US-born Latinas at great risk of having babies with retinoblastoma

In a large epidemiologic study, researchers at UCLA's Jonsson Cancer Center found that the children of U.S.-born Latina women are at higher risk of having retinoblastoma, a malignant tumor of the retina which typically occurs in children under six.

The study, which focused on babies born in California, also found that offspring of older fathers were at greater risk for retinoblastoma, as were children born to women with sexually transmitted diseases and those born in multiple births, which may indicate an increased risk from in vitro fertilization. Those findings confirmed the results of several smaller studies.

The research team used data from the California Cancer Registry and examined all retinoblastoma cases reported from 1988 to 2007, said Julia Heck, the study's first author and an assistant researcher in the UCLA Fielding School of Public Health. Using California data allowed the researchers to cull information from a large and diverse population that included many Latinas.

The study appears in the early online edition of the journal Cancer Causes & Control.

"One of the most interesting things we found in this study that hasn't been reported is the differences among Latina mothers and the risk being lower among mothers born in Mexico," Heck said. "We believe this is because women born in Mexico who come to the United States and have children have very healthy behaviors in the perinatal period, immediately before and after giving birth."

Study senior author Dr. Beate Ritz, a Jonsson Cancer Center researcher and professor and chair of epidemiology and professor of environmental health sciences in the Fielding School, said Latinas born in the U.S. are less likely to exhibit the healthy pregnancy behaviors found in foreign-born Latinas. For example, they have poorer diets and are more likely to smoke and drink during pregnancy, which could contribute to the risks of retinoblastoma.

Do we know what causes retinoblastoma? Retinoblastoma is caused by mutations (changes) in certain genes. Over the past few decades, scientists have made great progress in understanding how certain changes in a person's DNA can cause cells of the retina to become cancerous. DNA is the chemical in each of our cells that makes up our genes – the instructions for how our cells function. We usually look like our parents because they are the source of our DNA. But DNA affects much more than the way we look.

Some genes have instructions that control when our cells grow, divide, and die. Certain genes that speed up cell division are called oncogenes. Others that slow down cell division, or cause cells to die at the right time, are called tumor suppressor genes. Cancers can be caused by DNA changes that turn on oncogenes or turn off tumor suppressor genes.

The most important gene involved in retinoblastoma is the RB1 tumor suppressor gene. This gene makes a protein (pRb) that helps stop cells from growing too quickly. Each cell normally has 2 RB1 genes. As long as a retinal cell has at least one RB1 gene that works as it should, it will not form a retinoblastoma. But when both of the RB1 genes are mutated or missing, a cell can grow unchecked. This can lead to further gene changes, which in turn may cause cells to become cancerous.