The role of maintenance therapy following autologous stem cell transplantation in newly diagnosed multiple myeloma: Considerations on behalf of the Chronic Malignancies Working Party of the EBMT

Recent treatment advancements in multiple myeloma have led to significant improvements in patient outcomes. Maintenance therapy following autologous haematopoietic stem cell transplantation (AHCT) is now standard of care and has been demonstrated to prolong and deepen treatment responses. Currently, lenalidomide remains the single agent that has been approved for maintenance post-AHCT in Europe and the USA which, if tolerated, is continued until disease progression. The treatment landscape is rapidly expanding however, and the optimal personalised maintenance approach for a patient is becoming more complex. Treatment outcomes for patients with high-risk disease remain poor and choice of maintenance in this population also remains unclear. This review article evaluates up-to-date literature regarding established maintenance approaches. It further analyses ongoing studies exploring maintenance regimens using combination and novel agents, approaches to maintenance in patients with cytogenetic high-risk disease and minimal residual disease response-adapted strategies that reflect the current evolving treatment paradigm.

IL-6 levels dominate the serum cytokine signature of severe epidermolysis bullosa: A prospective cohort study

BACKGROUND

Systemic inflammation is considered a major player in the pathogenesis of epidermolysis bullosa (EB), but its pattern has only been described in small heterogeneous cohorts. There is controversy if and how systemic inflammation should be therapeutically targeted.

METHODS

We examined serum proinflammatory, anti-inflammatory, and itch related cytokines in a paediatric cohort of 29 patients with junctional and dystrophic EB. The cytokine that emerged as the most relevant was measured in a validation cohort of 42 patients during follow-up visits over 2 years.

RESULTS

IL-6 showed the most consistent and highest aberration dominating systemic inflammation. IL-6 correlated with wound body surface area (BSA) in both, finding and validation cohorts. Patients with less than 3% wound BSA had normal IL-6, while IL-6 levels significantly increased at more than 5% and 10% of wound BSA. TGF-β was only marginally elevated in patients with severe recessive dystrophic EB, while TNF-α, IFN-γ and IL-1β varied inconsistently. Patients reporting itch showed elevations in type 2 immunity (IgE, TSLP, IL4 and/or IL-31, respectively).

CONCLUSIONS

Our data suggest a dominant skin barrier and wound healing inflammatory pattern in junctional and dystrophic EB that depends on the wound area and not on the EB type. In EB, itch mediators may be similar to other pruritic disorders.

Meeting Summary: Global Vaccine and Immunization Research Forum, 2021

The 2021 Global Vaccine and Immunization Research Forum highlighted the considerable advances and recent progress in research and development for vaccines and immunization, critically reviewed lessons learned from COVID-19 vaccine programs, and looked ahead to opportunities for this decade. For COVID-19, decades of investments in basic and translational research, new technology platforms, and vaccines targeting prototype pathogens enabled a rapid, global response. Unprecedented global coordination and partnership have played an essential role in creating and delivering COVID-19 vaccines. More improvement is needed in product attributes such as deliverability, and in equitable access to vaccines. Developments in other priority areas included: the halting of two human immunodeficiency virus vaccine trials due to lack of efficacy in preventing infection; promising efficacy results in Phase 2 trials of two tuberculosis vaccines; pilot implementation of the most advanced malaria vaccine candidate in three countries; trials of human papillomavirus vaccines given in single-dose regimens; and emergency use listing of a novel, oral poliomyelitis type 2 vaccine. More systematic, proactive approaches are being developed for fostering vaccine uptake and demand, aligning on priorities for investment by the public and private sectors, and accelerating policy making. Participants emphasized that addressing endemic disease is intertwined with emergency preparedness and pandemic response, so that advances in one area create opportunities in the other. In this decade, advances made in response to the COVID-19 pandemic should accelerate availability of vaccines for other diseases, contribute to preparedness for future pandemics, and help to achieve impact and equity under Immunization Agenda 2030.

