Cervical Tumor Cell Lines Research Articles

Ubiquitous induction of resistance to platinum drugs in human ovarian, cervical, germ-cell and lung carcinoma tumor cells overexpressing isoforms 1 and 2 of dihydrodiol dehydrogenase.

We have recently demonstrated that overexpression of dihydrodiol dehydrogenase (DDH) in human ovarian carcinoma cells (2008/C13*) is associated with cisplatin and carboplatin resistance. Furthermore, we have also elucidated that transfection of parental human ovarian carcinoma cells with a full-length DDH1 cDNA leads to induction of resistance to the platinum drugs. The development of cisplatin resistance in the transfected cells is associated with an increase in DDH enzyme activity. Previous studies have identified several different mechanisms for development of cisplatin resistance, including altered DNA repair capacity, increased GSH-based detoxification, and increased metallothionein content. However, none of these mechanisms has been found to be universally associated with the development of cisplatin resistance in tumor cells from different tissue sources. The present study was undertaken to assess whether overexpression of DDH1 or DDH2 (in human ovarian, cervical, lung and germ-cell tumor cell lines) could specifically induce resistance to the platinum drugs in these cell lines. We demonstrated a ubiquitous association of increased expression of DDH1 or DDH2 (as judged by increased enzyme activity in transfected clones) with development of resistance to cisplatin and carboplatin. Moreover, we also found a lack of cross-resistance to anticancer drugs that have a different mode of action including paclitaxel, vincristine, doxorubicin hydrochloride, and melphalan. Although at present it is not clear how DDH is involved in platinum drug resistance, the identification of this gene as a causal factor in a series of cell lines derived from different tumors with different intracellular compositions indicates the importance of deciphering this hitherto undefined pathway which can produce resistance to platinum drugs.

The relationship between connexins, gap junctions, tissue architecture and tumour invasion, as studied in a novel in vitro model of HPV-16-associated cervical cancer progression.

Disruption of gap junctional intercellular communication (GJIC) and/or connexins (gap junction proteins) is frequently reported in malignant cell lines and tumours. Certain human papillomaviruses (HPV) associated with the development of cancers, especially of the cervix, have previously been reported to downregulate GJIC in vitro. There is also evidence for reduced gap junctions in cervical dysplasia. However, many squamous hyperproliferative conditions, including HPV-induced warts, often show extensive upregulation of certain connexins. The association between HPV and GJIC, and the mechanism and consequence of deregulated GJIC in cervical tumour progression, remains unclear. Therefore, using a variety of nonmalignant and malignant cell lines and an organotypic raft-culture system, we investigated the relationship between HPV, gap junctions and tumour progression. Established cervical tumour cell lines carrying HPV were unable to communicate via gap junctions (when assayed by dye-transfer techniques). This correlated with lack of connexin protein expression, while transfection with connexins 26 or 43 led to functional gap junction membrane plaques. On the other hand, immortal but nonmalignant cell lines that contained episomal or integrated HPV-16, but required feeder-layer and growth-factor support, were consistently well coupled, and expressed multiple connexins at membrane junctions. In vitro selection of feeder-layer and growth-factor-independent variants eventually lead to loss of GJIC, which correlated with loss of membrane and increased cytoplasmic connexin 43 localization. However, this was preceded by loss of differentiation and stromal invasion, as assayed on the organotypic raft-culture model. Using this model, a comparison between noncoupled, well-coupled and connexin-transfected cell lines revealed no firm correlation between GJIC and dysplasia, but GJIC appeared to favour increased stratification. These findings demonstrate that loss of GJIC is frequent, but appears to occur more as a consequence of, rather than being the cause of, epithelial dysplasia, and may be influenced by, but is not directly attributable to, HPV.

Identification of triterpene hydroxycinnamates with in vitro antitumor activity from whole cranberry fruit (Vaccinium macrocarpon).

