Intravenous paclitaxel is specifically retained in human gynecologic carcinoma tissues in vivo

CENP-E Inhibition Induces Chromosomal Instability and Synergizes with Diverse Microtubule-Targeting Agents in Breast Cancer

Drugs that perturb microtubules are commonly used to treat breast cancers of all subtypes in both early stage and metastatic disease, but they are effective in only approximately 50% of patients. High concentrations of microtubule-targeting agents can elicit mitotic arrest in cell culture models; however, recent evidence from primary and metastatic breast cancers has revealed that these agents only accumulate at intratumoral levels capable of inducing abnormal multipolar mitotic spindles, not mitotic arrest. Although the maintenance of multipolar spindles can generate cytotoxic rates of chromosomal instability (CIN), focusing of aberrant multipolar spindles into normal bipolar spindles can dramatically reduce CIN and confer resistance to microtubule poisons. Here, we showed that inhibition of the mitotic kinesin centromeric-associated protein-E (CENP-E) overcomes resistance caused by focusing multipolar spindles. Clinically relevant microtubule-targeting agents used a mechanistically conserved pathway to induce multipolar spindles without requiring centrosome amplification. Focusing could occur at any point in mitosis, with earlier focusing conferring greater resistance to antimicrotubule agents. CENP-E inhibition increased CIN on focused spindles by generating chromosomes that remained misaligned at spindle poles during anaphase, which substantially increased death in the resulting daughter cells. CENP-E inhibition synergized with diverse, clinically relevant microtubule poisons to potentiate cell death in cell lines and suppress tumor growth in orthotopic tumor models. These results suggest that primary resistance to microtubule-targeting drugs can be overcome by simultaneous inhibition of CENP-E. Significance: The increased incidence of polar chromosomes induced by inhibition of the mitotic kinesin CENP-E exacerbates chromosomal instability, reduces daughter cell viability, and improves sensitivity to microtubule-targeting therapies.

Rationale for combination of paclitaxel and CDK4/6 inhibitor in ovarian cancer therapy - non-mitotic mechanisms of paclitaxel

Taxanes and CDK4/6 inhibitors (CDK4/6i) are two families of successful anti-mitotic drugs used in the treatment of solid tumors. Paclitaxel, representing taxane compounds, has been used either alone or in combination with other agents (commonly carboplatin/cisplatin) in the treatment of many solid tumors including ovarian, breast, lung, prostate cancers, and Kaposi's sarcoma. Paclitaxel has been routinely prescribed in cancer treatment since the 1990s, and its prominent role is unlikely to be replaced in the foreseeable future. Paclitaxel and other taxanes work by binding to and stabilizing microtubules, causing mitotic arrest, aberrant mitosis, and cell death. CDK4/6i (palbociclib, ribociclib, abemaciclib) are relatively new cell cycle inhibitors that have been found to be effective in breast cancer treatment, and are currently being developed in other solid tumors. CDK4/6i blocks cell cycle progression at the G1 phase, resulting in cell death by mechanisms not yet fully elucidated. At first glance, paclitaxel and CDK4/6i are unlikely synergistic agents as both are cell cycle inhibitors that work at different phases of the cell cycle, and few clinical trials have yet considered adding CDK4/6i to existing paclitaxel chemotherapy. However, recent findings suggest the importance of a non-mitotic mechanism of paclitaxel in cancer cell death and pre-clinical data support rationale for a strategic paclitaxel and CDK4/6i combination. In mouse tumor model studies, drug sequencing resulted in differential efficacy, indicating complex biological interactions of the two drugs. This article reviews the rationales of combining paclitaxel with CDK4/6i as a potential therapeutic option in recurrent ovarian cancer.

Low Intensity Ultrasound as an Antidote to Taxane/Paclitaxel-induced Cytotoxicity

The taxane family of compounds, including Taxol/paclitaxel and Taxotere/docetaxel, are surprisingly successful drugs used in combination or alone for the treatment of most major solid tumors, especially metastatic cancer. The drugs are commonly used in regimen with other agents (often platinum drugs) as frontline treatment, or used as a single agent in a dose dense regimen for recurrent cancer. The major side effects of taxanes are peripheral neuropathy, alopecia, and neutropenia, which are grave burden for patients and limit the full potential of the taxane drugs. Especially in the current treatment protocol for peripheral neuropathy, taxane dosage is reduced once the symptoms present, resulting in the loss of full or optimal cancer killing activity.

