BIRC5 (survivin): a pejorative prognostic marker in stage II/III breast cancer with no response to neoadjuvant chemotherapy.

PURPOSE: Neoadjuvant systemic therapy (NAC) is currently used in the treatment of stage II/III breast cancer. Pathological complete response as a surrogate endpoint for clinical outcomes is not completely validated for all subgroups of breast cancers. Therefore, there is a need for reliable predictive tests of the most effective treatment. METHODS: We used a combination of predictive clinical, pathological, and gene expression-based markers of response to NAC in a prospective phase II multicentre randomized clinical trial in breast cancer patients, with a long follow-up (8 years). This study concerned the subpopulation of 188 patients with similar levels of pathological response rates to sequential epirubicin/cyclophosphamide and docetaxel to determine predictive marker of pCR and DFS. We used a set of 45 genes selected from high throughput analysis and a standardized RT-qPCR. We analyzed the predictive markers of pathological complete response (pCR) and DFS in the overall population and DFS the subpopulation of 159 patients with no pCR. RESULTS: In the overall population, combining both clinical and genomic variables, large tumor size, low TFF1, and MYBL2 overexpression were significantly associated with pCR. T4 Stage, lymphovascular invasion, negative PR status, histological type, and high values of CCNB1 were associated with DFS. In the no pCR population, only lymphovascular invasion and high values of BIRC5 were associated with DFS. CONCLUSIONS: We confirm the importance of ER-related and proliferation genes in the prediction of pCR in NAC-treated breast cancer patients. Furthermore, we identified BIRC5 (survivin) as a main pejorative prognostic factor in patients with breast cancers with no pCR. These results also open perspective for predictive markers of new targeted therapies.

Estrogen-Receptor, Progesterone-Receptor and HER2 Status Determination in Invasive Breast Cancer. Concordance between Immuno-Histochemistry and MapQuant™ Microarray Based Assay.

BACKGROUND: Hormone receptor status and HER2 status are of critical interest in determining the prognosis of breast cancer patients. Their status is routinely assessed by immunohistochemistry (IHC). However, it is subject to intra-laboratory and inter-laboratory variability. The aim of our study was to compare the estrogen receptor, progesterone receptor and HER2 status as determined by the MapQuant™ test to the routine immuno-histochemical tests in early stage invasive breast cancer in a large comprehensive cancer center. PATIENTS AND METHODS: We retrospectively studied 163 invasive early-stage breast carcinoma with standard IHC status. The genomic status was determined using the MapQuant™ test providing the genomic grade index. RESULTS: We found only 4 tumours out of 161 (2.5%) with discrepant IHC and genomic results concerning ER status. The concordance rate between the two methods was 97.5% and the Cohen's Kappa coefficient was 0.89. Comparison between the MapQuant™ PR status and the PR IHC status gave more discrepancies. The concordance rate between the two methods was 91.4% and the Cohen's Kappa coefficient was 0.74. The HER2 MapQuant™ test was classified as « undetermined ¼ in 2 out of 163 cases (1.2%). One HER2 IHC-negative tumour was found positive with a high HER2 MapQuant™ genomic score. The concordance rate between the two methods was 99.3% and the Cohen's Kappa coefficient was 0.86. CONCLUSION: Our results show that the MapQuant™ assay, based on mRNA expression assay, provides an objective and quantitative assessment of Estrogen receptor, Progesterone receptor and HER2 status in invasive breast cancer.

Identifying trajectory clusters in breast cancer survivors' supportive care needs, psychosocial difficulties, and resources from the completion of primary treatment to 8 months later.

PURPOSE: This study aimed to chart patterns of simultaneous trajectories over 8 months in breast cancer survivors' (BCS) supportive care needs, psychological distress, social support, and posttraumatic growth. Clusters of BCS among these trajectories were identified and characterized. METHODS: Of 426 BCS study participants, 277 (65%) provided full assessments in the last week of primary cancer treatment and 4 and 8 months later. Latent trajectories were obtained using growth mixture modeling for patients who responded to all scores for at least one time point (n = 348). Then, classification of BCS was performed by hierarchical agglomerative clustering on axes derived from a multiple factor analysis of trajectory assignments. Self-esteem, attachment security, and satisfaction with care were assessed at baseline. RESULTS: Four trajectory clusters were identified, including two BCS subgroups (63%) with low needs and low psychological distress. Two others (37%) exhibited high or increasing needs and concerning levels of psychological distress. These latter clusters were characterized by higher insecure attachment, lower satisfaction with care, and either lower education or younger age, and having undergone chemotherapy. CONCLUSION: More than a third of BCS present unfavorable patterns in supportive care needs over 8 months after primary cancer treatment. Identified psychosocial and cancer care characteristics point to targets for enhanced BCS supportive care.