Accelerating access for all through research and innovation in immunization: Recommendations from Strategic Priority 7 of the Immunization Agenda 2030

Research and innovation have been fundamental to many of the successes in immunization thus far, and will play important roles in the future success of Immunization Agenda 2030 (IA2030). Strategic Priority 7 (SP7) of IA2030, which addresses research and innovation, is explicitly informed by country needs and priorities, and aims to strengthen the innovation ecosystem through capacity building and collaboration at country, regional, and global levels. SP7 identifies four key focus areas: (1) "needs-based innovation", (2) "new and improved products, services, and practices", (3) "evidence for implementation", and (4) "local capacity". Strategic interventions in these key focus areas apply the lessons of the Global Vaccine Action Plan and the "Decade of Vaccines" to emphasize local innovation, promote the use of research by countries to improve program performance and impact, and encourage capacity building for the development and implementation of innovations. The proposed approach will maintain a focus on the development of new vaccines and the improvement of existing vaccines, and increase attention to innovation in service delivery. Monitoring and evaluation will foster evidence-based priority setting at the country level and help to ground the global research and development (R&D) agenda in the needs of communities. Together, these approaches are intended to harness the power of research and innovation more effectively, to meet the challenges of the future and achieve the ambitious goals of IA2030.

Improving access to human papillomavirus vaccines: A case study in the IA2030 core principle of partnership

Partnerships are fundamental to progress in immunization, and this is especially true for human papillomavirus (HPV) vaccination, which must be delivered in the context of a broader immunization, sexual and reproductive health, and cervical cancer prevention programs. Starting from the discovery and development of HPV vaccines, through to implementation and improvement of the program's resilience, partnerships have played a critical role. In May 2018, the Global Strategy to Accelerate the Elimination of Cervical Cancer set a target for 90 % of girls to be fully vaccinated with HPV vaccine by age 15 years. This will require effective partnership and multisectoral collaboration among current and future partners to ensure alignment of interests, efficient execution, and the establishment of mechanisms to resolve emerging challenges and pre-empt foreseeable risks. In ramping up this partnering approach, HPV can provide a template for other health and immunization programs.

Pharmacogenomics cascade testing (PhaCT): a novel approach for preemptive pharmacogenomics testing to optimize medication therapy

The implementation of pharmacogenomics (PGx) has come a long way since the dawn of utilizing pharmacogenomic data in clinical patient care. However, the potential benefits of sharing PGx results have yet to be explored. In this paper, we explore the willingness of patients to share PGx results, as well as the inclusion of family medication history in identifying potential family members for pharmacogenomics cascade testing (PhaCT). The genetic similarities in families allow for identifying potential gene variants prior to official preemptive testing. Once a candidate patient is determined, PhaCT can be initiated. PhaCT recognizes that further cascade testing throughout a family can serve to improve precision medicine. In order to make PhaCT feasible, we propose a novel shareable HIPAA-compliant informatics platform that will enable patients to manage not only their own test results and medications but also those of their family members. The informatics platform will be an external genomics system with capabilities to integrate with patients' electronic health records. Patients will be given the tools to provide information to and work with clinicians in identifying family members for PhaCT through this platform. Offering patients the tools to share PGx results with their family members for preemptive testing could be the key to empowering patients. Clinicians can utilize PhaCT to potentially improve medication adherence, which may consequently help to distribute the burden of health management between patients, family members, providers, and payers.

Artificial Intelligence-Powered Smartphone App to Facilitate Medication Adherence: Protocol for a Human Factors Design Study

BACKGROUND

Medication Guides consisting of crucial interactions and side effects are extensive and complex. Due to the exhaustive information, patients do not retain the necessary medication information, which can result in hospitalizations and medication nonadherence. A gap exists in understanding patients' cognition of managing complex medication information. However, advancements in technology and artificial intelligence (AI) allow us to understand patient cognitive processes to design an app to better provide important medication information to patients.

OBJECTIVE

Our objective is to improve the design of an innovative AI- and human factor-based interface that supports patients' medication information comprehension that could potentially improve medication adherence.

