The absence of class III β-tubulin is predictive of a favorable response to nab-paclitaxel and gemcitabine in patients with unresectable pancreatic ductal adenocarcinoma

The prognostic and predictive role of class III β-Tubulin and hENT1 expression in patients with advanced pancreatic ductal adenocarcinoma

BACKGROUND

FOLFIRINOX and gemcitabine-nabpaclitaxel (GnP) are standard first-line treatment regimens for advanced pancreatic ductal adenocarcinoma (PDAC). However, currently, there is a lack of predictive biomarkers to aid in the treatment selection. We aimed to explore the prognostic and predictive value of class III β-Tubulin (TUBB3) and human equilibrative nucleoside transporter 1 (hENT1) expression, which have previously been shown to be associated with taxane and gemcitabine resistance in advanced PDAC.

METHODS

We conducted a retrospective analysis of 106 patients with advanced PDAC treated with GnP and/or FOLFIRINOX at our institution. TUBB3 and hENT1 immunohistochemical staining was performed on tumor specimens and subsequently evaluated based on the intensity and percentage of expression.

RESULTS

In patients who received the GnP regimen, a high combined score (TUBB3low/hENT1high) was associated with a higher DCR and longer PFS compared to those with intermediate (TUBB3high/hENT1high or TUBB3low/hENT1low) and low score (TUBB3high/hENT1low). In the multivariate analysis, a high combined score was an independent predictor of higher DCR (OR:11.96; 95 % CI:2.61-54.82; p = 0.001) and longer PFS (HR:0.33; 95%CI:0.18-0.60; p < 0.001). However, there was no difference in response rates or PFS based on TUBB3 and hENT1 expression among patients receiving the FOLFIRINOX regimen.

CONCLUSION

Our findings indicate that tumor TUBB3 and hENT1 expression may predict the efficacy of the GnP regimen, and low TUBB3 and high hENT1 expression (TUBB3low/hENT1high) are associated with a higher DCR and longer PFS in patients treated with GnP. Evaluating TUBB3 and hENT1 jointly can identify the patients most (as well as least) likely to benefit from GnP chemotherapy.

Class III β-Tubulin Expression Is of Value in Selecting nab -Paclitaxel and Gemcitabine as First-Line Therapy in Unresectable Pancreatic Cancer

OBJECTIVES

Nab -paclitaxel and gemcitabine (GnP) or FOLFIRINOX (a combination of leucovorin, fluorouracil, irinotecan, and oxaliplatin [FFX]) is currently recognized as the standard first-line regimen for unresectable pancreatic ductal adenocarcinoma (PDAC). Class III β-tubulin (TUBB3) has the potential to predict resistance to taxane in various tumors; therefore, this study aimed to clarify whether TUBB3 is a predictive marker for GnP response.

METHODS

We retrospectively reviewed 113 patients with PDAC who received GnP or FFX as first-line chemotherapy and examined immunohistochemically the TUBB3 expression in specimens obtained by endoscopic ultrasound-guided fine-needle aspiration.

RESULTS

High TUBB3 expression was associated with a significantly lower disease control rate ( P = 0.017) and shorter progression-free survival (PFS) ( P = 0.019), and multivariate analysis revealed that TUBB3 expression was an independent variable for PFS in the GnP first-line group ( P = 0.045). In addition, in the FFX first-line group, TUBB3 expression was not correlated with PFS or overall survival (OS). In all 113 patients, TUBB3 expression was not also associated with OS.

CONCLUSIONS

Class III β-tubulin might be a predictive factor for the response of GnP, but not a prognostic factor for OS, helping the selection of an optimized first-line chemotherapy regimen for unresectable PDAC.