Histological grade concordance between diagnostic core biopsy and corresponding surgical specimen in HR-positive/HER2-negative breast carcinoma.

BACKGROUND: The identification and validation of suitable predictive and prognostic factors are a challenge to improve the treatment scheme selection. Discordances in histological grade can be established between core biopsy and surgical specimens. This is important in HR-positive/HER2-negative subgroup where histological grade identifies patients at high risk and is a strong determinant for treatment scheme. METHODS: A total of 350 consecutive invasive breast carcinoma biopsies were assessed and compared with surgical specimens in Institut Curie, Paris, France. Clinical, radiological and pathological data were recorded. RESULTS: Histological grade concordance rate in the HR+/HER2- group was 75%. A grade underestimation was mainly due to mitotic index misgrading (23%). Large tumours (P<0.05), premenopausal patients (P=0.005) and non-ultrasound-guided biopsies (P=0.04) were risk factors for misgrading. The highest discordance was found in tumours that required chemotherapy (39%, P<0.05), and it was related to an underestimation of histological grade on core biopsies (94%). CONCLUSIONS: Histological grade in HR+/HER2- group is important to identify patients with poor prognosis and start a systemic therapy. Histological grade discordance was correlated with an underestimation of mitotic index and factors probably associated with intratumor heterogeneity (premenopausal status, tumour size and the type of core biopsy performed). But such discordance did not appear to modify the therapeutic decision, because systemic treatment decision-making also integrates other variables. Determining histological grade in core biopsy can be especially important in HR-positive/HER2-negative subgroup where it identifies patients at high risk and is a strong determinant of the treatment scheme.

Extensive pure ductal carcinoma in situ of the breast: identification of predictors of associated infiltrating carcinoma and lymph node metastasis before immediate reconstructive surgery.

AIM: To identify predictors for infiltrating carcinoma and lymph node involvement, before immediate breast reconstructive surgery, in patients with an initial diagnosis of extensive pure ductal carcinoma in situ of the breast (DCIS). PATIENTS AND METHODS: Between January 2000 and December 2009, 241 patients with pure extensive DCIS in preoperative biopsy had underwent mastectomy. Axillary staging (sentinel node and/or axillary dissection) was performed in 92% (n = 221) of patients. Patients with micro-invasive lesions at initial diagnosis, recurrence or contralateral breast cancer were excluded. RESULTS: Respectively 14% and 21% of patients had a final diagnosis of micro-invasive carcinoma (MIC) and invasive ductal carcinoma (IDC). Univariate analysis showed that the following variables at diagnosis were significantly correlated with the presence of either MIC or IDC in the mastectomy specimen: palpable tumor (p = 0.002), high grade DCIS (p = 0.002) and detection of an opacity by mammography (p = 0.019). Axillary lymph node (ALN) involvement was reported in 9% of patients. Univariate analysis suggested that a body mass index higher than 25 (p = 0.007), a palpable tumor (p = 0.012) and the detection of an opacity by mammography (p = 0.044) were associated with an increased rate of ALN involvement. CONCLUSION: Skin-sparing mastectomy and immediate breast reconstruction (IBRS) has become increasingly popular, especially for patients with extended DCIS of the breast. This study confirmed that extended DCIS is associated with a substantial risk of finding MIC or IDC on the surgical specimen but also ALN involvement. Adjuvant systemic treatment and/or radiotherapy could be indicated for some of these patients after the surgery. Patients should be informed of the rate of 1) complications associated to IBRS that will potentially delay the introduction of systemic or local therapy 2) complications associated to radiotherapy after IBRS.

Challenging single- and multi-probesets gene expression signatures of pathological complete response to neoadjuvant chemotherapy in breast cancer: experience of the REMAGUS 02 phase II trial.