METHODS

This study has three aims. Aim 1 has three phases: (1) an observational study to understand patient perception of fear and biases regarding medication information, (2) an eye-tracking study to understand the attention locus for medication information, and (3) a psychological refractory period (PRP) paradigm study to understand functionalities. Observational data will be collected, such as audio and video recordings, gaze mapping, and time from PRP. A total of 50 patients, aged 18-65 years, who started at least one new medication, for which we developed visualization information, and who have a cognitive status of 34 during cognitive screening using the TICS-M test and health literacy level will be included in this aim of the study. In Aim 2, we will iteratively design and evaluate an AI-powered medication information visualization interface as a smartphone app with the knowledge gained from each component of Aim 1. The interface will be assessed through two usability surveys. A total of 300 patients, aged 18-65 years, with diabetes, cardiovascular diseases, or mental health disorders, will be recruited for the surveys. Data from the surveys will be analyzed through exploratory factor analysis. In Aim 3, in order to test the prototype, there will be a two-arm study design. This aim will include 900 patients, aged 18-65 years, with internet access, without any cognitive impairment, and with at least two medications. Patients will be sequentially randomized. Three surveys will be used to assess the primary outcome of medication information comprehension and the secondary outcome of medication adherence at 12 weeks.

RESULTS

Preliminary data collection will be conducted in 2021, and results are expected to be published in 2022.

CONCLUSIONS

This study will lead the future of AI-based, innovative, digital interface design and aid in improving medication comprehension, which may improve medication adherence. The results from this study will also open up future research opportunities in understanding how patients manage complex medication information and will inform the format and design for innovative, AI-powered digital interfaces for Medication Guides.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/21659.

The inclusion of health data standards in the implementation of pharmacogenomics systems: a scoping review

Background: Despite potential benefits, the practice of incorporating pharmacogenomics (PGx) results in clinical decisions has yet to diffuse widely. In this study, we conducted a review of recent discussions on data standards and interoperability with a focus on sharing PGx test results among health systems. Materials & methods: We conducted a literature search for PGx clinical decision support systems between 1 January 2012 and 31 January 2020. Thirty-two out of 727 articles were included for the final review. Results: Nine of the 32 articles mentioned data standards and only four of the 32 articles provided solutions for the lack of interoperability. Discussions: Although PGx interoperability is essential for widespread implementation, a lack of focus on standardized data creates a formidable challenge for health information exchange. Conclusion: Standardization of PGx data is essential to improve health information exchange and the sharing of PGx results between disparate systems. However, PGx data standards and interoperability are often not addressed in the system-level implementation.

Choosing Evolution over Extinction: Integrating Direct Patient Care Services and Value-Based Payment Models into the Community-Based Pharmacy Setting

The American healthcare payment model introduced Pharmacy Benefit Managers (PBMs) into a position of power that currently puts into question the state of the pharmacy profession, especially in the community field. Reimbursement plans had been designed to benefit all stakeholders and save patients money but have only been shown to increase costs for these involved parties. There exist unresolved gaps in care as a result of the healthcare structure and underutilized skills of trained pharmacists who do not have the federal means to provide clinical services. Four collaborative payment models have been proposed, offering methods to quell the monetary problems that exist and are predicted to continue with the closure of community pharmacies and sustained influence of PBMs. These models may additionally allow the expansion of pharmacy career paths and improve healthcare benefits for patients. With a reflective perspective on the healthcare structure and knowledge of positive impacts with the inclusion of pharmacists, solutions to payment challenges could present a progressive approach to an outdated system. The impact of the COVID-19 pandemic highlights a dependency on pharmacists and community settings. This outlook on pharmacists may persist and an established expansion of services could prove beneficial to all healthcare stakeholders.

Global Vaccine Action Plan lessons learned III: Monitoring and evaluation/accountability framework

INTRODUCTION

The Monitoring & Evaluation/Accountability (M&E/A) framework of the Global Vaccine Action Plan (GVAP) was used to report progress annually to the World Health Assembly (WHA).

