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Previous studies indicate that breast cancer cells with high aldehyde dehydrogenase (ALDH) activity and CD44 expression (ALDHhiCD44+) contribute to metastasis and therapy resistance, and that ALDH1 correlates with poor outcome in breast cancer patients. The current study hypothesized that ALDH1 functionally contributes to breast cancer metastatic behavior and therapy resistance. Expression of ALDH1A1 or ALDH1A3 was knocked down in MDA-MB-468 and SUM159 human breast cancer cells using siRNA. Resulting impacts on ALDH activity (Aldefluor® assay); metastatic behavior and therapy response in vitro (proliferation/adhesion/migration/colony formation/chemotherapy and radiation) and extravasation/metastasis in vivo (chick choroiallantoic membrane assay) was assessed. Knockdown of ALDH1A3 but not ALDH1A1 in breast cancer cells decreased ALDH activity, and knockdown of ALDH1A1 reduced breast cancer cell metastatic behavior and therapy resistance relative to control (p < 0.05). In contrast, knockdown of ALDH1A3 did not alter proliferation, extravasation, or therapy resistance, but increased adhesion/migration and decreased colony formation/metastasis relative to control (p < 0.05). This is the first study to systematically examine the function of ALDH1 isozymes in individual breast cancer cell behaviors that contribute to metastasis. Our novel results indicate that ALDH1 mediates breast cancer metastatic behavior and therapy resistance, and that different enzyme isoforms within the ALDH1 family differentially impact these cell behaviors.

The majority of breast cancer deaths are because of ineffective treatment of metastatic disease. We previously identified a subpopulation of cells in human breast cancer cell lines that demonstrate high activity of aldehyde dehydrogenase (ALDH) and high expression of CD44. These ALDH hi CD44 + cells displayed enhanced metastatic behavior in vitro and in vivo relative to ALDH low CD44 − cells. The goal of this study was to test the hypothesis that ALDH hi CD44 + breast cancer cells are more resistant to standard cancer therapy, and that inhibiting ALDH activity through all- trans retinoic acid (ATRA) or the specific ALDH inhibitor diethylaminobenzaldehyde (DEAB) sensitizes these cells to treatment. ALDH hi CD44 + and ALDH low CD44 − populations were isolated from MDA-MB-231 and MDA-MB-468 cells lines and exposed to chemotherapy (doxorubicin/paclitaxel) or radiotherapy ± ATRA or DEAB. Cell populations were assessed for differences in survival, colony formation, and protein expression related to therapy resistance and differentiation. Significantly more ALDH hi CD44 + cells survived chemotherapy/radiotherapy relative to ALDH low CD44 − cells ( P  < 0.001). Glutathione-S-transferase pi, p-glycoprotein, and/or CHK1 were overexpressed in ALDH hi CD44 + populations compared with ALDH low CD44 − populations ( P  < 0.05). Pre-treatment of cell populations with DEAB or ATRA had no effect on ALDH low CD44 − cells, but resulted in significant initial sensitization of ALDH hi CD44 + cells to chemotherapy/radiotherapy. However, only DEAB had a long-term effect, resulting in reduced colony formation ( P  < 0.01). ATRA also significantly increased expression of CK8/18/19 in MDA-MB-468 ALDH hi CD44 + cells compared with control ( P  < 0.05). Our novel findings indicate that ALDH hi CD44 + breast cancer cells contribute to both chemotherapy and radiation resistance and suggest a much broader role for ALDH in treatment response than previously reported.

Cancer stem cells (CSCs) have recently been identified in leukaemia and solid tumours; however, the role of CSCs in metastasis remains poorly understood. This dearth of knowledge about CSCs and metastasis is due largely to technical challenges associated with the use of primary human cancer cells in pre‐clinical models of metastasis. Therefore, the objective of this study was to develop suitable pre‐clinical model systems for studying stem‐like cells in breast cancer metastasis, and to test the hypothesis that stem‐like cells play a key role in metastatic behaviour. We assessed four different human breast cancer cell lines (MDA‐MB‐435, MDA‐MB‐231, MDA‐MB‐468, MCF‐7) for expression of prospective CSC markers CD44/CD24 and CD133, and for functional activity of aldehyde dehydrogenase (ALDH), an enzyme involved in stem cell self‐protection. We then used fluorescence‐activated cell sorting and functional assays to characterize differences in malignant/metastatic behaviour in vitro (proliferation, colony‐forming ability, adhesion, migration, invasion) and in vivo (tumorigenicity and metastasis). Sub‐populations of cells demonstrating stem‐cell‐like characteristics (high expression of CSC markers and/or high ALDH) were identified in all cell lines except MCF‐7. When isolated and compared to ALDHlowCD44low/– cells, ALDHhiCD44+CD24− (MDA‐MB‐231) and ALDHhiCD44+CD133+ (MDA‐MB‐468) cells demonstrated increased growth (P < 0.05), colony formation (P < 0.05), adhesion (P < 0.001), migration (P < 0.001) and invasion (P < 0.001). Furthermore, following tail vein or mammary fat pad injection of NOD/SCID/IL2γ receptor null mice, ALDHhiCD44+CD24− and ALDHhiCD44+CD133+ cells showed enhanced tumorigenicity and metastasis relative to ALDHlowCD44low/– cells (P < 0.05). These novel results suggest that stem‐like ALDHhiCD44+CD24− and ALDHhiCD44+CD133+ cells may be important mediators of breast cancer metastasis.