Substantial efforts have been made to address the problem of cytotoxic side effects of taxanes, though strategies remain very limited. Following administration of the taxane compound by infusion, taxane binds to cellular microtubules and is sequestered within the cells for several days. Taxane stabilizes and interferes with microtubule function, leading to ultimate death of cancer cells, but also damages hair follicles, peripheral neurons, and hemopoietic stem cells. Currently, cryo-treatment is practiced to limit exposure and side effects of the drug during infusion, though the effectiveness is uncertain or limited.

A recent laboratory finding may provide a new strategy to counter taxane cytotoxicity, that a brief exposure to low density ultrasound waves was sufficient to eliminate paclitaxel cytotoxicity cells in culture by transiently breaking microtubule filaments, which were then relocated to lysosomes for disposal. Thus, ultrasonic force to break rigid microtubules is an effective solution to counter taxane cytotoxicity. The discovery and concept of low intensity ultrasound as an antidote may have the potential to provide a practical strategy to counter paclitaxel-induced peripheral neuropathy and alopecia that resulted from chemotherapy.

Taxanes are a class of important drugs used in chemotherapy to treat several major cancers. This article reviews a new laboratory discovery that ultrasound can be used as an antidote for the peripheral cytotoxicity of taxane drugs and discusses the potential development and application of low intensity ultrasound to prevent side effects in chemotherapeutic treatment of cancer patients.

Comparison of outcomes and side effects for neoadjuvant chemotherapy with weekly cisplatin and paclitaxel followed by chemoradiation vs. chemoradiation alone in stage IIB-IVA cervical cancer: study protocol for a randomized controlled trial

Background

Currently, the standard treatment for locally advanced cervical cancer is concurrent chemoradiation (CCRT). The effect of neoadjuvant chemotherapy in advanced cervical cancer is controversial. Studies have shown that the addition of a weekly regimen of neoadjuvant chemotherapy (NACT) followed by CCRT may be superior to a thrice-weekly regimen of NACT and CCRT. Among patients who had not received prior cisplatin, a cisplatin and paclitaxel (TP) regimen resulted in longer overall survival than other regimens. This study aims to investigate the feasibility, safety, and efficacy of NACT with weekly TP followed by CCRT.

Methods

This is a prospective, randomized, open-labeled, multicentered phase III study. Based on a 65% of 2-year disease-free survival (DFS) rate in the CCRT group and 80% of that in NACT followed by CCRT group, and on prerequisite conditions including an 8% loss to follow-up, a two-sided 5% of type I error probability, and an 80% of power, a total of 300 cases were required for enrollment. Patients with IIB–IVA cervical cancer will be randomly allocated in a 1:1 ratio to one of two intervention arms. In the study arm, patients will receive dose-dense cisplatin (40 mg/m²) and paclitaxel (60 mg/m²) weekly for 4 cycles followed by CCRT (45 Gy in 5 weeks concurrent with cisplatin 40 mg/m² weekly) plus image-guided adaptive brachytherapy (IGBRT). In the control arm, patients will undergo CCRT treatment. The primary endpoint of the study is 2-year disease-free survival (DFS); the secondary endpoints are 5-year overall survival (OS) and disease-free survival (DFS), the response rate 3 months after treatment completion, grade III/IV adverse effects, and quality of life, and potential biomarkers for predicting treatment response will also be studied.

Discussion

The data gathered from the study will be used to determine whether NACT with weekly TP followed by CCRT may become an optimized treatment for locally advanced cervical cancer.

Trial registration

Chinese Clinical Trial Registry ChiCTR1900025327. Registered on 24 August 2019. medresman.org.cn ChiCTR1900025326