METHODS

Stakeholder feedback was obtained through five reviews consisting of surveys and semi-structured interviews conducted from 2017 to 2019. Participants consisted of individuals involved in the development and implementation of GVAP or its M&E/A process, national immunization managers, academics, representatives of non-governmental organizations, and civil society organizations.

RESULTS

The feedback was mixed and contradictory for some components, though most participants reported that the M&E/A process was a highlight of GVAP and a step in the right direction. Several of the goals and targets were considered aspirational and unrealistic for many countries. There were mixed responses on whether it promoted accountability, especially at the country level.

DISCUSSION

The mixed and contradictory views on the M&E/A processes and its impact suggested a failure of communication about its scope and intent. Though the process, especially the annual reporting to the WHA, kept immunization high on the global agenda, it failed to fully meet the expectations in promoting accountability. Engaging with countries to capture the local context in setting global goals and targets and promoting local M&E/A processes will be important to achieve accountability in the next decade.

Eliminating Meningococcal Epidemics From the African Meningitis Belt: The Case for Advanced Prevention and Control Using Next-Generation Meningococcal Conjugate Vaccines

The introduction and rollout of a meningococcal serogroup A conjugate vaccine, MenAfriVac, in the African meningitis belt has eliminated serogroup A meningococcal infections for >300 million Africans. However, serogroup C, W, and X meningococci continue to circulate and have been responsible for focal epidemics in meningitis belt countries. Affordable multivalent meningococcal conjugate vaccines are being developed to prevent these non-A epidemics. This article describes the current epidemiologic situation and status of vaccine development and highlights questions to be addressed to most efficiently use these new vaccines.

Meeting report: Global vaccine and immunization research forum, 2018

Every two years, the Global Vaccine and Immunization Research Forum takes stock of global research in vaccines and immunization. As in prior years, the 2018 meeting addressed vaccine discovery, development, decision-making, and deployment. This time, however, it also featured two overarching themes: "Innovating for Equity" and "End-to-End Integration." Significant advances have been made in the last two years, but participants noted that some important goals of the Global Vaccine Action Plan are not being met and called urgently for innovation in improving access to vaccines. Two factors were highlighted as crucial to improving coverage: a focus on equity and sustainability throughout the immunization ecosystem, and an enabling political environment that prioritizes health and immunization.

Meeting report: Global vaccine and immunization research forum

Building on the success of the first Global Vaccine and Immunization Research Forum (GVIRF), the World Health Organization, the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health in the United States of America, and the Bill & Melinda Gates Foundation convened the second GVIRF in March 2016. Leading scientists, vaccine developers, and public health officials from around the world discussed scientific advances and innovative technologies to design and deliver vaccines as well as novel tools and approaches to increase the uptake of vaccines throughout the world. This report summarizes the discussions and conclusions from the forum participants.

Global Vaccine and Immunization Research Forum: Opportunities and challenges in vaccine discovery, development, and delivery

The World Health Organization, the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, and the Bill & Melinda Gates Foundation convened the first Global Vaccine and Immunization Research Forum (GVIRF) in March 2014. This first GVIRF aimed to track recent progress of the Global Vaccine Action Plan research and development agenda, identify opportunities and challenges, promote partnerships in vaccine research, and facilitate the inclusion of all stakeholders in vaccine research and development. Leading scientists, vaccine developers, and public health officials from around the world discussed scientific and technical challenges in vaccine development, research to improve the impact of immunization, and regulatory issues. This report summarizes the discussions and conclusions from the forum participants.

Complexity perplexity: a systematic review to describe the measurement of medication regimen complexity

INTRODUCTION

Complex medication regimens are error prone and challenging for patients, which may impact medication adherence and safety. No universal method to assess the complexity of medication regimens (CMRx) exists. The authors aim to review literature for CMRx measurements to establish consistencies and, secondarily, describe CMRx impact on healthcare outcomes.

