Somatosensory cortex of macaque monkeys is designed for opposable thumb.

The evolution of opposable thumb has enabled fine grasping ability and precision grip, therefore the ability to finely manipulate the objects and refined tool use. Since tactile inputs to an opposable thumb are often spatially and temporally out of sync with inputs from the fingers, we hypothesized that inputs from the opposable thumb would be processed in an independent module in the primary somatosensory cortex (area 3b). Here we show that in area 3b of macaque monkeys, most neurons in the thumb representation do not respond to tactile stimulation of other digits and receive few intrinsic cortical inputs from other digits. However, neurons in the representations of other 4 digits respond to touch on any of the 4 digits and interconnect significantly more. The thumb inputs are thus processed in an independent module, whereas there is a significantly more interdigital information exchange between the other digits. This cortical organization reflects behavioral use of a hand with an opposable thumb.

Large-scale reorganization of the somatosensory cortex following spinal cord injuries is due to brainstem plasticity.

Adult mammalian brains undergo reorganization following deafferentations due to peripheral nerve, cortical or spinal cord injuries. The largest extent of cortical reorganization is seen in area 3b of the somatosensory cortex of monkeys with chronic transection of the dorsal roots or dorsal columns of the spinal cord. These injuries cause expansion of intact face inputs into the deafferented hand cortex, resulting in a change of representational boundaries by more than 7 mm. Here we show that large-scale reorganization in area 3b following spinal cord injuries is due to changes at the level of the brainstem nuclei and not due to cortical mechanisms. Selective inactivation of the reorganized cuneate nucleus of the brainstem eliminates observed face expansion in area 3b. Thus, the substrate for the observed expanded face representation in area 3b lies in the cuneate nucleus.

Measurement of residual breast cancer burden to predict survival after neoadjuvant chemotherapy.

PURPOSE: To measure residual disease after neoadjuvant chemotherapy in order to improve the prognostic information that can be obtained from evaluating pathologic response. PATIENTS AND METHODS: Pathologic slides and reports were reviewed from 382 patients in two different treatment cohorts: sequential paclitaxel (T) then fluorouracil, doxorubicin, and cyclophosphamide (FAC) in 241 patients; and a single regimen of FAC in 141 patients. Residual cancer burden (RCB) was calculated as a continuous index combining pathologic measurements of primary tumor (size and cellularity) and nodal metastases (number and size) for prediction of distant relapse-free survival (DRFS) in multivariate Cox regression analyses. RESULTS: RCB was independently prognostic in a multivariate model that included age, pretreatment clinical stage, hormone receptor status, hormone therapy, and pathologic response (pathologic complete response [pCR] v residual disease [RD]; hazard ratio = 2.50; 95% CI 1.70 to 3.69; P < .001). Minimal RD (RCB-I) in 17% of patients carried the same prognosis as pCR (RCB-0). Extensive RD (RCB-III) in 13% of patients was associated with poor prognosis, regardless of hormone receptor status, adjuvant hormone therapy, or pathologic American Joint Committee on Cancer stage of residual disease. The generalizability of RCB for prognosis of distant relapse was confirmed in the FAC-treated validation cohort. CONCLUSION: RCB determined from routine pathologic materials represented the distribution of RD, was a significant predictor of DRFS, and can be used to define categories of near-complete response and chemotherapy resistance.

Microtubule-associated protein tau: a marker of paclitaxel sensitivity in breast cancer.

Breast cancers show variable sensitivity to paclitaxel. There is no diagnostic test to identify tumors that are sensitive to this drug. We used U133A chips to identify genes that are associated with pathologic complete response (pCR) to preoperative paclitaxel-containing chemotherapy in stage I-III breast cancer (n = 82). Tau was the most differentially expressed gene. Tumors with pCR had significantly lower (P < 0.3 x 10(-5)) mRNA expression. Tissue arrays from 122 independent but similarly treated patients were used for validation by immunohistochemistry. Seventy-four percent of pCR cases were tau protein negative; the odds ratio for pCR was 3.7 (95% confidence interval, 1.6-8.6; P = 0.0013). In multivariate analysis, nuclear grade (P < 0.01), age <50 (P = 0.03), and tau-negative status (P = 0.04) were independent predictors of pCR. Small interfering RNA experiments were performed to examine whether down-regulation of tau increases sensitivity to chemotherapy in vitro. Down-regulation of tau increased sensitivity of breast cancer cells to paclitaxel but not to epirubicin. Tubulin polymerization assay was used to assess whether tau modulates binding of paclitaxel to tubulin. Preincubation of tubulin with tau resulted in decreased paclitaxel binding and reduced paclitaxel-induced microtubule polymerization. These data suggest that low tau expression renders microtubules more vulnerable to paclitaxel and makes breast cancer cells hypersensitive to this drug. Low tau expression may be used as a marker to select patients for paclitaxel therapy. Inhibition of tau function might be exploited as a therapeutic strategy to increase sensitivity to paclitaxel.

Pathologic changes in breast cancer following neoadjuvant chemotherapy: implications for the assessment of response.