Breaking malignant nuclei as a non-mitotic mechanism of taxol/paclitaxel

Discovered in a large-scale screening of natural plant chemicals, Taxol/paclitaxel and the taxane family of compounds are surprisingly successful anti-cancer drugs, used in treatment of the majority of solid tumors, and especially suitable for metastatic and recurrent cancer. Paclitaxel is often used in combination with platinum agents and is administrated in a dose dense regimen to treat recurrent cancer. The enthusiasm and clinical development were prompted by the discovery that Taxol binds beta-tubulins specifically found within microtubules and stabilizes the filaments, and consequently inhibits mitosis. However, questions on how paclitaxel suppresses cancer persist, as other specific mitotic inhibitors are impressive in pre-clinical studies but fail to achieve significant clinical activity. Thus, additional mechanisms, such as promoting mitotic catastrophe and impacting non-mitotic targets, have been proposed and studied. A good understanding of how paclitaxel, and additional new microtubule stabilizing agents, kill cancer cells will advance the clinical application of these common chemotherapeutic agents. A recent study provides a potential non-mitotic mechanism of paclitaxel action, that paclitaxel-induced rigid microtubules act to break malleable cancer nuclei into multiple micronuclei. Previous studies have established that cancer cells have a less sturdy, more pliable nuclear envelope due to the loss or reduction of lamin A/C proteins. Such changes in nuclear structure provide a selectivity for paclitaxel to break the nuclear membrane and kill cancer cells over non-neoplastic cells that have a sturdier nuclear envelope. The formation of multiple micronuclei appears to be an important aspect of paclitaxel in the killing of cancer cells, either by a mitotic or non-mitotic mechanism. Additionally, by binding to microtubule, paclitaxel is readily sequestered and concentrated within cells. This unique pharmacokinetic property allows the impact of paclitaxel on cells to persist for several days, even though the circulating drug level is much reduced following drug administration/infusion. The retention of paclitaxel within cells likely is another factor contributing to the efficacy of the drugs. Overall, the new understanding of Taxol/paclitaxel killing mechanism-rigid microtubule-induced multiple micronucleation-will likely provide new strategies to overcome drug resistance and for rational drug combination.

Living in CIN: Mitotic Infidelity and Its Consequences for Tumor Promotion and Suppression

Errors in chromosome segregation during mitosis have been recognized as a hallmark of tumor cells since the late 1800s, resulting in the long-standing hypothesis that mitotic abnormalities drive tumorigenesis. Recent work has shown that mitotic defects can promote tumors, suppress them, or do neither, depending on the rate of chromosome missegregation. Here we discuss the causes of chromosome missegregation, their effects on tumor initiation and progression, and the evidence that increasing the rate of chromosome missegregation may be an effective chemotherapeutic strategy.

How Taxol/paclitaxel kills cancer cells

Taxol (generic name paclitaxel) is a microtubule-stabilizing drug that is approved by the Food and Drug Administration for the treatment of ovarian, breast, and lung cancer, as well as Kaposi's sarcoma. It is used off-label to treat gastroesophageal, endometrial, cervical, prostate, and head and neck cancers, in addition to sarcoma, lymphoma, and leukemia. Paclitaxel has long been recognized to induce mitotic arrest, which leads to cell death in a subset of the arrested population. However, recent evidence demonstrates that intratumoral concentrations of paclitaxel are too low to cause mitotic arrest and result in multipolar divisions instead. It is hoped that this insight can now be used to develop a biomarker to identify the ∼50% of patients that will benefit from paclitaxel therapy. Here I discuss the history of paclitaxel and our recently evolved understanding of its mechanism of action.

The pharmacological point of view of resistance to therapy in tumors

Resistance to therapy is a challenging clinical problem, whose solution is far from being reached. Gains in current knowledge have identified key elements at the basis of drug resistance and have suggested possible ways to overcome it. However, some points have always to be kept in mind whatever the type of tumor or drug (cytotoxic or targeted agent) when considering treatment resistance in tumors. In this review we discuss these points and their impact in resistance to cancer therapy: the importance of reaching active tumor drug concentration, reviewing the various micro- and macro-components of the host that can influence their concentrations and activity, the evolving complex heterogeneity of tumors, the intrinsic tumor cell susceptibility to the drug, and the emerging role of the tumor microenvironment. Both the data from the molecular and biological characterization of human tumors allow a better rational and timing use of the available arsenal of anticancer therapy and new strategies to improve the penetration of antitumor drugs in tumors are the new chances to delay and possibly eliminate the emergence of resistance in tumors.

Targeting MDR in breast and lung cancer: discriminating its potential importance from the failure of drug resistance reversal studies

This special issue of Drug Resistance Updates is dedicated to multidrug resistance protein 1 (MDR-1), 35 years after its discovery. While enormous progress has been made and our understanding of drug resistance has become more sophisticated and nuanced, after 35 years the role of MDR-1 in clinical oncology remains a work in progress. Despite clear in vitro evidence that P-glycoprotein (Pgp), encoded by MDR-1, is able to dramatically reduce drug concentrations in cultured cells, and that drug accumulation can be increased by small molecule inhibitors, clinical trials testing this paradigm have mostly failed. Some have argued that it is no longer worthy of study. However, repeated analyses have demonstrated MDR-1 expression in a tumor is a poor prognostic indicator leading some to conclude MDR-1 is a marker of a more aggressive phenotype, rather than a mechanism of drug resistance. In this review we will re-evaluate the MDR-1 story in light of our new understanding of molecular targeted therapy, using breast and lung cancer as examples. In the end we will reconcile the data available and the knowledge gained in support of a thesis that we understand far more than we realize, and that we can use this knowledge to improve future therapies.