AREAS COVERED

A search of EMBASE and PubMed for studies analyzing at least two medications and complexity components, among those self-managing medications, was conducted. Out of 1204 abstracts, 38 studies were included in the final sample. The majority (74%) of studies used one of five validated CMRx scales; their components and scoring were compared.

EXPERT OPINION

Universal CMRx assessment is needed to identify and reduce complex regimens, and, thus, improve safety. The authors highlight commonalities among five scales to help build consensus. Common components (i.e., regimen factors) included dosing frequency, units per dose, and non-oral routes. Elements (e.g., twice daily) of these components (e.g., dosing frequency) and scoring varied. Patient-specific factors (e.g., dexterity, cognition) were not addressed, which is a shortcoming of current scales and a challenge for future scales. As CMRx has important outcomes, notably adherence and healthcare utilization, a standardized tool has potential for far-reaching clinical, research, and patient-safety impact.

Surface charge and cellular processing of covalently functionalized multiwall carbon nanotubes determine pulmonary toxicity

Functionalized carbon nanotubes (f-CNTs) are being produced in increased volume because of the ease of dispersion and maintenance of the pristine material physicochemical properties when used in composite materials as well as for other commercial applications. However, the potential adverse effects of f-CNTs have not been quantitatively or systematically explored. In this study, we used a library of covalently functionalized multiwall carbon nanotubes (f-MWCNTs), established from the same starting material, to assess the impact of surface charge in a predictive toxicological model that relates the tubes' pro-inflammatory and pro-fibrogenic effects at cellular level to the development of pulmonary fibrosis. Carboxylate (COOH), polyethylene glycol (PEG), amine (NH2), sidewall amine (sw-NH2), and polyetherimide (PEI)-modified MWCNTs were successfully established from raw or as-prepared (AP-) MWCNTs and comprehensively characterized by TEM, XPS, FTIR, and DLS to obtain information about morphology, length, degree of functionalization, hydrodynamic size, and surface charge. Cellular screening in BEAS-2B and THP-1 cells showed that, compared to AP-MWCNTs, anionic functionalization (COOH and PEG) decreased the production of pro-fibrogenic cytokines and growth factors (including IL-1β, TGF-β1, and PDGF-AA), while neutral and weak cationic functionalization (NH2 and sw-NH2) showed intermediary effects. In contrast, the strongly cationic PEI-functionalized tubes induced robust biological effects. These differences could be attributed to differences in cellular uptake and NLRP3 inflammasome activation, which depends on the propensity toward lysosomal damage and cathepsin B release in macrophages. Moreover, the in vitro hazard ranking was validated by the pro-fibrogenic potential of the tubes in vivo. Compared to pristine MWCNTs, strong cationic PEI-MWCNTs induced significant lung fibrosis, while carboxylation significantly decreased the extent of pulmonary fibrosis. These results demonstrate that surface charge plays an important role in the structure-activity relationships that determine the pro-fibrogenic potential of f-CNTs in the lung.

SU-D-211-04: Sector Intensity Modulated (SIM) Gamma Knife Stereotactic Radiosurgery

PURPOSE

The latest Gamma Knife (GK) system, Perfexion, consists of 192 Co-60 sources divided into eight sectors. Treatment delivery includes multiple shots placed at different positions. For every shot, each sector can be either blocked or open with four different aperture sizes. However, the beam-on time is designed to be fixed. We proposed an innovative concept, Sector Intensity Modulated (SIM) Gamma Knife by dynamically varying the beam-on time for each individual sector to improve stereotactic radiosurgery planning quality.

METHODS

The anatomic structures and dose matrices from each sector for every shot were obtained from the GK workstation. The beam-on time for each sector was decomposed with various discrete levels and brute-force algorithm was used to get the optimal solution. The resulting SIM plan was then re-entered into the GK workstation. Six indices were used to benchmark the plan quality: Coverage, Conformality, Gradient, Maximum Dose(s) to critical structure(s), Volume receiving over 8 and 12 Gy. All the SIM plans in comparison with the original plans were further reviewed by an experienced oncologist.