The Beta-Tubulin Isotype TUBB6 Controls Microtubule and Actin Dynamics in Osteoclasts

Osteoclasts are bone resorbing cells that participate in the maintenance of bone health. Pathological increase in osteoclast activity causes bone loss, eventually resulting in osteoporosis. Actin cytoskeleton of osteoclasts organizes into a belt of podosomes, which sustains the bone resorption apparatus and is maintained by microtubules. Better understanding of the molecular mechanisms regulating osteoclast cytoskeleton is key to understand the mechanisms of bone resorption, in particular to propose new strategies against osteoporosis. We reported recently that β-tubulin isotype TUBB6 is key for cytoskeleton organization in osteoclasts and for bone resorption. Here, using an osteoclast model CRISPR/Cas9 KO for Tubb6, we show that TUBB6 controls both microtubule and actin dynamics in osteoclasts. Osteoclasts KO for Tubb6 have reduced microtubule growth speed with longer growth life time, higher levels of acetylation, and smaller EB1-caps. On the other hand, lack of TUBB6 increases podosome life time while the belt of podosomes is destabilized. Finally, we performed proteomic analyses of osteoclast microtubule-associated protein enriched fractions. This highlighted ARHGAP10 as a new microtubule-associated protein, which binding to microtubules appears to be negatively regulated by TUBB6. ARHGAP10 is a negative regulator of CDC42 activity, which participates in actin organization in osteoclasts. Our results suggest that TUBB6 plays a key role in the control of microtubule and actin cytoskeleton dynamics in osteoclasts. Moreover, by controlling ARHGAP10 association with microtubules, TUBB6 may participate in the local control of CDC42 activity to ensure efficient bone resorption.

Personalized medicine of non-gene-specific chemotherapies for non-small cell lung cancer

Non-small cell lung cancer is recognized as the deadliest cancer across the globe. In some areas, it is more common in women than even breast and cervical cancer. Its rise, vaulted by smoking habits and increasing air pollution, has garnered much attention and resource in the medical field. The first lung cancer treatments were developed more than half a century ago. Unfortunately, many of the earlier chemotherapies often did more harm than good, especially when they were used to treat genetically unsuitable patients. With the introduction of personalized medicine, physicians are increasingly aware of when, how, and in whom, to use certain anti-cancer agents. Drugs such as tyrosine kinase inhibitors, anaplastic lymphoma kinase inhibitors, and monoclonal antibodies possess limited utility because they target specific oncogenic mutations, but other drugs that target mechanisms universal to all cancers do not. In this review, we discuss many of these non-oncogene-targeting anti-cancer agents including DNA replication inhibitors (i.e., alkylating agents and topoisomerase inhibitors) and cytoskeletal function inhibitors to highlight their application in the setting of personalized medicine as well as their limitations and resistance factors.

The plasticity of pancreatic cancer stem cells: implications in therapeutic resistance

The ever-growing perception of cancer stem cells (CSCs) as a plastic state rather than a hardwired defined entity has evolved our understanding of the functional and biological plasticity of these elusive components in malignancies. Pancreatic cancer (PC), based on its biological features and clinical evolution, is a prototypical example of a CSC-driven disease. Since the discovery of pancreatic CSCs (PCSCs) in 2007, evidence has unraveled their control over many facets of the natural history of PC, including primary tumor growth, metastatic progression, disease recurrence, and acquired drug resistance. Consequently, the current near-ubiquitous treatment regimens for PC using aggressive cytotoxic agents, aimed at ''tumor debulking'' rather than eradication of CSCs, have proven ineffective in providing clinically convincing improvements in patients with this dreadful disease. Herein, we review the key hallmarks as well as the intrinsic and extrinsic resistance mechanisms of CSCs that mediate treatment failure in PC and enlist the potential CSC-targeting 'natural agents' that are gaining popularity in recent years. A better understanding of the molecular and functional landscape of PCSC-intrinsic evasion of chemotherapeutic drugs offers a facile opportunity for treating PC, an intractable cancer with a grim prognosis and in dire need of effective therapeutic advances.