This study was designed to identify predictive signatures of pathological complete response (pCR) in breast cancer treated by taxane-based regimen, using clinicopathological variables and transcriptomic data (Affymetrix Hgu133 Plus 2.0 devices). The REMAGUS 02 trial (n = 153,training set) and the publicly available M.D. Anderson data set (n = 133, validation set) were used. A re-sampling method was applied. All predictive models were defined using logistic regression and their classification performances were tested through Area Under the Curve (AUC) estimation. A stable set of 42 probesets (31 genes) differentiate pCR or no pCR samples. Single-or 2-probesets signatures, mainly related to ER pathway, were equally predictive of pCR with AUC greater then 0.80. Models including probesets associated with ESR1, MAPT, CA12 or PIGH presented good classification performances. When clinical variables were entered into the model, only CA12 and PIGH, remained informative (p = 0.05 and p = 0.005) showing that a combination of a few genes provided robust and reliable prediction of pCR.

Prediction of axillary lymph node status in male breast carcinoma.

BACKGROUND: To evaluate whether predictive factors of axillary lymph node metastasis in female breast cancer (BC) are similar in male BC. PATIENTS AND METHODS: From January 1994 to May 2011, we recorded 80 non-metastatic male BC treated at Institut Curie (IC). We analysed the calibration and discrimination performance of two nomograms [IC, Memorian Sloan-Kettering Cancer Center (MSKCC)] originally designed to predict axillary lymph node metastases in female BC. RESULTS: About 55% and 24% of the tumours were pT1 and pT4, respectively. Nearly 46% demonstrated axillary lymph node metastasis. About 99% were oestrogen receptor positive and 94% HER2 negative. Lymph node status was the only significant prognostic factor of overall survival (P = 0.012). The area under curve (AUC) of IC and MSKCC nomograms were 0.66 (95% CI 0.54-0.79) and 0.64 (95% CI 0.52-0.76), respectively. The calibration of these two models was inadequate. CONCLUSIONS: Multi-variate models designed to predict axillary lymph node metastases for female BC were not effective in our male BC series. Our results may be explained by (i) small sample size (ii) different biological determinants influencing axillary metastasis in male BC compared with female BC.

Cost comparison of axillary sentinel lymph node detection and axillary lymphadenectomy in early breast cancer. A national study based on a prospective multi-institutional series of 985 patients 'on behalf of the Group of Surgeons from the French Unicancer Federation'.

BACKGROUND: Our objective was to assess the global cost of the sentinel lymph node detection [axillary sentinel lymph node detection (ASLND)] compared with standard axillary lymphadenectomy [axillary lymph node dissection (ALND)] for early breast cancer patients. PATIENTS AND METHODS: We conducted a prospective, multi-institutional, observational, cost comparative analysis. Cost calculations were realized with the micro-costing method from the diagnosis until 1 month after the last surgery. RESULTS: Eight hundred and thirty nine patients were included in the ASLND group and 146 in the ALND group. The cost generated for a patient with an ASLND, with one preoperative scintigraphy, a combined method for sentinel node detection, an intraoperative pathological analysis without lymphadenectomy, was lower than the cost generated for a patient with lymphadenectomy [€ 2947 (σ = 580) versus € 3331 (σ = 902); P = 0.0001]. CONCLUSION: ASLND, involving expensive techniques, was finally less expensive than ALND. The length of hospital stay was the cost driver of these procedures. The current observational study points the heterogeneous practices for this validated and largely diffused technique. Several technical choices have an impact on the cost of ASLND, as intraoperative analysis allowing to reduce rehospitalization rate for secondary lymphadenectomy or preoperative scintigraphy, suggesting possible savings on hospital resources.

Establishment and characterisation of a new breast cancer xenograft obtained from a woman carrying a germline BRCA2 mutation.

