Cancer prevention in Africa: liver cancer

Knockdown of METTL5 inhibits the Myc pathway to downregulate PD-L1 expression and inhibits immune escape of hepatocellular carcinoma cells

The incidence of hepatocellular carcinoma (HCC) is raised annually, which causes a great harm to people's health. This research aimed to investigate the influence and mechanism of methyltransferase-like 5 (METTL5) in HCC. According to The Cancer Genome Atlas (TCGA) database, METTL5 levels and prognosis was analyzed in HCC. Next, in HCC tissues and cells, METTL5 expression was examined via quantitative real-time polymerase chain reaction (qRT-PCR). Biological behaviors of HCC cells were assessed by Cell Counting Kit-8 (CCK-8), colony formation, transwell and flow cytometry assays. Gene Set Enrichment Analysis (GSEA) was applied to predict METTL5 related pathway. The possible binding sites of programmed cell death 1 ligand 1 (PD-L1) and myelocytomatosis viral oncogene (Myc) was predicted by JASPAR database. Western blot was utilized to test the change of PD-L1 and Myc pathway related proteins [cellular (c)-Myc, chaperonin containing TCP1 subunit 2 (CCT2) and chromobox protein homolog 3 (CBX3)]. In HCC tissues and cells, METTL5 expression was increased. High METTL5 expression was associated with poor prognosis. Knockdown of METTL5 inhibited HCC cell proliferation and invasion, induced cell apoptosis and reduced the expression of PD-L1, c-Myc, CCT2 and CBX3. The bind between PD-L1 and the Myc promoter in HCC cells was confirmed using Chip and luciferase reporter assays. Moreover, the influences of knockdown of METTL5 on PD-L1 expression and HCC cell biological behaviors were reversed by overexpression of Myc. Knockdown of METTL5 inhibited PD-L1 expression and malignant cell behavior of HCC through inhibiting the Myc pathway.

Aflatoxin Contamination of Maize, Groundnut, and Sorghum Grown in Burkina Faso, Mali, and Niger and Aflatoxin Exposure Assessment

Aflatoxin contamination of staple crops by Aspergillus flavus and closely related fungi is common across the Sahel region of Africa. Aflatoxins in maize, groundnut, and sorghum collected at harvest or from farmers' stores within two weeks of harvest from Burkina Faso, Mali, and Niger were quantified. Thereafter, aflatoxin exposure values were assessed using per capita consumption rates of those crops. Mean aflatoxin concentrations in maize were high, 128, 517, and 659 µg/kg in Mali, Burkina Faso, and Niger, respectively. The estimated probable daily intake (PDI) of aflatoxins from maize ranged from 6 to 69, 29 to 432, and 310 to 2100 ng/kg bw/day in Mali, Burkina Faso, and Niger, respectively. Similarly, mean aflatoxin concentrations in sorghum were high, 76 and 259 µg/kg in Mali and Niger, respectively, with an estimated PDI of 2-133 and 706-2221. For groundnut, mean aflatoxin concentrations were 115, 277, and 628 µg/kg in Mali, Burkina Faso, and Niger, respectively. Aflatoxin exposure values were high with an estimated 9, 28, and 126 liver cancer cases/100,000 persons/year in Mali, Burkina Faso, and Niger, respectively. Several samples were extremely unsafe, exceeding manyfold regulatory levels of diverse countries (up to 2000 times more). Urgent attention is needed across the Sahel for integrated aflatoxin management for public health protection, food and nutrition security, and access to trade opportunities.

Viral hepatitis associated hepatocellular carcinoma on the African continent, the past, present, and future: a systematic review

Background

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths in Africa. In Africa, the major causes of HCC include chronic infection with hepatitis B virus (HBV) and/or hepatitis C virus (HCV). Knowledge of the changes in the incidence of viral hepatitis-associated HCC over time and the factors responsible for such changes is key in informing policies for the prevention of viral hepatitis-associated HCC in Africa.

Aim

The study aimed to systematically summarize the changes in the prevalence of viral hepatitis among HCC patients and the overall effect of the prevalence of viral hepatitis on the incidence of HCC over the past four decades in Africa (1980–2019).

Methods

A literature search was conducted in MEDLINE (PubMed), Google Scholar, Science Direct, Scopus, Web of Science, and African wide web for articles published on viral hepatitis-associated HCC in Africa from 1980 to 2019. The abstracts of the articles were screened for eligibility and those meeting the inclusion criteria were retrieved and reviewed.

Results

A total of 272 studies were included in the analysis. Viral hepatitis-related HCC incidence changed by 1.17% (95% confidence interval (CI): 0.63–1.71, p < 0.001), 0.82% (95% CI: 0.45–1.18, p < 0.001), and 3.34% (95% CI: 2.44–4.25, p < 0.001) for every 1% change in the prevalence of HBV, HCV, and hepatitis D virus (HDV) respectively, per decade. The incidence of HBV-related HCC decreased by − 0.50% (95% CI: − 0.74 – − 0.25, p < 0.001) over the last 40 years, while HCV-related HCC increased.

Conclusion

Overall, the incidence of viral hepatitis-associated HCC has not declined, mainly due to no decline in the prevalence of HCV, HDV, and the high number of chronic hepatitis B carriers on the African continent. There is an urgent need for the allocation of resources for the implementation of treatment and preventive programs for HBV, HCV, HDV, and HCC in Africa.

This systematic review is registered with PROSPERO®, number CRD42020169723.

MiR-155 Inhibits Malignant Biological Behavior of Human Liver Cancer Cells by Regulating SRPK1

Although the treatment of liver cancer has made great progress, the mechanism of its occurrence is not completely clear. miR-155 plays an important regulatory role in tumorigenesis and development, including survival, proliferation, migration and invasion. However, the role and regulatory mechanism of miR-155 in liver cancer has rarely been reported. We analyzed miR-155 expression in liver cancer tissue samples and cell lines by qRT-PCR. The expression of miR-155 was measured by qRT-PCR before and after miR-155-mimic and sh-miR-155 transfection. CCK-8 and clonogenic assays were used to detect the proliferation of liver cancer cells. Cell scratch and invasion assays were used to detect migration and invasion. RNA-seq was used to detect the difference in RNA expression in liver cancer cells. SRPK1 expression was detected in liver cancer cells before and after transfection by qRT-PCR and western blotting. We observed that miR-155 was downregulated in liver cancer tissues compared with normal tissues. Furthermore, we demonstrated that liver cancer cell proliferation, migration and invasion are markedly suppressed by miR-155. Importantly, we also demonstrated that SRPK1 is directly regulated by miR-155 during the process of liver cancer cell proliferation and metastasis. Finally, the overexpression of miR-155 inhibits malignant biological behavior of human liver cancer cells. We report the abnormal expression of the miR-155 cluster in liver cancer cells, which inhibits cancer cell proliferation and metastasis. In addition, we identified SRPK1 as a target gene of miR-155 during the process of liver cancer cell proliferation and metastasis.