Delivery of a targeted immunotoxin into the breast ducts through nipple openings eliminated all visible and invisible precancerous lesions in lab studies led by researchers at the Johns Hopkins Kimmel Cancer Center† of breast cancer at a very early stage.
A description of the work performed on mice, which the authors say provides a strong preclinical basis for conducting feasibility and safety studies in patients with stage 0 breast cancer, is published in the June 8 issue of the Proceedings of the National Academy of Sciences†
Stage 0 breast cancer, also known as ductal carcinoma in situ (DCIS), is characterized as the presence of abnormal, precancerous cells in milk ducts in the breast, and it affects approximately 69,000 women each year in the United States. Many women undergo breast removal surgery and radiation treatments for these very early cancers, and in some cases receive chemotherapy or hormone therapies, says senior study author Saraswati Sukumar, Ph.D., a Johns Hopkins professor of oncology and pathology.
“In our study, we proposed an alternative treatment where injecting the immunotoxin drug through the duct can lead to the clearance of the DCIS,” says Sukumar. “To our great surprise, the drugs killed every lesion in that breast duct. I had never seen such dramatic results in my life.”
In their study, the researchers first assessed the cell-killing effects of HB21(Fv)-PE40, a targeted immunotoxin, in four cell lines from different molecular subtypes of breast cancer. The toxin consists of HB21, a monoclonal antibody – a protein that can bind to a specific target (in this case, the human transferrin receptor, a carrier protein found in breast cancer). HB21 is fused with PE40, a fragment of a bacterial toxin that stops protein production in the cells and leads to cell death. The results showed that the treatment produced strong cancer-killing effects in all cell lines. The researchers also administered the treatment to about 10 mice to look for toxins circulating in the blood after treatment, and found no toxins five to 30 minutes after injection.
They then injected HB21(Fv)-PE40 into the mammary ducts of two mouse models of DCIS: MCF7 and SUM225. In MCF7 mice, the treatment was given once a week for three weeks. Treatments were monitored with non-invasive imaging. By comparison, they also delivered the treatment inside the body, delivering the HB21 antibody only into the ducts of some mice. The two models represented all 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.
In the MCF7 model, those who received toxin treatment injections into the body had slower tumor growth. However, the tumors recurred after cessation of treatment around day 26. On the other hand, in the channel-receiving model, the tumors disappeared within two weeks of completing two of the three treatments, and no recurrence was detected via imaging even after 61 days.
On day 32, researchers performed pathology examinations of the mammary glands – two from each group. They found that there were no tumor cells and that the architecture was consistent with normal mammary glands. Similar analysis of the remaining samples at 61 days showed invasive tumors in the model receiving HB21 only, small tumors in those treated in the body cavity and no tumors in those receiving the toxin treatment through the ducts.
In the SUM225 model, a pilot experiment with the toxin treatment showed that tumors had already disappeared after two weeks of treatment, as can be seen via imaging. No recurrence was observed until the experiment was terminated on day 48. A second experiment tested the same dose and a 1/10th dose of the treatment, as well as HB21 antibody alone, in some samples. The majority of mammary glands were tumor free after complete intraductal treatment, with weaker effects seen at the lower dose. SUM225 tumors were found to grow aggressively at the site in the canal. Pathology studies showed that HB21 antibody alone had little effect, while immunotoxin conjugate treatment showed a significant effect on tumor reduction.
The treatment was well tolerated, with no side effects from the toxin or injection.
Since most low-grade DCIS will not progress, active monitoring and hormone therapy are recommended, with larger lesions often treated more aggressively, Sukumar says. “These larger and higher quality DCIS may be the lesions where intraductal administration of immunotoxin would be most beneficial,” she says. The major advantage is that administering the immunotoxin via the intraductal route allows to target all cancerous lesions in the ductal tree, even eliminating those not visible by breast imaging.
“A potential clinical trial would look something like this,” Sukumar says. “A week or two before surgery, researchers can give women a low dose of HB21(Fv)-PE40 through a single channel, and use slowly increasing doses to determine whether an immunotoxin escapes the channels into the bloodstream and affects liver function. They would also examine the ducts after removing the breast to look for changes in the tissue and its effect on precancerous lesions.
The study’s co-authors were Guannan Wang, Alok Kumar, Preethi Korangath, Priya Pai and Kathleen Gabrielson of Johns Hopkins, Wanjun Ding of RenMin Hospital of Wuhan University, China, and Tapan Bera, Junxia Wei, and Ira Pastan of the National Cancer Institute. Institute.
The work was supported by the Janine Goebel Fund and the John Fetting Fund for Breast Cancer Prevention.
Proceedings of the National Academy of Sciences
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