MRI-based 3D pelvic autonomous innervation: a first step towards image-guided pelvic surgery.

OBJECTIVE: To analyse pelvic autonomous innervation with magnetic resonance imaging (MRI) in comparison with anatomical macroscopic dissection on cadavers. MATERIAL AND METHODS: Pelvic MRI was performed in eight adult human cadavers (five men and three women) using a total of four sequences each: T1, T1 fat saturation, T2, diffusion weighed. Images were analysed with segmentation software in order to extract nervous tissue. Key height points of the pelvis autonomous innervation were located in every specimen. Standardised pelvis dissections were then performed. Distances between the same key points and the three anatomical references forming a coordinate system were measured on MRIs and dissections. Concordance (Lin's concordance correlation coefficient) between MRI and dissection was calculated. RESULTS: MRI acquisition allowed an adequate visualization of the autonomous innervation. Comparison between 3D MRI images and dissection showed concordant pictures. The statistical analysis showed a mean difference of less than 1 cm between MRI and dissection measures and a correct concordance correlation coefficient on at least two coordinates for each point. CONCLUSION: Our acquisition and post-processing method demonstrated that MRI is suitable for detection of autonomous pelvic innervations and can offer a preoperative nerve cartography. KEY POINTS: • Nerve preservation is a hot topic in pelvic surgery • High resolution MRI can show distal peripheral nerves • Anatomo-radiological comparison shows good correlation between MRI and dissection • 3D reconstructions of pelvic innervation were obtained with an original method • This is a first step towards image-guided pelvic surgery.

Is low tie ligation truly reproducible in colorectal cancer surgery? Anatomical study of the inferior mesenteric artery division branches.

AIM: Curative surgery is the standard treatment for colorectal cancer. The ligation level of the inferior mesenteric artery (IMA) is still debated, as neither low tie (LT) nor high tie ligation (HT) has shown any benefit on the patients' overall survival. We examined whether LT is standardizable and easily reproducible from an anatomical point of view. METHOD: One hundred CT angiographies of healthy patients were analysed for the anatomy of the IMA and its division branches: left colic artery (LCA), sigmoid arteries trunk and superior rectal artery. Data analysed comprised angles between the IMA and the aorta, diameters of the IMA and its branches, repartition of the branches and distances between the origin of the branches and the origin of the IMA. RESULTS: IMA anatomy showed no variation. In contrast, its division branches showed important variability in terms of distance to the origin and repartition: in 19.9% of the patients, the IMA directly splits into three branches, and in 17.6% of the patients, the LCA originated at more than 5 cm from the origin of the IMA. These frequent variations led us to assume that the standardization of LT is very difficult in a context of neoplasm, where the quality of the lymphadenectomy is fundamental. CONCLUSION: The division branches of the IMA are extremely subject to interindividual variations, making it difficult if not impossible to reproduce identically a surgical procedure based on their anatomy. HT appears to us as the only relevant procedure for colorectal cancer.

Study of the cytolethal distending toxin (CDT)-activated cell cycle checkpoint. Involvement of the CHK2 kinase.

The bacterial cytolethal distending toxin (CDT) triggers a G2/M cell cycle arrest in eukaryotic cells by inhibiting the CDC25C phosphatase-dependent CDK1 dephosphorylation and activation. We report that upon CDT treatment CDC25C is fully sequestered in the cytoplasmic compartment, an effect that is reminiscent of DNA damage-dependent checkpoint activation. We show that the checkpoint kinase CHK2, an upstream regulator of CDC25C, is phosphorylated and activated after CDT treatment. In contrast to what is observed with other DNA damaging agents, we demonstrate that the activation of CHK2 can only take place during S-phase. Use of wortmannin and caffeine suggests that this effect is not dependent on ATM but rather on another as yet unidentified PI3 kinase family member. These results confirm that the CDT is therefore responsible for specific genomic injuries that block cell proliferation by activating a cell cycle checkpoint.

Study of the cytolethal distending toxin-induced cell cycle arrest in HeLa cells: involvement of the CDC25 phosphatase.

HeLa cells exposed to Escherichia coli cytolethal distending toxins (CDT) arrest their cell cycle at the G2/M transition. We have shown previously that in these cells the CDK1/cyclin B complex is inactive and can be reactivated in vitro using recombinant CDC25 phosphatase. Here we have investigated in vivo the effects of CDC25 on this cell cycle checkpoint. We report that overexpression of CDC25B or CDC25C overrides an established CDT-induced G2 cell cycle arrest and leads the cells to accumulate in an abnormal mitotic stage with condensed chromatin and high CDK1 activity. This effect can be counteracted by coexpression of the WEE1 kinase. In contrast, overexpression of CDC25B or C prior to CDT treatment prevents G2 arrest and allows most of the cells to progress through mitosis with only a low percentage of cells arrested in abnormal mitosis. The implications of these results on the biochemical nature of the CDT-induced cell cycle arrest are discussed.

p53 mutations occur in aggressive breast cancer.

Using a polymerase chain reaction-single strand conformation polymorphism approach we analyzed 96 human primary breast tumors for the presence of mutations in exons 2, 5, 6, 7, 8, and 9 of the p53 gene. These exons have been shown to comprise highly conserved sequences and the portion including exons 5 through 9 is believed to be the target for over 90% of the acquired mutations in human cancer. Eighteen tumors of the 96 (18.7%) tested showed reproducibly a variant band indicative of a mutation. Most (15 tumors) of the mutations were single nucleotide substitutions and G:C to A:T transitions were prevalent (6 tumors), G:C to T:A transversions came next (4 tumors), and guanines were always on the nontranscribed strand. Concomitant loss of the wild type allele and mutation of the other copy was observed in only 3 of 18 mutated cases; this is consistent with the heterogeneous cellular composition of breast tumors. Furthermore p53 mutations were correlated to estrogen and/or progesterone receptor negative tumors, thus indicating their relationships to aggressive breast cancer. No association could be observed with DNA amplification events in these tumors.

p53 mutations in ovarian cancer: a late event?

Using a combination of polymerase chain reaction and single-strand conformation polymorphism techniques we analyzed 34 ovarian cancer samples (30 primary tumors and four matched metastases) for the presence of mutations in exons 5, 6, 7, 8 and 9 of the p53 gene. Mutations in this portion of the gene are known to lead to the loss of the oncosuppressive potential of p53. Thirty-six percent (11/30) of the ovarian carcinomas tested presented a mutated p53 allele. Mutations were clustered in exons 5 and 7 to the exclusion of the other exons screened. Most mutations (10/11) were point mutations, but no preferential pattern of nucleotide substitution could be observed. In three tumors the mutation of one allele was concomitant with the loss of the wild-type counterpart. Another sample presented both alleles independently mutated. These observations are in agreement with the recessive nature of the p53 mutation. However, analysis of tissue sections from two tumors showed that the portion composed of 100% cancer cells could hold both the mutated and the wild-type form. Moreover analysis of serial sections gave evidence of a heterogeneous cellular content in one of these tumors, suggesting that p53 mutations may, in some cases, occur late during ovarian cancer evolution. It is, moreover, noticeable that, in matched sets of primary tumors and metastases, the same mutation was observed in both tumor samples. Therefore, even as a late event, p53 mutation occurs before metastatic spread.