Building pathology capacity in sub-Saharan Africa to improve breast cancer diagnosis and treatment: training laboratory technicians in high-quality manual immunohistochemistry.

BACKGROUND: To address the need for a skilled workforce in breast cancer (BC) pathology in sub-Saharan Africa (SSA), we implemented an education program to train laboratory technicians in manual immunohistochemistry (IHC). METHODS: A quality improvement education project was developed. Interactive webinars were held every six months with didactics and presentations from African experts with experience in IHC. We conducted knowledge assessments and surveys on current practice, equipment, and human resources. A digital mentorship platform (DMP) was created for discussions, sharing SOPs, and networking. For one year (2022-2023), we followed developments in pathology capacity, practice changes, and educational needs. A paired t-test was used to calculate the significance of changes in knowledge immediately after the webinar and comfort level with topics 35 days after the webinar. RESULTS: Two hundred and sixty six participants from 10 SSA countries attended the first webinar, a series of six lectures on IHC theory, methods, and practice. Ninety-five participants from nine SSA countries provided a baseline assessment of pathology capacity and feedback. Mean knowledge increased by 17.4% immediately after the webinar (from 41.8% pre-webinar to 59.2% post, p = < 0.0001). Self-reported comfort level in topics 35 days after the webinar increased by 11.3%, but this was not statistically significant (mean 3.36 pre- to 3.74 post, p = 0.1). Over six months, recordings were accessed 412 times. After six months, the second webinar had 93 participants from eight SSA countries. Membership in the DMP increased from 64 to 172; recordings were viewed 412 times in six months; and 113 participants from nine SSA countries completed surveys. Among 74 respondents who perform IHC, 43.5% reported moderate or significant positive practice changes such as improved antigen retrieval techniques and optimization of preanalytical variables. Over half (52.7%, n = 39) reported the quality of slides had moderately or significantly improved. After one year, a third webinar had 98 participants from eight SSA countries. Thirty-eight completed surveys, DMP membership increased to 199, and 1 reported launching IHC in a lab in Nigeria. CONCLUSIONS: Our program 1) reached hundreds of participants and provided a baseline assessment of pathology capacity across nine SSA countries; 2) created a novel mechanism to build pathology capacity and assess progress with this cohort; and 3) improved practices and the preparation of slides for over half performing manual IHC. After one year, interest was sustained. Tracking impact on diagnosis and treatment of BC in the region is needed long-term.

The BMP2/4 ortholog Dpp can function as an inter-organ signal that regulates developmental timing.

Developmental transitions are often triggered by a neuroendocrine axis and can be contingent upon multiple organs achieving sufficient growth and maturation. How the neurodendocrine axis senses the size and maturity of peripheral organs is not known. In Drosophila larvae, metamorphosis is triggered by a sharp increase in the level of the steroid hormone ecdysone, secreted by the prothoracic gland (PG). Here, we show that the BMP2/4 ortholog Dpp can function as a systemic signal to regulate developmental timing. Dpp from peripheral tissues, mostly imaginal discs, can reach the PG and inhibit ecdysone biosynthesis. As the discs grow, reduced Dpp signaling in the PG is observed, consistent with the possibility that Dpp functions in a checkpoint mechanism that prevents metamorphosis when growth is insufficient. Indeed, upon starvation early in the third larval instar, reducing Dpp signaling in the PG abrogates the critical-weight checkpoint which normally prevents pupariation under these conditions. We suggest that increased local trapping of morphogen within tissues as they grow would reduce circulating levels and hence provide a systemic readout of their growth status.

Localized epigenetic silencing of a damage-activated WNT enhancer limits regeneration in mature Drosophila imaginal discs.