RESULTS

The simulations were tested on various pituitary adenoma cases. Results consistently showed that SIM yielded better plans with all quantitative indices improved compared to original plan. It provides better conformality, quicker drop off of the isodose line outside the tumor, lower doses to the critical structures as optical- nerve/chiasm while maintaining at least 99% coverage of the tumor. Results were more favorable according to oncologist's view. In particular, up to 20% or 0.6 cc volume decrease in healthy tissue receiving 8 Gy was observed. This may translate into clinically observable reduction in acute/late toxicities.

CONCLUSIONS

Our preliminary results show that Sector Intensity Modulated Gamma Knife offers superior treatment plans compared to the originally delivered plans. Further works as adding dynamic shot location and dynamic shot shaping will be discussed.

A Two-Step Optimization Method for Improving Multiple Brain Lesion Treatments with Robotic Radiosurgery

Planning robotic radiosurgery treatments for multiple (n > 3) metastatic brain lesions is challenging due to the need of satisfying a large number of dose-volume constraints and the requirement of prescribing different dose levels to individual targets. In this study, we developed a sequential two-step optimization technique to improve the planning quality of such treatments. In contrast to the conventional approach of where all targets are simultaneously planned, we have developed a two-step optimization method. In this method, the first step was to create treatment plans for individual targets. In the second step, the 3D dose matrices associated with each plan were exported to Dicom-RT digital files and subsequently optimized. For the optimization, a singular-value-decomposition (SVD) algorithm was implemented to minimize the dose interferences among different targets. Finally, we compared the optimized treatment plans with the treatment plans created using the conventional method to determine the effectiveness of the new method. Large improvements in target dose distributions as well as normal brain sparing were found for the two-step optimization treatment plans as compared with the conventional treatment plans. The two-step optimization significantly lowered the volume of normal brain receiving relatively low doses. For example, the normal brain volume receiving 12-Gy was reduced by averaged 42% (range 34%–47%) with the two-step optimization. Such improvements generally enlarged with increasing number of targets being treated regardless of target sizes. Of note, normal brain dose was found to increase non-linearly with increasing number of targets. In summary, a two-step optimization technique is demonstrated to significantly improve the treatment plan quality as well as reduce the planning effort for multi-target robotic radiosurgery.

Phase I pharmacokinetic (PK) and pharmacodynamic (PD) study of LBH589, a novel deacetylase (DAC) inhibitor given intravenously on a new once weekly schedule

14019

Background: LBH589 is a novel deacetylase inhibitor that inhibits proliferation of tumor cells at nanomolar levels. This phase I study tested the safety and tolerability of IV LBH589 once each week for 3 of 4 wks in pts with advanced solid tumors or lymphoma. Methods: LBH589 was administered IV over 30 min. on days 1, 8 and 15 of a 28-day cycle. Western blots on peripheral blood lymphocytes were used to study histone acetylation (HA). Plasma PK profiles were analyzed on Days 1 and 8. Results: Thirty five pts (median age: 70 yrs; 23M, 12F) have been treated on 3 dose levels [10 mg/m2 (8pts), 15 mg/m2 (8 pts), 20 mg/m2 (19 pts)] with the following tumor types: Cutaneous and peripheral T cell lymphoma (7 pts), prostate (6 pts), mesothelioma (4 pts), colon (3 pts) and other (15 pts). There was one dose-limiting toxicity (transient grade 4 thrombocytopenia) at 20 mg/m2, none at the lower doses. Other G3/G4 toxicities (all cycles) include: transient thrombocytopenia (G4–5 pts, G3–5 pts), neutropenia (G3–2 pts), anemia (G3–5 pts), G3 hypophosphatemia (1 pt), G3 hypokalemia (1 pt), G3 nausea (1 pt) and G3 pruritus (1 pt). Thrombocytopenia was transient. Of 2,042 ECGs, 1 pt had an increase in QTcF from baseline of > 60 msec another with a QTcF >500 msec, both at 20 mg/m2. There was a dose-dependent increase in HA 7 days after one dose with 43% (10 mg/m2), 50% (15 mg/m2) and 60% (20 mg/m2) of pts with increased acetylation. The LBH589 plasma conc. peaked at the end of the 0.5 hr infusion with a mean terminal half-life of 16 hr. Median Cmax achieved with 20 mg/m2 was 1,000 ng/mL (2.86 μM). The AUC0-inf increased linearly with IV doses of 10–20 mg/m2. One pt with CTCL achieved a complete response (CR) on cycle 3, Day 1; this pt had previously received oral LBH589 at 20 mg MWF, achieving a CR on cycle 6, Day 28 that lasted for 7 months. One peripheral T-Cell lymphoma pt achieved a partial response that has persisted for >7 months. One pt with prostate cancer has had a 26% reduction in nodal disease and > 50% drop in PSA in the first 2 cycles. Conclusions: The maximum tolerated dose of LBH589 given IV wkly on a 3 of 4 wk schedule is 20 mg/m2. This dose produced sustained PD effects and higher systemic exposure compared to oral LBH589. Preliminary evidence of antitumor activity has been observed.

