Joosten J J A, van Muijen G N P, Wobbes Th, Ruers T J M
Department of Surgery, University Medical Center Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Anticancer Res. 2003 Jan-Feb;23(1A):427-32.
Earlier reports on animal studies showed inhibition of secondary tumor growth and metastases after cryoablation, probably mediated by an inflammatory response. In this study enhancement of this inflammatory response and its possible additive antitumor effect is evaluated in a mouse tumor model.
Mice received two subcutaneously implanted C--26B tumors on, respectively, day 0 (thigh) and day 7 (flank). The thigh tumor was treated by either cryoablation or resection. In addition the animals received a single dose of lipopolysaccharide (LPS) or anti-IL10 together with, or two days after, surgical treatment. The growth of the flank tumor was followed and plasma levels of IL-1 alpha and TNF-alpha were measured.
Compared to excision of the primary tumor, cryosurgery clearly induced inhibition of secondary tumor growth while plasma levels of TNF (0.09) and IL-1 (0.06) were significantly elevated after cryosurgery when compared to excision (TNF 0.0, IL-1 0.03; p < 0.01). Administration of LPS two days after cryosurgery did not lead to extra inhibition of secondary tumor growth, even at high doses. Remarkably, dose--response studies with LPS administered two days after treatment showed a high mortality at a dose of 200 micrograms (75%) in the excision group while mortality in the cryo-treated group was 13% (p < 0.02). Mortality was directly related to cytokine levels that were significantly higher in the excision group (TNF 3.60, IL-1 0.30) when compared to the cryo-treated group (TNF 1.0, IL-10.15; p < 0.01). In contrast, when 25 micrograms LPS was given at the same time as treatment of the primary tumor either by cryosurgery or excision, mortality in the cryo-treated group (85%) was higher than in the excision group (14%, p < 0.05). Again mortality was related to post-treatment cytokine levels which now were significantly higher in the cryo-treated animals (TNF 1.30, IL-10.35) than in animals treated by excision (TNF 0.60, IL-10.10; p < 0.01). Administration of anti IL-10 did not lead to extra tumor growth inhibition.
These experiments confirm the hypothesis that cryosurgery leads to a systemic inflammatory response. This reaction can lead to the inhibition of tumor growth. Administration of LPS after cryosurgery does not lead to an extra anti-tumor response; animals appear to become endotoxin tolerant. Adversely, when LPS is administered together with cryosurgery, the animals are extremely sensitive to LPS. These findings are in accordance with the clinical observation of cryoshock after cryoablation of liver metastases.
早期动物研究报告显示，冷冻消融后可抑制继发性肿瘤生长和转移，这可能是由炎症反应介导的。在本研究中，我们在小鼠肿瘤模型中评估了这种炎症反应的增强及其可能的附加抗肿瘤作用。
小鼠分别在第0天（大腿）和第7天（胁腹）皮下植入两个C-26B肿瘤。大腿肿瘤通过冷冻消融或切除进行治疗。此外，动物在手术治疗时或手术后两天接受单剂量的脂多糖（LPS）或抗IL-10治疗。观察胁腹肿瘤的生长情况，并测量血浆中IL-1α和TNF-α的水平。
与原发性肿瘤切除相比，冷冻手术明显抑制了继发性肿瘤的生长，与切除术后相比，冷冻手术后血浆中TNF（0.09）和IL-1（0.06）水平显著升高（TNF 0.0，IL-1 0.03；p<0.01）。冷冻手术后两天给予LPS，即使是高剂量，也不会导致继发性肿瘤生长的额外抑制。值得注意的是，治疗后两天给予LPS的剂量反应研究显示，切除组在200微克剂量时死亡率很高（75%），而冷冻治疗组的死亡率为13%（p<0.02）。死亡率与细胞因子水平直接相关，切除组的细胞因子水平（TNF 3.60，IL-1 0.30）明显高于冷冻治疗组（TNF 1.0，IL-10.15；p<0.01）。相反，当通过冷冻手术或切除治疗原发性肿瘤时同时给予25微克LPS，冷冻治疗组的死亡率（85%）高于切除组（14%，p<0.05）。同样，死亡率与治疗后的细胞因子水平相关，此时冷冻治疗动物的细胞因子水平（TNF 1.30，IL-10.35）明显高于切除治疗的动物（TNF 0.60，IL-10.10；p<0.01）。给予抗IL-10不会导致肿瘤生长的额外抑制。
这些实验证实了冷冻手术会导致全身炎症反应的假设。这种反应可导致肿瘤生长的抑制。冷冻手术后给予LPS不会导致额外的抗肿瘤反应；动物似乎对内毒素产生耐受。相反，当LPS与冷冻手术同时给予时，动物对LPS极其敏感。这些发现与肝转移瘤冷冻消融后发生冷冻休克的临床观察结果一致。