Many organisms lose the capacity to regenerate damaged tissues as they mature. Damaged Drosophila imaginal discs regenerate efficiently early in the third larval instar (L3) but progressively lose this ability. This correlates with reduced damage-responsive expression of multiple genes, including the WNT genes wingless (wg) and Wnt6. We demonstrate that damage-responsive expression of both genes requires a bipartite enhancer whose activity declines during L3. Within this enhancer, a damage-responsive module stays active throughout L3, while an adjacent silencing element nucleates increasing levels of epigenetic silencing restricted to this enhancer. Cas9-mediated deletion of the silencing element alleviates WNT repression, but is, in itself, insufficient to promote regeneration. However, directing Myc expression to the blastema overcomes repression of multiple genes, including wg, and restores cellular responses necessary for regeneration. Localized epigenetic silencing of damage-responsive enhancers can therefore restrict regenerative capacity in maturing organisms without compromising gene functions regulated by developmental signals.

TIE-DYE: a combinatorial marking system to visualize and genetically manipulate clones during development in Drosophila melanogaster.

Two types of information are particularly valuable in understanding the development of a tissue or an organ from a small population of founder cells. First, it is useful to know the composition of the final structure in terms the contribution of individual founder cells. Second, it is important to understand cell-cell interactions. To facilitate the study of both of these aspects of organ development at a tissue-wide level, we have developed a method, TIE-DYE, that allows simultaneous lineage tracing of multiple cell populations as well as the genetic manipulation of a subset of these populations. Seven uniquely marked categories of cells are produced by site-directed recombination of three independent cassettes. We have used the TIE-DYE method to estimate the number of founder cells that give rise to the wing-imaginal disc during normal development and following compensatory growth caused by X-ray irradiation of the founder cells. We also show that four out of the seven types of marked clones can be genetically manipulated by gene overexpression or RNAi knockdown, allowing an assessment of the consequences of these manipulations on the entire wing disc. We demonstrate the utility of this system in studying the consequences of alterations in growth, patterning and cell-cell affinity.

Specification of hepatopancreas progenitors in zebrafish by hnf1ba and wnt2bb.

Although the liver and ventral pancreas are thought to arise from a common multipotent progenitor pool, it is unclear whether these progenitors of the hepatopancreas system are specified by a common genetic mechanism. Efforts to determine the role of Hnf1b and Wnt signaling in this crucial process have been confounded by a combination of factors, including a narrow time frame for hepatopancreas specification, functional redundancy among Wnt ligands, and pleiotropic defects caused by either severe loss of Wnt signaling or Hnf1b function. Using a novel hypomorphic hnf1ba zebrafish mutant that exhibits pancreas hypoplasia, as observed in HNF1B monogenic diabetes, we show that hnf1ba plays essential roles in regulating ß-cell number and pancreas specification, distinct from its function in regulating pancreas size and liver specification, respectively. By combining Hnf1ba partial loss of function with conditional loss of Wnt signaling, we uncover a crucial developmental window when these pathways synergize to specify the entire ventrally derived hepatopancreas progenitor population. Furthermore, our in vivo genetic studies demonstrate that hnf1ba generates a permissive domain for Wnt signaling activity in the foregut endoderm. Collectively, our findings provide a new model for HNF1B function, yield insight into pancreas and ß-cell development, and suggest a new mechanism for hepatopancreatic specification.

Regeneration and transdetermination in Drosophila imaginal discs.

The study of regeneration in Drosophila imaginal discs provides an opportunity to use powerful genetic tools to address fundamental problems pertaining to tissue regeneration and cell plasticity. We present a historical overview of the field and describe how the application of modern methods has made the study of disc regeneration amenable to genetic analysis. Discs respond to tissue damage in several ways: (a) Removal of part of the disc elicits localized cell proliferation and regeneration of the missing tissue. (b) Damage at specific locations in the disc can cause cells to generate disc-inappropriate structures (e.g., wing instead of leg), a phenomenon known as transdetermination. (c) Diffuse damage to imaginal discs, results in compensatory proliferation of surviving cells. Candidate-gene approaches have implicated the JNK, Wingless, and Hippo pathways in regeneration. Recently developed systems will enable extensive genetic screens that could provide new insights into tissue regeneration, transdetermination and compensatory proliferation.