No significant financial relationships to disclose.

Cell cycle-dependent usage of transcriptional start sites. A novel mechanism for regulation of cyclin B1

Cyclin B1 mRNA is expressed temporally throughout the cell cycle with peak expression in G2 and M phase. Both transcriptional and posttranscriptional controls are important for this cell cycle-dependent regulation of cyclin B1 mRNA. In this study, we observed that cyclin B1 has two major transcripts: (a) a constitutively expressed transcript, and (b) a cell cycle-regulated transcript expressed predominantly during G2-M phase. These different transcripts are due to alternative start sites. The constitutively expressed transcript starts 65 bases upstream from the cell cycle-regulated message. Changes in mRNA stability did not appear to control the expression of the cell cycle-specific transcript, but we were able to identify a 24-base pair region of the cyclin B1 promoter spanning the start site of the cell cycle-regulated transcript that was critical for its cell cycle-regulated promoter activity. This suggests that transcriptional regulation is responsible for controlling the presence of each message. The 24-base pair sequence required for cell cycle regulation was notable for containing the nucleotides GGCT repeated three times. The possibility that these two transcripts might be physiologically distinct was raised when the cell cycle-specific transcript was found to be translated more efficiently in vitro than the constitutively expressed transcript. These results characterize a novel mechanism for the regulation of cyclin B1 throughout the cell cycle that is dependent upon the use of different transcriptional start sites.

Radiation and the G2 phase of the cell cycle

Exposure of mammalian cells to X rays results in prolongation of the cell cycle, including delays or arrests in G1, S and G2 phase. While G1-phase arrest occurs only in cells with wild-type p53 function, a G2-phase delay occurs in all cells regardless of p53 status. In this review, we summarize what is known about cell cycle progression through G2 and M phase and discuss the experimental findings that implicate different mechanisms in the G2-phase delay. Finally, we consider the possibility that G2-phase arrest plays a role in cell survival after irradiation.

Delayed cyclin B1 expression during the G2 arrest following DNA damage

Exposure of cells to DNA damaging agents results in a G2 arrest. Exposure of HeLa cells to camptothecin, etoposide or nitrogen mustard for 1 h in S phase resulted in delayed expression of cyclin B1 mRNA during the G2 arrest. Initially the levels of cyclin B1 protein were low as well; however, with extended time the cells blocked in G2 regained higher levels of cyclin B1 protein. In the case of cells treated with nitrogen mustard the higher levels coincided with cells exiting the G2 block into G1. However, with camptothecin or etoposide treatment, while the accumulation of cyclin B1 protein was delayed, its levels eventually surpassed peak levels seen in control cells, in spite of the fact that cells were still blocked in G2. These cells did not continue to progress through the cell cycle indicating further complexity to the mechanisms underlying the G2 block. Decreased transcription and stability of cyclin B1 mRNA were shown to occur after treatment with these DNA damaging agents. These results indicate that suppression of cyclin B1 mRNA expression is one consequence of DNA damage in HeLa cells.