BACKGROUND: The BRCA2 gene is responsible for a high number of hereditary breast and ovarian cancers, and studies of the BRCA2 biological functions are limited by the lack of models that resemble the patient's tumour features. The aim of this study was to establish and characterise a new human breast carcinoma xenograft obtained from a woman carrying a germline BRCA2 mutation. METHODS: A transplantable xenograft was obtained by grafting a breast cancer sample into nude mice. The biological and genetic profiles of the xenograft were compared with that of the patient's tumour using histology, immunohistochemistry (IHC), BRCA2 sequencing, comparative genomic hybridisation (CGH), and qRT-PCR. Tumour response to standard chemotherapies was evaluated. RESULTS: Histological profile identified the tumour as a basal-like triple-negative breast cancer. Targeted BRCA2 DNA sequencing of the xenograft showed the presence of the mutation previously identified in the carrier. Comparative genomic hybridisation array profiles of the primary tumour and the xenograft revealed a high number of similar genetic alterations. The therapeutic assessment of the xenograft showed sensitivity to anthracyclin-based chemotherapy and resistance to docetaxel. The xenograft was also highly sensitive to radiotherapy and cisplatin-based treatments. CONCLUSIONS: This study describes a new human breast cancer xenograft obtained from a BRCA2-mutated patient. This xenograft provides a new model for the pre-clinical drug development and for the exploration of the drug response biological basis.

Disseminated tumor cells and the risk of locoregional recurrence in nonmetastatic breast cancer.

BACKGROUND: In early breast cancer patients, bone marrow (BM)-disseminated tumor cells (DTCs) were associated with distant metastasis and locoregional recurrence. Our aim was to determine whether BM DTC detection could be related to specific locoregional dissemination of cancer cells, according to radiotherapy volumes. PATIENTS AND METHODS: The relationship between locoregional recurrence-free survival (LRFS) and DTC detection was evaluated according to the various locoregional volumes irradiated after surgery. RESULTS: BM DTCs were detected in 94 of 621 stage I-III breast cancer patients (15%) and were not associated with axillary node status. Eighteen patients (2.9%) experienced locoregional recurrence (median follow-up 56 months), of whom eight (44%) were initially BM DTC positive. BM DTC detection was the only prognostic factor for LRFS [P = 0.0005, odds ratio = 5.2 (2.0-13.1), multivariate analysis]. In BM DTC-positive patients, a longer LRFS was observed in those who were given adjuvant hormone therapy (P = 0.03) and radiotherapy to supraclavicular nodes (SCNs)/internal mammary nodes (IMNs) (P = 0.055) (multivariate analysis; interaction test: P = 0.028). CONCLUSIONS: The presence of DTC in BM may be associated with a different pattern of locoregional cancer cell dissemination and influences LRFS. The possible reseeding of the primary cancer area by DTC could be prevented by systemic hormone therapy but also by SCN/IMN irradiation.

High rates of breast conservation for large ductal and lobular invasive carcinomas combining multimodality strategies.

The literature reports low rates of breast conservation after neoadjuvant chemotherapy for operable breast cancers not amenable to initial breast-conserving surgery. This study aims to compare the outcome of lobular vs ductal carcinomas after neoadjuvant chemotherapy. Between 1989 and 1999, 750 patients with clinical stage II/IIIA ductal (672) or lobular (78) invasive breast carcinomas were treated at the Institut Curie with primary anthracycline-based polychemotherapy followed by either breast conservation (surgery and/or radiotherapy) or mastectomy. Median follow-up was 10 years. Clinical response to primary chemotherapy was significantly worse for lobular than for ductal carcinomas (47 vs 60%; P=0.04), but only histological grade remained predictive in multivariate analysis. Breast conservation was high for both ductal and lobular carcinomas (65 and 54%; P=0.07), due, in part, to the use of radiotherapy, either exclusive or preoperative, for respectively 26 and 40% of patients. The lobular type had no adverse effect, neither on locoregional control nor on overall survival, even in the group of patients treated with breast conservation.

Prognosis of women with stage IV breast cancer depends on detection of circulating tumor cells rather than disseminated tumor cells.

BACKGROUND: At metastatic relapse, detection of circulating tumor cells (CTC) in peripheral blood is predictive of poor survival of breast cancer patients. Detection of disseminated tumor cells (DTC) in bone marrow (BM) is an independent prognostic factor in early breast cancer. We evaluated the prognostic value of DTC detection in the BM of metastatic breast cancer patients. MATERIALS AND METHODS: BM aspirates from 138 patients were screened for DTC with the pancytokeratin mAb A45-B/B3, according to the ISHAGE classification. One hundred and ten patients (80%) were enrolled before first-line treatment. Thirty-seven patients were simultaneously screened for CTC in the blood. RESULTS: DTC detection rate in the BM was 59%. DTC were associated with bone metastasis (P = 0.0001), but not with a poorer overall survival. Adverse significant prognostic factors were hormone receptor negativity (P = 0.0004) and more than one line of chemotherapy (P = 0.002). CTC detection in the subgroup of 37 metastatic patients was associated with shorter survival (P = 0.01). CONCLUSIONS: Detection of CTC but not BM DTC had a prognostic significance in stage IV breast cancer patients. CTC in blood are a more reliable and a less invasive tool to evaluate prognostic and monitor tumor response in this metastatic setting.

