Page 13 - Read Online
P. 13

Page 8 of 18        Cheng et al. J Cancer Metastasis Treat 2021;7:17  https://dx.doi.org/10.20517/2394-4722.2021.27

               Table 1. E  effects on bone parameters in young and mature tumor-naive mice (mean ± SEM) a
                      2
                                     Young (4-week-old)             Mature (15-week-old)  Young vs. Mature
                            Mean (SEM)            P-values         Mean (SEM)  P-values      P-values
                               E ,   E ,   Control   Control   E  0.05   E ,   Control   Control,   E  0.72 mg,
                                     2
                                                                                                  2
                               2
                                                            2
                                                                          2
                        Control 0.05   0.72   vs. E  0.05  vs. E  0.72  mg vs.   Control 0.72   vs. E  0.72  Young vs.   Young vs.
                                             2
                                                                                  2
                                                      2
                               mg   mg    mg      mg       0.72 mg       mg    mg      Mature    Mature
                Proximal tibiae bone density and volume (6 weeks post-pellet)
                aBMD    89.3   151.1   143.9   < 0.0001  < 0.0001  n.s.  99.4   134.3   < 0.0001  n.s.  n.s.
                     2
                (mg/cm )  (2.2)  (2.9)  (6.4)                     (4.8)  (4.5)
                BV/TV (%) 12.5   82.7   91.1   < 0.0001  < 0.0001  n.s.  10.1 (0.9) 59.5   < 0.0001  n.s.  <0.0001
                        (2.0)  (2.7)  (2.4)                              (3.4)
                Bone turnover markers (2 weeks post-pellet; relative to mature control)
                P1NP    1.8 (0.2) 2.4   2.5   0.0401  0.0197  n.s.  1.0 (0.1)  0.8   n.s.  0.0064  < 0.0001
                               (0.2)  (0.3)                              (0.1)
                CTX-1   1.43 (0.1) 1.9   1.5   0.0142  n.s.  n.s.  1.0 (0.2)  1.5   0.0066  0.0166  n.s.
                               (0.1)  (0.1)                              (0.2)
                Bone cells (2 weeks post-pellet)
                N.Ob/BS   33.1   36.1   39.18   n.s.  n.s.  n.s.  27.1 (6.6) 31.4   n.s.  n.s.   n.s.
                (mm)    (0.7)  (2.1)  (4.3)                              (4.2)
                      2
                N.Ob/mm  393.4   765.8   849.2   0.0051  0.0011  n.s.  240.0   528.3   n.s.  n.s.  0.0278
                        (63.0)  (86.3)  (116.1)                   (70.61)  (5.8)
                N.Oc/BS   8.8 (1.1)  9.5   9.3   n.s.  n.s.  n.s.  7.6 (2.4) 8.3   n.s.  n.s.    n.s.
                (mm)           (0.6)  (0.4)                              (1.5)
                N.Oc/mm 2  112.9   202.0   217.4   0.0237  0.0097  n.s.  64.7   170.1   0.0263  n.s.  n.s.
                        (22.7)  (22.9)  (14.6)                    (22.0)  (47.2)
               a                                                                                  2
                P-values determined by1-way ANOVA with Fisher’s LSD test. N.Ob/BS (mm): Osteoblast number per bone surface; N.Ob/mm : number of
                                                                                       2
               osteoblasts lining trabecular bone per tissue area; N.Oc/BS (mm): osteoclast number per bone surface; N.Oc/mm : number of osteoclasts lining
               trabecular bone per tissue area; aBMD: areal bone mineral density; BV/TV: bone volume/total volume; n.s.: not significant.
               Age-related differences in bone resorption in E -treated mice were less evident in these ovary-intact mice.
                                                        2
               While osteoclast number (N.Oc) per bone surface was not changed by E  treatment in mice of either age,
                                                                              2
               N.Oc per bone area increased significantly and similarly in age of both ages, such that there was no
               difference in Oc counts in young vs. mature E  treated mice [Table 1]. Similarly, CTX-1 levels in 0.72 mg E -
                                                      2
                                                                                                         2
               treated mice of both ages were the same [Table 1]. In toto, these data demonstrate that the greater net
               increases in bone in young (vs. mature) mice treated with same E  dose were attributable to higher rates of
                                                                       2
               bone formation, which were positively associated with osteolytic lesion size, but not incidence, in tumor-
               inoculated young (vs. mature) mice supplemented with the same E  (0.72 mg) dose.
                                                                       2

               Assessing dose-dependency of E  effects on bone turnover in tumor-naive vs. progression of
                                             2
               osteolytic ER+ BMET lesions in ER+ tumor cell-inoculated 5-week-old mice
               Because significant E  effects on bone occurred in mice of both ages, bone effects of a range of lower E
                                  2
                                                                                                         2
               doses previously reported to support dose-dependent growth of orthotopic MCF-7 tumors in vivo  were
                                                                                                   [17]
               next assessed in mice of a single age to determine whether an E  dose could be identified that did not
                                                                        2
               significantly alter bone. Remarkably, E -induced increases in total tibial aBMD were identical for all doses,
                                                2
               plateauing 3 weeks after E -pellet placement in 5-week-old mice [Figure 3A]. Other bone parameters
                                       2
               including proximal tibial aBMD or BV/TV, bone turnover markers, and N.Ob or N.Oc were also similarly
               increased in response to the lowest E  dose (0.05 mg) vs. the highest E  dose (0.72 mg) tested, without any
                                                                           2
                                               2
               dose-dependence [Table 1]. Having documented essentially identical bone microenvironment effects over
               this entire range of E  doses known to support in vivo MCF-7 proliferation at orthotopic sites, with evidence
                                 2
               of dose-dependent increases in circulating E  levels across the range of doses [Supplementary Figure 1], the
                                                     2
               effects of this E  dosing regimen on ER+ BMET progression in MCF-7 cell-inoculated mice of the same age
                            2
   8   9   10   11   12   13   14   15   16   17   18