Patients and the wider public are beneficiaries of scientific research that leads to new drugs and medical technologies, but they can and should be able to contribute to these advances through participation in clinical studies, co-design of research and input into regulatory processes.Patients and the wider public are beneficiaries of scientific research that leads to new drugs and medical technologies, but they can and should be able to contribute to these advances through participation in clinical studies, co-design of research and input into regulatory processes.

Introduction The unique evidentiary, economic and ethical challenges associated with health technology assessment (HTA) of precision therapies limit access to novel drugs and therapeutics for children and youth, for whom such challenges are amplified. We elicited citizens' perspectives about values‐based criteria relevant to the assessment of paediatric precision therapies to inform the development of a child‐tailored HTA framework. Methods We held four citizen panels virtually in May–June 2021, informed by a plain‐language citizen brief summarizing global and local evidence about the challenges, policy and programmatic options and implementation strategies related to enhancing access to precision therapies for Canadian children and youth. Panellists were recruited through a nationally representative database, medical/patient networks and social media. We inductively coded and thematically analysed panel transcripts to generate themes and identify priority values. Results The perspectives of panellists (n = 45) coalesced into four overlapping themes, with attendant subthemes, relevant to a child‐tailored HTA framework: (1) Childhood Distinctions: vulnerability, ‘fair innings’, future potential, family impacts; (2) Voice: agency of children and youth; lived versus no lived experience; (3) One versus Many: disease severity, rarity, equity, unmet need and (4) Health System Governance: funding, implementation inequities, effectiveness and safety. Participants broadly agreed that childhood distinctions, particularly family impacts, justify child‐tailored HTA. Dissent arose over whose voice should inform HTA and how such perspectives are best incorporated. Conclusions Citizens can offer unique insights into criteria relevant to the development or revision of HTA frameworks to capture holistic, societally responsive dimensions of value attached to unique contexts or populations, including children. Balancing the hopes and expectations of patients and caregivers for access to expensive but potential life‐altering therapies against the opportunity costs borne by encompassing health systems is a fundamental challenge that will require rigorous methods to elicit, weigh and reconcile varied views. Patient or Public Contribution A patient advocate served on the steering committee of this study and co‐authored this article. Key informants for the Citizen Brief included patient advocates and caregivers; a separate patient advocate reviewed the Brief before dissemination. Qualitative and quantitative data were collected from the general public and caregivers of children, with written consent.

Conducting clinical trials (CTs) with children presents several challenges. A major challenge is the need to enrol participants at multiple sites across different jurisdictions. Regardless of whether the trials involve children, adults, or both, CTs need to meet separate Competent Authority (CA) requirements to proceed in each participating country. This work, undertaken by the Working Group (WG) on International Collaborations at the European Network of Pediatric Research at the European Medicines Agency (Enpr-EMA) aims to describe the regulatory requirements including any specific to pediatrics, as well as current or upcoming changes across six jurisdictions-the European Union (EU), United Kingdom (UK), United States of America (USA), Canada, Japan, and Australia. An open questionnaire developed by the WG and directed at both the CA and the national pediatric clinical trial networks arranged by jurisdictions. A synopsis of the current legislative and regulatory requirements for CTs applications, application submission processes and application requirements is presented for each of the six jurisdictions. Requirements were found to be mostly consistent across jurisdictions. No difference was found in processes for CTs submission, review, and authorization for pediatric CTs vs. CTs in adults. However, there are additional Ethics Committee/Institutional Review Board requirements for clinical trials including children. Some jurisdictions are considering adopting a risk-based approach, inspired by the Organization of Economic Co-operation and Development (OECD) recommendations on Governance. Changes currently or soon to be implemented in some jurisdictions are also described. Regulators from the jurisdictions represented in this WG are collaborating to facilitate regulatory harmonization and foster international alignment of pediatric CTs. By interacting with their respective regulatory bodies and developing expertise in their jurisdiction's regulatory requirements, national pediatric networks can support both academic and industry sponsors in navigating the regulatory process for CTs.

