A possible game-changer in Breast Cancer Prognosis: Cathepsin D

 

One of the most common forms of cancer that affects women and people assigned female at birth (AFAB), is Breast Cancer. This happens when cancerous cells in the breast multiply and become tumors. 80 percent of Breast Cancer cases are said to be invasive, that is, the tumor could spread from your breast to other surrounding parts of your body. Breast cancer typically affects women aged 50 and older, but it can also affect women and people AFAB who are younger than 50. After skin cancer, breast cancer is the most commonly diagnosed cancer in women. Despite being one of the most extensive forms of cancer, breast cancer survival rates have been actively increasing. The number of people dying due to breast cancer is steadily going down. This has been possible due to the widespread support for breast cancer awareness and research. Advances in screening of breast cancer allows healthcare professionals to diagnose breast cancer earlier.

Certain prognostic factors of breast cancer also allow healthcare professionals to estimate the chance of recovery or chances of recurrence of the cancer. A prognostic factor can be described as a situation or condition, or a characteristic of a patient, that can be used to estimate the chance of recovery from a disease or the chance of the disease recurring (coming back). Cathepsin D, an estrogen-induced, lysosomal protease, could possibly serve as one such prognostic factor. For this study, frozen tissue specimens from 397 patients (among which 199 patients had the node-negative disease and 198 had the node-positive disease) were used. 

Fig 1. Cathepsin D

Levels of Cathepsin D in the 397 primary breast tumor specimen was measured using semi-quantitative Western Blot Procedure. Somewhat higher levels of mature cathepsin D were found in breast tumors that had metastasized to lymph nodes. This may suggest that cathepsin D is important for the malignant metastatic potential of breast cancer cells. In patients with node-negative disease, those with higher levels of cathepsin D had statistically shorter disease-free and overall survival than those with lower levels of the protein. 

Another marker of aggressiveness in breast tumors is ploidy (DNA content): tumors with aneuploid DNA, as measured by flow cytometry, have a higher probability of relapse. High levels of cathepsin D were found more often in aneuploid than in diploid tumors (41 percent vs. 21 percent), and among aneuploid tumors, higher levels of cathepsin D identified patients at extreme risk of recurrence.

For disease-free survival, cathepsin D status was predictive of outcome primarily among those with aneuploid tumors; the actuarial five-year recurrence rates of aneuploid tumors were 60 percent among women with high levels of cathepsin D and 29 percent among those with low levels, as compared with 22 percent for all diploid tumors. We conclude that cathepsin D may be an independent predictor of early recurrence and death in node-negative breast cancer.

REFERENCES:

• Tandon AK, Clark GM, Chamness GC, Chirgwin JM, McGuire WL. Cathepsin D and Prognosis in Breast Cancer. New England Journal of Medicine. 1990 Feb;322(5):297–302.

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