When and how much a parent smokes can have a significant impact on the chances of their children developing Acute Lymphoblastic Leukaemia (ALL), according to new research. The study, published in Cancer Research, investigated the connections between leukaemia-linked genetic deletions in children and their prenatal or early life exposure to tobacco smoke.

ALL is a very rare form of cancer, which affects both adults and children. Despite its rarity, ALL is the most common type of childhood leukaemia, with roughly 85% of cases in children affecting people younger than fifteen years old. Previous research has shown that ALL is caused by genetic mutations that impact the production of healthy white blood cells in the patient’s bone marrow, but the root cause of these mutations is still poorly understood.

This new study hoped to shed light on how parental smoking habits could impact the occurrence of leukaemia-related mutations across 8 somatic genes in their offspring. They also examined DNA methylation in the aryl-hydrocarbon receptor repressor (AHRR), which acts as an epigenetic biomarker of exposure to maternal smoking during pregnancy. To examine the genetic mutations, the team used 559 pre-treatment tumour samples from the California Childhood Leukaemia Study, and assessed smoking habits through interview-assisted questionnaires.

The team found that the number of leukaemia-linked mutations increased for all maternal smoking categories (ever smoked, smoking while pregnant, and smoking while breastfeeding), although the risk factors differed between the groups. Smoking five cigarettes a day while breastfeeding, for example, increased the number of deletions by 74%, however the strongest association was found in cases where the mother had smoked during pregnancy. Gender of the child was also a factor; the magnitude of maternal ever smoking association was shown to be stronger for male offspring than females.

The number of deletions was also found to correlate to DNA methylation of the AHRR epigenetic biomarker.

This research helps us understand more about what factors can influence a person’s risk of developing ALL and might influence future medical advice. The authors of the paper have specified that their research is limited by what the parents could recall about their smoking habits during the questionnaires, but the results are still a good starting point for future work.