal cancer (LARC), representing an unmet clinical need that demands further exploration of therapeutic strategies to improve clinical outcomes. Here, we identified a noncanonical role of RB1 for modulating chromatin activity that contributes to oxaliplatin resistance in colorectal cancer (CRC). We demonstrate that oxaliplatin induces RB1 phosphorylation, which is associated with the resistance to neoadjuvant oxaliplatin-based chemotherapy in LARC. Inhibition of RB1 phosphorylation by CDK4/6 inhibitor results in vulnerability to oxaliplatin in both intrinsic and acquired chemoresistant CRC. Mechanistically, we show that RB1 modulates chromatin activity through the TEAD4/HDAC1 complex to epigenetically suppress the expression of DNA repair genes. Antagonizing RB1 phosphorylation through CDK4/6 inhibition enforces RB1/TEAD4/HDAC1 repressor activity, leading to DNA repair defects, thus sensitizing oxaliplatin treatment in LARC. Our study identifies a RB1 function in regulating chromatin activity through TEAD4/HDAC1. It also provides the combination of CDK4/6 inhibitor with oxaliplatin as a potential synthetic lethality strategy to mitigate oxaliplatin resistance in LARC, whereby phosphorylated RB1/TEAD4 can serve as potential biomarkers to guide the patient stratification.

Contribution of MicroRNAs in Chemoresistance to Cisplatin in the Top Five Deadliest Cancer: An Updated Review

Cisplatin (DDP) is a well-known anticancer drug used for the treatment of numerous human cancers in solid organs, including bladder, breast, cervical, head and neck squamous cell, ovarian, among others. Its most important mode of action is the DNA-platinum adducts formation, inducing DNA damage response, silencing or activating several genes to induce apoptosis; these mechanisms result in genetics and epigenetics modifications. The ability of DDP to induce tumor cell death is often challenged by the presence of anti-apoptotic regulators, leading to chemoresistance, wherein many patients who have or will develop DDP-resistance. Cancer cells resist the apoptotic effect of chemotherapy, being a problem that severely restricts the successful results of treatment for many human cancers. In the last 30 years, researchers have discovered there are several types of RNAs, and among the most important are non-coding RNAs (ncRNAs), a class of RNAs that are not involved in protein production, but they are implicated in gene expression regulation, and representing the 98% of the human genome non-translated. Some ncRNAs of great interest are long ncRNAs, circular RNAs, and microRNAs (miRs). Accumulating studies reveal that aberrant miRs expression can affect the development of chemotherapy drug resistance, by modulating the expression of relevant target proteins. Thus, identifying molecular mechanisms underlying chemoresistance development is fundamental for setting strategies to improve the prognosis of patients with different types of cancer. Therefore, this review aimed to identify and summarize miRs that modulate chemoresistance in DDP-resistant in the top five deadliest cancer, both in vitro and in vivo human models.

Small-Molecule Inhibitors of Tankyrases as Prospective Therapeutics for Cancer

Tankyrases are multifunctional poly(adenosine diphosphate-ribose) polymerases that regulate diverse biological processes including telomere maintenance and cellular signaling. These processes are often implicated in a number of human diseases, with cancer being the most prevalent example. Accordingly, tankyrase inhibitors have gained increasing attention as potential therapeutics. Since the discovery of XAV939 and IWR-1 as the first tankyrase inhibitors over two decades ago, tankyrase-targeted drug discovery has made significant progress. This review starts with an introduction of tankyrases, with emphasis placed on their cancer-related functions. Small-molecule inhibitors of tankyrases are subsequently delineated based on their distinct modes of binding to the enzymes. In addition to inhibitors that compete with oxidized nicotinamide adenine dinucleotide (NAD⁺) for binding to the catalytic domain of tankyrases, non-NAD⁺-competitive inhibitors are detailed. This is followed by a description of three clinically trialled tankyrase inhibitors. To conclude, some of challenges and prospects in developing tankyrase-targeted cancer therapies are discussed.

WNT as a Driver and Dependency in Cancer

The WNT signaling pathway is a critical regulator of development and adult tissue homeostasis and becomes dysregulated in many cancer types. Although hyperactivation of WNT signaling is common, the type and frequency of genetic WNT pathway alterations can vary dramatically between different cancers, highlighting possible cancer-specific mechanisms for WNT-driven disease. In this review, we discuss how WNT pathway disruption contributes to tumorigenesis in different organs and how WNT affects the tumor cell and immune microenvironment. Finally, we describe recent and ongoing efforts to target oncogenic WNT signaling as a therapeutic strategy. SIGNIFICANCE: WNT signaling is a fundamental regulator of tissue homeostasis and oncogenic driver in many cancer types. In this review, we highlight recent advances in our understanding of WNT signaling in cancer, particularly the complexities of WNT activation in distinct cancer types, its role in immune evasion, and the challenge of targeting the WNT pathway as a therapeutic strategy.

Tankyrase inhibitors as antitumor agents: a patent update (2013 - 2020)

INTRODUCTION

Tankyrase inhibitors gained significant attention as therapeutic targets in oncology because of their potency. Their primary role in inhibiting the Wnt signaling pathway makes them an important class of compounds with the potential to be used as a combination therapy in future treatments of colorectal cancer.

AREAS COVERED

This review describes pertinent work in the development of tankyrase inhibitors with a great emphasis on the recently patented TNKS inhibitors published from 2013 to 2020. This article also highlights a couple of promising candidates having tankyrase inhibitory effects and are currently undergoing clinical trials.

EXPERT OPINION

Following the successful clinical applications of PARP inhibitors, tankyrase inhibition has gained significant attention in the research community as a target with high therapeutic potential. The ubiquitous role of tankyrase in cellular homeostasis and Wnt-dependent tumor proliferation brought difficulties for researchers to strike the right balance between potency and on-target toxicity. The need for novel tankyrase inhibitors with a better ADMET profile can introduce an additional regimen in treating various malignancies in monotherapy or adjuvant therapy. The development of combination therapies, including tankyrase inhibitors with or without PARP inhibitory properties, can potentially benefit the larger population of patients with unmet medical needs.