TP53 mutation status and consensus molecular subtypes of colorectal cancer in patients from Rwanda.

BACKGROUND: Mutations in the TP53 tumor suppressor gene are well-established drivers of colorectal cancer (CRC) development. However, data on the prevalence of TP53 variants and their association with consensus molecular subtype (CMS) classification in patients with CRC from Rwanda are currently lacking. This study addressed this knowledge gap by investigating TP53 mutation status concerning CMS classification in a CRC cohort from Rwanda. METHODS: Formalin-fixed paraffin-embedded (FFPE) tissue blocks were obtained from 51 patients with CRC at the University Teaching Hospital of Kigali, Rwanda. Exons 4 to 11 and their flanking intron-exon boundaries in the TP53 gene were sequenced using Sanger sequencing to identify potential variants. The recently established immunohistochemistry-based classifier was employed to determine the CMS of each tumor. RESULTS: Sequencing analysis of cancerous tissue DNA revealed TP53 pathogenic variants in 23 of 51 (45.1%) patients from Rwanda. These variants were predominantly missense types (18/23, 78.3%). The most frequent were c.455dup (p.P153Afs*28), c.524G > A (p.R175H), and c.733G > A (p.G245S), each identified in three tumors. Trinucleotide sequence context analysis of the 23 mutations (20 of which were single-base substitutions) revealed a predominance of the [C > N] pattern among single-base substitutions (SBSs) (18/20; 90.0%), with C[C > T]G being the most frequent mutation (5/18, 27.8%). Furthermore, pyrimidine bases (C and T) were preferentially found at the 5' flanking position of the mutated cytosine (13/18; 72.2%). Analysis of CMS subtypes revealed the following distribution: CMS1 (microsatellite instability-immune) (6/51, 11.8%), CMS2 (canonical) (28/51, 54.9%), CMS3 (metabolic) (9/51, 17.6%), and CMS4 (mesenchymal) (8/51, 15.7%). Interestingly, the majority of TP53 variants were in the CMS2 subgroup (14/23; 60.1%). CONCLUSION: Our findings indicate a high frequency of TP53 variants in CRC patients from Rwanda. Importantly, these variants are enriched in the CMS2 subtype. This study, representing the second investigation into molecular alterations in patients with CRC from Rwanda and the first to explore TP53 mutations and CMS classification, provides valuable insights into the molecular landscape of CRC in this understudied population.

The spectrum of TP53 mutations in Rwandan patients with gastric cancer.

BACKGROUND: Gastric cancer is the sixth most frequently diagnosed cancer and third in causing cancer-related death globally. The most frequently mutated gene in human cancers is TP53, which plays a pivotal role in cancer initiation and progression. In Africa, particularly in Rwanda, data on TP53 mutations are lacking. Therefore, this study intended to obtain TP53 mutation status in Rwandan patients with gastric cancer. RESULTS: Formalin-fixed paraffin-embedded tissue blocks of 95 Rwandan patients with histopathologically proven gastric carcinoma were obtained from the University Teaching Hospital of Kigali. After DNA extraction, all coding regions of the TP53 gene and the exon-intron boundary region of TP53 were sequenced using the Sanger sequencing. Mutated TP53 were observed in 24 (25.3%) of the 95 cases, and a total of 29 mutations were identified. These TP53 mutations were distributed between exon 4 and 8 and most of them were missense mutations (19/29; 65.5%). Immunohistochemical analysis for TP53 revealed that most of the TP53 missense mutations were associated with TP53 protein accumulation. Among the 29 mutations, one was novel (c.459_477delCGGCACCCGCGTCCGCGCC). This 19-bp deletion mutation in exon 5 caused the production of truncated TP53 protein (p.G154Wfs*10). Regarding the spectrum of TP53 mutations, G:C > A:T at CpG sites was the most prevalent (10/29; 34.5%) and G:C > T:A was the second most prevalent (7/29; 24.1%). Interestingly, when the mutation spectrum of TP53 was compared to three previous TP53 mutational studies on non-Rwandan patients with gastric cancer, G:C > T:A mutations were significantly more frequent in this study than in our previous study (p = 0.013), the TCGA database (p = 0.017), and a previous study on patients from Hong Kong (p = 0.006). Even after correcting for false discovery, statistical significance was observed. CONCLUSIONS: Our results suggested that TP53 G:C > T:A transversion mutation in Rwandan patients with gastric cancer is more frequent than in non-Rwandan patients with gastric cancer, indicating at an alternative etiological and carcinogenic progression of gastric cancer in Rwanda.

Clinicopathological Characteristics and Mutational Landscape of APC, HOXB13, and KRAS among Rwandan Patients with Colorectal Cancer.

