Luparello C, Birch M A, Gallagher J A, Burtis W J
Dipartimento di Biologia Cellulare e dello Sviluppo and Centro di Oncobiologia Sperimentale, Universitá di Palermo, Italy.
Carcinogenesis. 1997 Jan;18(1):23-9. doi: 10.1093/carcin/18.1.23.
It has been previously reported that 8701-BC cells, derived from a primary carcinoma of the breast, constitutively express parathyroid hormone (PTH)-related peptide (PTHrP) and PTH/PTHrP receptor (PTH/PTHrP-R) genes, that N-terminal, mid-regional and C-terminal immunoreactive PTHrP can be found in cell conditioned medium and, furthermore, that exogenously added PTHrP (1-34), (67-86) and, to a minor extent, (107-139) are anti-mitogenic but promote Matrigel invasion by this cell line. It has also been reported that PTHrP gene expression is selectively switched on in those 8701-BC clonal lines endowed with a higher proliferation rate and invasive ability in vitro. Here we have first examined the presence of PTH/PTHrP-R transcript in the different 8701-BC clones by PCR and Southern blot analysis. Second, we have studied the growth and invasive response in vitro to PTHrP fragments by some of these clones, i.e. BC-3A, BC-61 and BC-66, selected on the basis of their lower (BC-3A) or higher (BC-1 and BC-66) Matrigel invasion ability and their expression of PTHrP (positive for BC-61 and BC-66) and PTH/PTHrP-R (positive for BC-61). Our data show the existence of clonal heterogeneity for PTH/PTHrP-R mRNA and for the proliferative and invasive responses elicited by treatment with diverse PTHrP fragments. In particular: (i) the sensitivity to PTHrP (1-34) is restricted due to the uneven expression of PTH/PTHrP-R; (ii) BC-3A cells (the less 'aggressive' clone) are resistant to the anti-mitogenic effect of the PTHrP domains and, most noticeably, exhibit a growth-potentiating response to PTHrP (67-86) opposite to that found for both the parental 8701-BC cells and the two other clones; (iii) all PTHrP fragments tested induced the expression of a growth-restraining and invasion-promoting phenotype by BC-61 cells (one of the more 'aggressive' clones). Present data in vitro support the hypothesis that in vivo PTHrP may be a key element in local control of the invasive process during breast carcinoma development and that its role may be, in turn, dependent upon the biological characteristics and the level of malignancy of the target cells within the multiclonal population of a primary tumour.
先前有报道称，源自原发性乳腺癌的8701 - BC细胞组成性表达甲状旁腺激素（PTH）相关肽（PTHrP）和PTH/PTHrP受体（PTH/PTHrP -R）基因，在细胞条件培养基中可检测到N端、中段和C端免疫反应性PTHrP，此外，外源性添加的PTHrP（1 - 34）、（67 - 86）以及少量的（107 - 139）具有抗增殖作用，但可促进该细胞系的基质胶侵袭。也有报道称，在那些体外具有较高增殖率和侵袭能力的8701 - BC克隆系中，PTHrP基因表达被选择性开启。在此，我们首先通过PCR和Southern印迹分析检测了不同8701 - BC克隆中PTH/PTHrP -R转录本的存在情况。其次，我们研究了其中一些克隆，即BC - 3A、BC - 61和BC - 66，基于其较低（BC - 3A）或较高（BC - 1和BC - 66）的基质胶侵袭能力以及它们PTHrP（BC - 61和BC - 66呈阳性）和PTH/PTHrP -R（BC - 61呈阳性）的表达情况，对PTHrP片段的体外生长和侵袭反应。我们的数据显示，PTH/PTHrP -R mRNA以及不同PTHrP片段处理所引发的增殖和侵袭反应存在克隆异质性。具体而言：（i）由于PTH/PTHrP -R表达不均一，对PTHrP（1 - 34）的敏感性受限；（ii）BC - 3A细胞（侵袭性较弱的克隆）对PTHrP结构域的抗增殖作用具有抗性，最显著的是，其对PTHrP（67 - 86）的反应与亲本8701 - BC细胞及其他两个克隆相反，表现为生长促进反应；（iii）所有测试的PTHrP片段均诱导BC - 61细胞（侵袭性较强的克隆之一）表达生长抑制和侵袭促进表型。目前的体外数据支持这样一种假说，即体内PTHrP可能是乳腺癌发生过程中局部侵袭过程控制的关键因素，而其作用可能反过来取决于原发性肿瘤多克隆群体中靶细胞的生物学特性和恶性程度。