Vacuum-assisted large-core needle biopsy (VLNB) improves the management of patients with breast microcalcifications - analysis of 1009 cases.

AIMS: To evaluate the surgical management of patients who underwent VLNB for breast microcalcifications. METHODS: This retrospective study compared the histological results and the surgical procedures in two groups of patients, group 1: large-core needle biopsy n=1009, and group 2: surgical biopsy n=270. RESULTS: After VLNB, 54% patients were not operated on after stereotactic large-core needle biopsy, 42% underwent one operation, 4% underwent two operations and 0.2% underwent three operations. No surgery was performed for 95% of benign lesions. Multiples operations were necessary in 12% of patients with malignant lesions of VLNB group compared to 45% in the surgical biopsy group. The rate of underdiagnosis of borderline lesions and ductal carcinomas in situ was 16% by the large-core biopsy technique. CONCLUSION: VLNB constitutes an alternative to surgical biopsy. This procedure avoids surgery for most benign lesions and reduces the number of surgical procedures in malignant lesions.

Are ipsilateral breast tumour invasive recurrences in young (< or =40 years) women more aggressive than their primary tumours?

The characteristics of ipsilateral breast tumour recurrences (IBTRs) relative to those of their primary tumours (PTs) remain scarcely studied. Of 70 young (< or =40 years) premenopausal women with IBTRs, we studied a series of 63 with paired histological data. Median follow-up since IBTR was 10 years. Rates of histological types, grades or hormonal receptors were not significantly different in PTs and in IBTRs. The concordance between IBTRs and their PTs was good for histological types. IBTRs with conserved histological types tended to occur more locally, but not significantly sooner than others. These IBTRs had good concordance for hormone receptors. In discordant cases there were as many losses as appearances of the receptors. The concordance was weak for grades, with equivalent numbers of IBTRs graded lower as higher than their PTs. The 10-year overall survival rate was 70%. Neither the conservation of histological type, location, nor of the two combined were associated with deaths. Early (<2 years) IBTRs, tended to be associated with poorer survival (HR=2.24 (0.92-5.41); P=0.08). IBTRs did not display features of higher aggressiveness than PTs. Neither clinical nor histological definition of a true recurrence could be established other than the conservation of the histological type.

[HRT in post menopausal women and breast cancer at the Institut Curie]. / Traitement hormonal substitutif de la ménopause et cancer du sein à l'Institut Curie entre 1988 et 1999.

Several recent papers have suggested the role of HRT in the development of breast cancers. From the data base of the Institut Curie we compared the clinical characteristics, histoprognosis factors and survival of a cohort of 6737 patients recorded between 1988 and 1999 in which 1482 declared having receive HRT for more than 6 months. Surgical procedure, locoregional recurrence, metastasis, disease free and global survival were compared bet the patient who received an HRT versus the patients who didn't receive this treatment Mammographic diagnosis was more frequent in the HRT group and the age at diagnosis was smaller (p < 10(-4)). Cancers diagnosed in the HRT group were smaller and had a more favourable biologic profile as well as there were more lobular carcinomas and the conservative treatment was more frequent (p < 10(-4)). Mean follow up was 97 months. Recurrence free survival was not different in the two groups but the metastasis free and global survival were better in the HRT group. HRT remained an independent prognostic factor in a multivariate analysis. In western countries the increasing incidence of breast cancer concerns pre as well as post menopausal women. HRT cannot be considered as the only responsible of this augmentation.

HER2 status of bone marrow micrometastasis and their corresponding primary tumours in a pilot study of 27 cases: a possible tool for anti-HER2 therapy management?