Neoadjuvant chemotherapy (also known as preoperative or primary chemotherapy) is the treatment of choice for patients with locally advanced breast cancer. One of the main advantages of neoadjuvant chemotherapy is that it allows for assessment of pathologic response to treatment. Clinical and radiologic evaluations of response to neoadjuvant chemotherapy are based on change in tumor size, and the correlation with pathologic response is often inaccurate. Pathologic evaluation of tumor size remains the gold standard for evaluation of residual tumor after chemotherapy. Chemotherapy-induced histomorphologic change is commonly observed in posttreatment resection specimens and can contribute to the less-than-perfect correlation between the clinical assessment of tumor size and the pathologic measurement. Therefore, accurate histologic mapping to the macroscopic and radiologic appearance of the tumor bed is necessary. Cytopathologic changes are also common in residual cancer cells after neoadjuvant chemotherapy and have uncertain clinical relevance. There is a role for the development of new histologic approaches to augment the pathologic and clinical assessment and provide information on the differential response, particularly for tumors in which less than pathologic complete response is achieved.

Breast-conserving surgery after neoadjuvant anthracycline-based chemotherapy for large breast tumors.

BACKGROUND: Randomized trials comparing neoadjuvant versus adjuvant chemotherapy show that primary chemotherapy allows more frequent breast-preserving surgery even though no survival advantage has been demonstrated. The aim of the current study was to determine the predicting factors and the survival impact of breast conservation in patients with large breast tumors treated with neoadjuvant chemotherapy. METHODS: Between January 1987 and December 2001, 594 patients with invasive T2-3 breast carcinoma who were ineligible for breast-conserving surgery (the mean initial tumor diameter was 49 mm) were treated with 3 or 4 courses of an anthracycline-based primary chemotherapy, surgery, and radiotherapy. Various clinicopathologic factors were tested as possible predicting factors of breast-preserving surgery. Survival analyses were performed to determine the implications of breast-conserving surgery on outcome. RESULTS: After primary chemotherapy, 287 (48%) patients were eligible for breast-conserving surgery and 307 patients underwent a mastectomy. Initial tumor diameter > 5 cm, low histologic grade, lobular histology, and multicentricity were independent predicting factors of breast conservation ineligibility in the multivariate analysis (logistic regression). In the univariate survival analysis, a failure of breast-preserving surgery was associated with a poor outcome. Local disease recurrence-free survival rates were similar in patients treated with lumpectomy and mastectomy. CONCLUSIONS: The results reported in the current study suggested that initial diameter, histologic type and grade, and multicentricity are potential prechemotherapy predicting factors of breast conservation. When carefully selected, patients treated with breast conservation had a risk of local disease recurrence similar to the risk of chest wall disease recurrence after mastectomy.

Change in tumor cellularity of breast carcinoma after neoadjuvant chemotherapy as a variable in the pathologic assessment of response.

BACKGROUND: Complete pathologic response of breast carcinoma to neoadjuvant chemotherapy is a well defined outcome that correlates with prolonged survival. Categorization of incomplete response depends on accurate measurement of residual tumor size but is complicated by the variable histopathologic changes that occur within the tumor bed. In the current study, the authors investigated the contribution of assessing tumor cellularity in the pathologic evaluation of response to chemotherapy. METHODS: The slides from diagnostic core needle biopsy and the subsequent matched resection specimens were examined in 240 patients with breast carcinoma: 120 "treated" patients who received neoadjuvant chemotherapy and 120 "control" patients who received primary surgical management within a few weeks of diagnosis. Clinical response and residual tumor size were evaluated in 108 treated patients who completed a clinical trial with paclitaxel and then received combined 5-fluorouracil, doxorubicin, and cyclophosphamide chemotherapy. Tumor cellularity was assessed from hematoxylin and eosin-stained tissue sections as the percentage of tumor area that contained invasive carcinoma. RESULTS: After neoadjuvant chemotherapy, tumor cellularity decreased from a median of 40% in core needle biopsy to 10% in resection specimens (P<0.01; Wilcoxon signed rank test). The cellularity of core needle biopsy (median, 30%) tended to underestimate the cellularity of resection specimens (median, 40%) in the control group (P<0.01). Changes in cellularity varied within each clinical response category, particularly partial response and minor response. The greatest reduction was observed in the cellularity of residual primary tumors that measured < or =1 cm (pathologic T1a [pT1a] and pT1b tumors), but changes in cellularity varied in the pT1, pT2, and pT3 residual tumor categories. The shape of the distribution of tumor size, expressed as the greatest dimension in cm, was similar in the control group and the treatment group (excluding complete pathologic response); however, when residual tumor size and cellularity were combined, the distribution of pathologic response shifted left (toward complete response) with a steep decline, suggesting that many tumors had a large reduction in cellularity but little change in the tumor size. CONCLUSIONS: Cellularity of the tumor mass was reduced significantly by neoadjuvant chemotherapy, and the change varied widely in different categories of clinical response. Although residual tumors measuring < or =1 cm in greatest dimension had the most reduction in tumor cellularity, there was broad variability for all residual tumor groups (pT1-pT3). The frequency distribution of residual tumor size was altered markedly by the inclusion of tumor cellularity, indicating that the product of pathologic size and tumor cellularity may provide more accurate pathologic response information than tumor size alone.