Figure 2: Reduced matriptase decreases mammary tumour burden, growth rate, latency and multiplicity.

A prospective cohort of littermate PymT-Mat⁺ mice (N=14) and PymT Mat^hypo mice (N=12) was followed over time. (a) Tumour burden at 145 days. Mice were euthanized and their mammary tumours resected and the total tumour weight was recorded for PymT Mat⁺ mice (closed circles) and PymT-Mat^hypo mice (open circles). Mean values were 2.6 and 1.1, respectively (P<0.002). (b) Mammary tumour growth rate for PymT-Mat⁺ mice (closed circles) and PymT-Mat^hypo mice (open circles). Mean values were 2.9 and 0.7, respectively (P<0.0001). (c) Kaplan–Meier tumour-free survival curves of PymT-Mat⁺ (black line) and PymT-Mat^hypo (dotted line). The median tumour-free survival times were 89 days versus 122 days, respectively (P<0.007), chi-squared test. (d) Total number of glands with lesions at 145 days for PymT- Mat⁺ mice (closed circles) and PymT-Mat^hypo mice (open circles). Mean values were 4.0 and 2.2, respectively (P<0.0001). (e) Representative whole mounts of inguinal mammary glands from 90-day-old virgin female littermates. Normal mammary epithelium in Mat⁺ gland (upper panel), extensive growth of multiple lesions (arrowheads) in PymT-Mat⁺ gland (middle panel) and one small localized lesion (arrowhead) in PymT-Mat^hypo gland (lower panel). LN=lymph node. (f) Total area of lesions in inguinal mammary glands from PymT-Mat⁺ (closed circles) and PymT-Mat^hypo (open circles) (P<0.0001). Mann–Whitney U-test was used in a,b,d and f. Scale bars, 1 mm.