βIII-tubulin overexpression in cancer: Causes, consequences, and potential therapies

Class III β-tubulin (βIII-tubulin) is frequently overexpressed in human tumors and is associated with resistance to microtubule-targeting agents, tumor aggressiveness, and poor patient outcome. Understanding the mechanisms regulating βIII-tubulin expression and the varied functions βIII-tubulin may have in different cancers is vital to assess the prognostic value of this protein and to develop strategies to enhance therapeutic benefits in βIII-tubulin overexpressing tumors. Here we gather all the available evidence regarding the clinical implications of βIII-tubulin overexpression in cancer, describe factors that regulate βIII-tubulin expression, and discuss current understanding of the mechanisms underlying βIII-tubulin-mediated resistance to microtubule-targeting agents and tumor aggressiveness. Finally, we provide an overview of emerging therapeutic strategies to target tumors that overexpress βIII-tubulin.

Four-weekly Low-dose Gemcitabine and Paclitaxel in Patients With Platinum-resistant Urothelial Cancer and Performance Status 2/3

BACKGROUND/AIM

Immune check-point inhibitors are often unsuitable for patients with urothelial cancer with a poor performance status (PS 2 or 3). The aim of this study was to assess the safety and usefulness of combined therapy with low-dose gemcitabine and paclitaxel every 4 weeks.

PATIENTS AND METHODS

Thirty patients were treated with gemcitabine (700 mg/m² on day 1) and paclitaxel (70 mg/m² on day 1) every 4 weeks. The predictive value of human antigen-R (HuR) and class III β-tubulin (TUBB3) were also analyzed.

RESULTS

There was no severe adverse event nor significant decrease in quality of life. The survival period of patients treated with this regimen was significantly longer than that of those treated with best supportive care. The expression pattern of HuR negativity and TUBB3 positivity predicted significantly worse overall survival.

CONCLUSION

Our regimen was suitable as second-line therapy for patients with advanced platinum-resistant UC with a poor PS. However, a HuR-negative and TUBB3-positive expression pattern appears to confer poorer outcome.

Pharmacogenetics of treatments for pancreatic cancer

Introduction: Despite clinical efforts, pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. The scarcity of effective therapies can be reflected by the lack of reliable biomarkers to adapt anticancer drugs prescription to tumors' and patients' features. Areas covered: Pharmacogenetics should provide the way to select patients who may benefit from a specific therapy that best matches individual and tumor genetic profile, but it has not yet led to gains in outcome. This review describes PDAC pharmacogenetics findings, critically reappraising studies on polymorphisms and -omics profiles correlated to response to gemcitabine, FOLFIRINOX, and nab-paclitaxel combinations, as well as limitations of targeted therapies. Further, we question whether personalized approaches will benefit patients to any significant degree, supporting the need of new strategies within well-designed trials and validated genomic tests for treatment decision-making. Expert opinion: A major challenge in PDAC is the identification of subgroups of patients who will benefit from treatments. Minimally-invasive tests to analyze biomarkers of drug sensitivity/toxicity should be developed alongside anticancer treatments. However, progress might fall below expectations because of tumor heterogeneity and clonal evolution. Whole-genome sequencing and liquid biopsies, as well as prospective validation in selected cohorts, should overcome the limitations of traditional pharmacogenetic approaches.

Crystal Structure of the Cyclostreptin-Tubulin Adduct: Implications for Tubulin Activation by Taxane-Site Ligands

It has been proposed that one of the mechanisms of taxane-site ligand-mediated tubulin activation is modulation of the structure of a switch element (the M-loop) from a disordered form in dimeric tubulin to a folded helical structure in microtubules. Here, we used covalent taxane-site ligands, including cyclostreptin, to gain further insight into this mechanism. The crystal structure of cyclostreptin-bound tubulin reveals covalent binding to βHis229, but no stabilization of the M-loop. The capacity of cyclostreptin to induce microtubule assembly compared to other covalent taxane-site agents demonstrates that the induction of tubulin assembly is not strictly dependent on M-loop stabilization. We further demonstrate that most covalent taxane-site ligands are able to partially overcome drug resistance mediated by βIII-tubulin (βIII) overexpression in HeLa cells, and compare their activities to pironetin, an interfacial covalent inhibitor of tubulin assembly that displays invariant growth inhibition in these cells. Our findings suggest a relationship between a diminished interaction of taxane-site ligands with βIII-tubulin and βIII tubulin-mediated drug resistance. This supports the idea that overexpression of βIII increases microtubule dynamicity by counteracting the enhanced microtubule stability promoted by covalent taxane-site binding ligands.

