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In laboratory studies of very early-stage breast cancers, researchers at the Johns Hopkins Kimmel Cancer Center found that injecting a targeted immunotoxin into the breast ducts through nipple openings wiped out all visible and invisible precancerous lesions.
A description of the work done on mice, which the authors say provides a strong pre-clinical foundation for conducting feasibility and safety trials with patients with stage 0 breast cancer, is published in the Proceedings of the National Academy of Sciences on June 8.
Stage 0 breast cancer, also known as ductal carcinoma in situ (DCIS), is characterized as the presence of abnormal, precancerous cells inside milk ducts in the breast, and it affects about 69,000 women each year in the United States. Many women have breast removal surgery and radiation treatments for these very early cancers, and in some cases, they receive chemotherapy or hormone therapies, says senior study author Saraswati Sukumar, Ph.D., a Johns Hopkins professor of oncology and pathology.
"In our research, we proposed an alternative treatment in which injecting the immunotoxin drug through the duct could result in cleaning out the DCIS," says Sukumar. "To our big surprise, the drugs killed every single lesion present in that breast duct. I had never seen such dramatic results in my life."
The researchers first tested the cell-killing effects of HB21(Fv)-PE40, a targeted immunotoxin, in four cell lines from different molecular subtypes of breast cancer. The toxin is made up of HB21, which is a monoclonal antibody (a protein that can bind to a specific target) (in this case, to the human transferrin receptor, a carrier protein found in breast cancers).
HB21 is fused to PE40, a bacterial toxin fragment that inhibits protein production in cells and causes cell death. The treatment induced strong cancer-killing effects in all cell lines, according to the results. The researchers also gave the treatment to about ten mice to look for toxins in their blood after treatment, and they found none five to 30 minutes after injection.
The researchers then injected HB21(Fv)-PE40 into the breast ducts of two DCIS mouse models, MCF7 and SUM225. The treatment was given to MCF7 mice once a week for three weeks. Noninvasive imaging was used to monitor the effectiveness of the treatments. In some of the mice, they also administered the treatment and delivered the HB21 antibody alone into the ducts.
The two models represented all of the classifications for common types of human breast cancer: estrogen and progesterone receptor-positive and human epidermal growth factor receptor 2 (HER2) negative, estrogen, and progesterone receptor-negative and HER2-positive, and estrogen and progesterone receptor-negative and HER2-positive.
Those who received toxin treatment injections in the body had slower tumor growth in the MCF7 model. However, tumors returned after treatment was stopped around day 26. In the model that received treatment through the ducts, however, the tumors vanished within two weeks of finishing two of the three treatments, and no recurrence was detected via imaging even after 61 days.
Pathology exams of the mammary glands were performed on day 32 by two investigators from each group. Tumor cells were found to be absent, and the architecture matched that of normal mammary glands. After 61 days, a similar analysis of the remaining samples revealed invasive tumors in the model that only received HB21, small tumors in those treated in the body cavity, and no tumors in those treated through the ducts.
A pilot experiment with the toxin treatment in the SUM225 model revealed tumor clearance as early as two weeks of treatment, as seen through imaging. There was no recurrence until the experiment was terminated on day 48. In a subsequent experiment, the same dose and a 1/10th dose of the treatment, as well as HB21 antibody alone, were tested in some samples.
The majority of the mammary glands were tumor-free after the full intraductal treatment, with the lower dose producing weaker results. SUM225 tumors were discovered to grow rapidly in the in-duct location. Pathology studies revealed that HB21 antibody alone had little effect on tumor reduction, whereas immunotoxin conjugate treatment had a significant effect.
The treatment was well tolerated, with no toxin or injection-related side effects.
Because most low-grade DCIS will not progress, Sukumar recommends active surveillance and hormone therapy, with larger lesions, often treated more aggressively. "This larger and higher-grade DCIS may be the lesions where intraductal immunotoxin would be most beneficial," she says. The major advantage is that administering the immunotoxin intraductal allows it to reach all cancer lesions in the ductal tree, eliminating even those that are not visible on breast imaging.
"A potential clinical study would look like this," Sukumar says. "A week or two before surgery, researchers may give women a low dose of HB21(Fv)-PE40 through a single duct, then gradually increase the dose to see if any immunotoxin escapes the ducts and affects liver function." They would also examine the ducts after breast removal for changes in tissue and their impact on precancerous lesions.
Guannan Wang, Alok Kumar, Preethi Korangath, Priya Pai, and Kathleen Gabrielson of Johns Hopkins University, Wanjun Ding of Renmin Hospital of Wuhan University in China, and Tapan Bera, Junxia Wei, and Ira Pastan of the National Cancer Institute were study co-authors.
The Janine Goebel Fund and the John Fetting Fund for Breast Cancer Prevention provided funding for this research.