Discrepancies have been reported between HER2 status in primary breast cancer and micrometastatic cells in bone marrow. The aim of this study was to assess HER2 gene status in micrometastatic cells in bone marrow and corresponding primary tumour. Micrometastatic cells were detected in bone marrow aspirations in a prospective series of 27 breast cancer patients by immunocytochemistry (pancytokeratin antibody). HER2 status of micrometastatic cells was assessed by fluorescence in situ hybridisation (FISH), respectively in 24 out of 27. Primary tumour HER2 status was assessed by immunohistochemistry (CB11 antibody) and by FISH in 20 out of 27 of the cases. HER2 was amplified or overexpressed in five out of 27 (18.5%) primary tumours and in four out of 27 (15%) micrometastatic cells. In two cases, HER2 was overexpressed and amplified in primary tumour, but not in micrometastatic cells, whereas, in one case, HER2 presented a low amplification rate (six copies) in micrometastatic cells not found in the primary tumour. We demonstrated that negative and positive HER2 status remained, in the majority of the cases, stable between the bone marrow micrometastasis and the primary tumour. Therefore, the efficiency of anti-HER2 adjuvant therapy could be evaluated, in a clinical trial, by sequential detection of HER2-positive micrometastatic cells within the bone marrow, before and after treatment.

Estrogen receptors evolution in neoadjuvant aromatase inhibitor (AI) therapy for breast cancer in elderly women: stability of hormonal receptor expression during treatment.

UNLABELLED: In France, 20% of breast cancers occur in women over the age of 70 and 10% in women over the age of 80. As these women are not included in screening programs, breast cancer is often diagnosed later, at the stage of a large tumor. PURPOSE: To analyze clinical response, possibilities of conservative treatment and course of hormonal receptors in patients receiving neoadjuvant aromatase inhibitor (AI) therapy for at least 6 months. PATIENTS AND METHODS: There were 75 patients, with a mean age of 75 +/- 8 years (range, 58-91 years) received AI for 6 months after the diagnosis of invasive breast cancer with positive hormonal receptors. Clinical and radiologic tumor reduction, the number of conservative treatments and the course of estrogens receptor-labeled cells were determined for each patient. RESULTS: All but 1 of these patients obtained clinical reduction of their tumor. Of these, 86% patients received conservative treatment. In the majority of patients, estrogen receptor (ER) level did not vary between the initial assay and analysis of the operative specimen. DISCUSSION AND CONCLUSION: Aromatase inhibitors are effective as neoadjuvant therapy in ER positive elderly patients with large tumors, as is tamoxifen. Changes in hormone receptor expression during treatment do not predict clinical response. In our experience, neoadjuvant AI therapy should be administered for at least 6 months to optimize clinical response before deciding upon surgery. Discrepancy observed in the literature could be explained by the duration of the treatment.

Breast inflammatory gigantomastia in a context of immune-mediated diseases.

CONTEXT: Localized breast lesions have been described in lupic or diabetic patients. However, the description of breast gigantomastia in women presenting with autoimmune diseases has not been reported. SETTING: The study took place within the Department of Endocrinology and Reproductive Medicine, Necker Hospital, Paris, France. PATIENTS: We describe eight patients with inflammatory gigantomastia, occurring in a context of immune-mediated diseases: myasthenia, chronic arthritis, or thyroiditis. MAIN OUTCOME MEASURES: Together with hormonal, immunological, and breast magnetic resonance imaging (MRI) evaluation, breast histology enabled us to perform immunocytochemical and indirect immunofluorescence studies. Control sera were obtained from patients with (n = 10) and without (n = 7) antinuclear antibodies. RESULTS: Six of the eight patients developed gigantomastia either at puberty or during pregnancy. Neither a hormonal oversecretion nor a specific immunological pattern was observed. All patients except one presented antinuclear antibodies. Histological study revealed a diffuse, stromal hyperplasia and a severe atrophy of the lobules. A rarefaction of adipocytes was also noted, as previously suggested on MRI. There was a perilobular lymphocytic infiltrate made of CD3+ lymphocytes. Study of sera from five of six cases of gigantomastia showed a nuclear immunofluorescence pattern in normal mammary ductal and lobular glandular epithelium, as well as in kidney and intestine epithelial cells. In control sera, a nuclear signal was observed only when antinuclear antibodies were present. CONCLUSIONS: We suggest that breast tissue may be a target tissue in autoimmune diseases, this process being favored by the hormonal milieu. However, the precise mechanism of such association is not individualized. The fact that stromal hyperplasia is the main histological feature justifies the search for the involvement of growth factors in such a process.