Cancer research in Rwanda is estimated to be less than 1% of the total African cancer research output with limited research on colorectal cancer (CRC). Rwandan patients with CRC are young, with more females being affected than males, and most patients present with advanced disease. Considering the paucity of oncological genetic studies in this population, we investigated the mutational status of CRC tissues, focusing on the Adenomatous polyposis coli (APC), Kirsten rat sarcoma (KRAS), and Homeobox B13 (HOXB13) genes. Our aim was to determine whether there were any differences between Rwandan patients and other populations. To do so, we performed Sanger sequencing of the DNA extracted from formalin-fixed paraffin-embedded adenocarcinoma samples from 54 patients (mean age: 60 years). Most tumors were located in the rectum (83.3%), and 92.6% of the tumors were low-grade. Most patients (70.4%) reported never smoking, and 61.1% of patients had consumed alcohol. We identified 27 variants of APC, including 3 novel mutations (c.4310_4319delAAACACCTCC, c.4463_4470delinsA, and c.4506_4507delT). All three novel mutations are classified as deleterious by MutationTaster2021. We found four synonymous variants (c.330C>A, c.366C>T, c.513T>C, and c.735G>A) of HOXB13. For KRAS, we found six variants (Asp173, Gly13Asp, Gly12Ala, Gly12Asp, Gly12Val, and Gln61His), the last four of which are pathogenic. In conclusion, here we contribute new genetic variation data and provide clinicopathological information pertinent to CRC in Rwanda.

Exploring Perceptions and Acceptance of Minimally Invasive Tissue Sampling among Bereaved Relatives and Health-Care Professionals in Rwanda.

PURPOSE: In most low- and lower middle-income countries (LMICs), minimally invasive tissue sampling (MITS) is a relatively new procedure for identifying the cause of death (CoD). This study aimed to explore perceptions and acceptance of bereaved families and health-care professionals regarding MITS in the context of MITS initiation in Rwanda as an alternative to clinical autopsy. METHODS: This was a qualitative phenomenological study with thematic analysis. Participants were bereaved relatives (individual interviews) and health-care professionals (focus-group discussions) involved in MITS implementation. It was conducted in the largest referral and teaching hospital in Rwanda. RESULTS: Motivators of MITS acceptance included eagerness to know the CoD, noninvasiveness of MITS, trust in medics, and the fact that it was free. Barriers to consent to MITS included inadequate explanations from health-care professionals, high socioeconomic status, lack of power to make decisions, and lack of trust in medics. Health-care professionals perceived both conventional autopsy and MITS as gold-standard procedures in CoD determination. They recommended including MITS among hospital services and commended the post-MITS multidisciplinary discussion panel in CoD determination. They pointed out that there might be reticence in approaching bereaved relatives to obtain consent for MITS. Both groups of participants highlighted the issue of delay in releasing MITS results. CONCLUSION: Both health-care professionals and bereaved relatives appreciate that MITS is an acceptable procedure to include in routine hospital services. Dealing with barriers met by either group is to be considered in the eventual next phases of MITS implementation in Rwanda and similar sociocultural contexts.

Building Capacity and Infrastructure at Hospitals Implementing Minimally Invasive Tissue Sampling: Experience and Lessons Learned From Nepal, Rwanda, and Tanzania.

BACKGROUND: Minimally invasive tissue sampling (MITS) is a useful tool to determine cause of death in low- and middle-income countries (LMICs). In 2019 the MITS Surveillance Alliance supported the implementation of small-scale postmortem studies using MITS in several LMICs. METHODS: In this article we describe the preparations, challenges, and lessons learned as part of implementing MITS across 4 study sites in 3 countries: Nepal, Rwanda, and Tanzania. We describe the process for building capacity to conduct MITS, which consisted of training in MITS sample collection, individual site assessment to determine readiness and gaps prior to implementation, site visits as sites began implementation of MITS, and feedback based on remote evaluation of histology slides via an online portal. RESULTS: The 4 study sites each conducted 100 MITS, for a total of 400. All 4 sites lacked sufficient infrastructure and facilities to conduct MITS, and upgrades were required. Common challenges faced by sites included that clinical autopsies were neither routinely conducted nor widely accepted. Limited clinical records made cause of death determination more difficult. Lessons learned included the importance of sensitization of the community and medical staff to MITS to enhance understanding and increase consent. CONCLUSIONS: The study sites accomplished MITS and utilized the available support systems to overcome the challenges. The quality of the procedures was satisfactory and was facilitated through the organized capacity-building programs.

Cost Evaluation of Minimally Invasive Tissue Sampling (MITS) Implementation in Low- and Middle-Income Countries.

BACKGROUND: Low- and middle-income countries (LMICs) face disproportionately high mortality rates, yet the causes of death in LMICs are not robustly understood, limiting the effectiveness of interventions to reduce mortality. Minimally invasive tissue sampling (MITS) is a standardized postmortem examination method that holds promise for use in LMICs, where other approaches for determining cause of death are too costly or unacceptable. This study documents the costs associated with implementing the MITS procedure in LMICs from the healthcare provider perspective and aims to inform resource allocation decisions by public health decisionmakers. METHODS: We surveyed 4 sites in LMICs across Sub-Saharan Africa and South Asia with experience conducting MITS. Using a bottom-up costing approach, we collected direct costs of resources (labor and materials) to conduct MITS and the pre-implementation costs required to initiate MITS. RESULTS: Initial investments range widely yet represent a substantial cost to implement MITS and are determined by the existing infrastructure and needs of a site. The costs to conduct a single case range between $609 and $1028 per case and are driven by labor, sample testing, and MITS supplies costs. CONCLUSIONS: Variation in each site's use of staff roles and testing protocols suggests sites conducting MITS may adapt use of resources based on available expertise, equipment, and surveillance objectives. This study is a first step toward necessary examinations of cost-effectiveness, which may provide insight into cost optimization and economic justification for the expansion of MITS.