The Use of Star Polymer Nanoparticles for the Delivery of siRNA to Mouse Orthotopic Pancreatic Tumor Models

Pancreatic cancer is a lethal malignancy which is refractory to most chemotherapy drugs. Recent landmark studies have shed new light on the complex genetic heterogeneity of pancreatic cancer and provide an opportunity to utilize "precision-based medicines" to target genes based on the genetic profile of an individual's tumor to increase the efficiency of chemotherapy and decrease tumor growth and metastases. Gene-silencing drugs in the form of short-interfering RNA (siRNA) have the potential to play an important role in precision medicine for pancreatic cancer by silencing the expression of genes including those considered difficult to inhibit (undruggable) using chemical agents. However, before siRNA can reach its clinical potential a delivery vehicle is needed to carry siRNA across the cell membrane and into the cytoplasm of the cell. Herein, we detail the methods required to use star polymer nanoparticles to deliver siRNA to pancreatic tumors in an orthotopic pancreatic cancer mouse model to silence the expression of an "undruggable" gene (βIII-tubulin) that regulates pancreatic cancer growth and chemosensitivity.

Retrospective analysis of efficacy and safety of Gemcitabine-based chemotherapy in patients with metastatic pancreatic adenocarcinoma experiencing disease progression on FOLFIRINOX

Background

Metastatic pancreatic adenocarcinoma (MPA) represents a highly lethal condition. Despite the improvements seen with FOLFIRINOX, there is no randomized data to guide treatment selection beyond this regimen. We aimed to evaluate the outcomes of patients with MPA progressing on FOLFIRINOX who were treated with Gemcitabine-based chemotherapy afterwards.

Methods

We included patients aged 18 years or older, treated for MPA with FOLFIRINOX in the first-line setting and who experienced disease progression, with Eastern Cooperative Oncology Group (ECOG) performance status 0-2, and treated with at least one cycle of Gemcitabine-based chemotherapy in second or further lines of treatment. We used descriptive statistics to characterize the study population and Cox proportional-hazards models to describe factors associated with survival. As an exploratory analysis, we compared the outcomes of patients treated with single-agent Gemcitabine with those of patients undergoing Gemcitabine-based polychemotherapy.

Results

The study population consisted of 42 patients. Median age was 59 years and 78.6% of patients presented ECOG 0-1. Thirty-three patients (78.6%) were treated with Gemcitabine-based chemotherapy in the second-line setting and 27 patients (64.3%) were treated with single-agent Gemcitabine. Objective response rate and disease control rate were 2.4% and 33.4%, respectively. Median progression-free survival (PFS) and median overall survival (OS) were 2.9 and 5.5 months, respectively. Six-month PFS and OS rates were 19.2% and 46.2%, respectively. We observed no significant difference in OS according to the type of Gemcitabine-based chemotherapy, despite numerically improved disease control rate and PFS for those treated with Gemcitabine-based polychemotherapy. In multivariate analysis, ECOG 2 (vs. ECOG 0-1) was the only factor significantly associated with inferior PFS and OS.

Conclusions

a subgroup of patients with MPA derives benefit from treatment with Gemcitabine-based regimens after FOLFIRINOX. There is a suggestion that Gemcitabine-based combinations, in particular Gemcitabine plus Nab-Paclitaxel, provide superior outcomes compared to single-agent Gemcitabine. Additionally, treatment in this setting should be offered carefully to patients with ECOG 2, as they present shorter survival and increased risk of toxicity.