Conducting clinical drug trials (CTs) with children presents several challenges. A major challenge is the need to enroll participants at multiple sites across different jurisdictions. Recruiting the required number of children within a reasonable timeframe requires the study to be reviewed by Research Ethics Boards (REB) or Institutional Review Boards (IRB) at multiple sites across various jurisdictions. This work, undertaken by the Working Group (WG) on International Collaborations at the European Network of Pediatric Research at the European Medicines Agency (Enpr-EMA) aims to describe the research ethics review requirements including any pediatric specific requirements, as well as current or upcoming changes across six jurisdictions - the European Union (EU), United Kingdom (UK), United States of America (USA), Canada, Japan, and Australia. An open questionnaire developed by the WG and directed at both the Competent Authorities (CA) and the national pediatric clinical trial networks arranged by jurisdictions. A synopsis of the current regulatory requirements covers centralized versus independent review, comparisons between investigator initiated and industry sponsored clinical trials, timelines, review board members requirements and the consenting/assent process for clinical trial (CT) applications, application submission processes and application requirements for each of the six jurisdictions. It also describes changes currently or soon to be implemented in some jurisdictions. This environmental scan highlights the differences in ethics review for CTs in pediatric medicine development across six jurisdictions. While there is a growing trend for centralized ethics review, it is not universally permitted due to institutional, state/provincial, or national policies. Even where central review is allowed, local review may still be required for vulnerable populations like children. Harmonized and centralized ethics reviews offer advantages such as expert pediatric reviewers and efficient and consistent evaluations.

A major hurdle in pediatric formulation development is the lack of safety and toxicity data on some of the commonly used excipients. While the maximum oral safe dose for several kinds of excipients is known in the adult population, the doses in pediatric patients, including preterm neonates, are not established yet due to the lack of evidence-based data. This paper consists of four parts: (1) country-specific perspectives in different parts of the world (current state, challenges in excipients, and ongoing efforts) for ensuring the use of safe excipients, (2) comparing and contrasting the country-specific perspectives, (3) past and ongoing collaborative efforts, and (4) future perspectives on excipients for pediatric formulation. The regulatory process for pharmaceutical excipients has been developed. However, there are gaps between each region where a lack of information and an insufficient regulation process was found. Ongoing efforts include raising issues on excipient exposure, building a region-specific database, and improving excipient regulation; however, there is a lack of evidence-based information on safety for the pediatric population. More progress on clear safety limits, quantitative information on excipients of concern in the pediatric population, and international harmonization of excipients’ regulatory processes for the pediatric population are required.

The majority of breast cancer deaths are because of ineffective treatment of metastatic disease. We previously identified a subpopulation of cells in human breast cancer cell lines that demonstrate high activity of aldehyde dehydrogenase (ALDH) and high expression of CD44. These [ALDH.sup.hi][CD44.sup.+] cells displayed enhanced metastatic behavior in vitro and in vivo relative to [ALDH.sup.low][CD44.sup.-] cells. The goal of this study was to test the hypothesis that [ALDH.sup.hi][CD44.sup.+] breast cancer cells are more resistant to standard cancer therapy, and that inhibiting ALDH activity through all-trans retinoic acid (ATRA) or the specific ALDH inhibitor diethylaminobenzaldehyde (DEAB) sensitizes these cells to treatment. [ALDH.sup.hi][CD44.sup.+] and [ALDH.sup.low][CD44.sup.-] populations were isolated from MDA-MB-231 and MDA-MB-468 cells lines and exposed to chemotherapy (doxorubicin/paclitaxel) or radiotherapy ± ATRA or DEAB. Cell populations were assessed for differences in survival, colony formation, and protein expression related to therapy resistance and differentiation. Significantly more [ALDH.sup.hi][CD44.sup.+] cells survived chemotherapy/radiotherapy relative to [ALDH.sup.low][CD44.sup.-] cells (P < 0.001). Glutathione-Stransferase pi, p-glycoprotein, and/or CHK1 were overexpressed in [ALDH.sup.hi][CD44.sup.+] populations compared with [ALDH.sup.low][CD44.sup.-] populations (P < 0.05). Pre-treatment of cell populations with DEAB or ATRA had no effect on [ALDH.sup.low][CD44.sup.-] cells, but resulted in significant initial sensitization of [ALDH.sup.hi][CD44.sup.+] cells to chemotherapy/ radiotherapy. However, only DEAB had a long-term effect, resulting in reduced colony formation (P < 0.01). ATRA also significantly increased expression of CK8/18/19 in MDA-MB-468 [ALDH.sup.hi][CD44.sup.+] cells compared with control (P < 0.05). Our novel findings indicate that [ALDH.sup.hi][CD44.sup.+] breast cancer cells contribute to both chemotherapy and radiation resistance and suggest a much broader role for ALDH in treatment response than previously reported. Keywords Breast cancer * Stem-like cells * Aldehyde dehydrogenase * Therapy resistance * All-trans retinoic acid