Bioactivity-guided fractionation of cranberry fruit was used to determine the identity of triterpenoid esters from Vaccinium macrocarpon, which inhibit tumor cell growth and may play a role in cancer prevention. In our previous study, a fraction from whole fruit exhibited tumor cell growth inhibition in vitro. The major components of this fraction were isolated by chromatographic separation of ethyl acetate extracts, purified by semipreparative HPLC, and identified by NMR as cis- (1) and trans- (2) isomers of 3-O-p-hydroxycinnamoyl ursolic acid. These triterpenoid esters have not been previously reported in Vaccinium fruit. Bioassay of the purified triterpene cinnamates in tumor cell lines in vitro showed slightly greater activity of compound 1 in most cell lines, with GI(50) values of approximately 20 microM in MCF-7 breast, ME180 cervical and PC3 prostate tumor cell lines. Quercetin was slightly less active than 1, while cyanidin-3-galactoside exhibited much lower cytotoxicity, with GI(50) greater than 250 microM in all cell lines. Phenylboronic acid (3) was also isolated from the fruit but showed insignificant antitumor activity.

Radiosensitizing and anti-proliferative effects of resveratrol in two human cervical tumor cell lines

Resveratrol is a polyphenol isolated from the skins of grapes that has been shown to significantly alter the cellular physiology of tumor cells, as well as block the process of initiation and progression. At least one mechanism for the intracellular actions of resveratrol involves the suppression of prostaglandin (PG) biosynthesis. The involvement of PGs and other eicosanoids in the development of human cancer is well established. PGs are synthesized from arachidonic acid via the cyclooxygenase pathway and have multiple physiological and pathological functions. In addition, evidence has arisen suggesting that PGs may be implicated in the cytotoxic and/or cytoprotective response of tumor cells to ionizing radiation (IR). As such, we hypothesized that tumor cells may exhibit changes in the cellular response to IR following exposure to resveratrol, a naturally occuring compound that inhibits cyclooxygenase-1 (COX-1) activity. Thus, clonogenic cell survival assays were performed using irradiated HeLa and SiHa cells pretreated with resveratrol prior to IR exposure, and resulted in enhanced tumor cell killing by IR in a dose-dependent manner. Further analysis of COX-1 inhibition indicated that resveratrol pretreatment: (1), inhibited cell division as assayed by growth curves; and (2), induced an early S phase cell cycle checkpoint arrest, as demonstrated by fluorescence-activated cell sorting, as well as bromodeoxyuridine pulse-chase analysis. These results suggest that resveratrol alters both cell cycle progression and the cytotoxic response to IR in two cervical tumor cell lines.

Raf-1 kinase activity predicts for paclitaxel resistance in TP53mut, but not TP53wt human ovarian cancer cells.

We have recently reported that there is a significant Raf-1 kinase dependency of paclitaxel resistance in human cervical tumor cell lines. In light of the possibility that Raf-1 kinase inhibitors could be used to enhance paclitaxel responsiveness in ovarian cancer, we have characterized the Raf-1 kinase dependency of paclitaxel resistance in ovarian cancer cells. The relationship between Raf-1 kinase activity and the sensitivity to clinically relevant paclitaxel concentrations was determined in four ovarian cancer cell lines (CA-OV3, SK-OV3, 2780/WT and OAW42/WT). Furthermore, in recognition that such a drug combination would initially be used in patients whose tumors have recurred following cisplatin/paclitaxel treatment, we also determined the Raf-1 kinase dependency of paclitaxel cytotoxicity in cisplatin resistant variants of two of the ovarian cell lines (2780/CP and OAW42/CP). In the two cell lines (2780/WT and OAW42/WT) that possess a wild-type TP53 (TP53wt), the relationship between Raf-1 kinase activity and paclitaxel resistance was different from that observed in the cervical tumor cell lines. In these cell lines, paclitaxel-induced far more cell killing than would have been predicted from their Raf-1 kinase activity. However, in the ovarian cancer cell lines (CA-OV3, SK-OV3, 2780/CP and OAW42/CP) that have a mutant TP53 (TP53mut), the cytotoxicity induced by 60 nM paclitaxel exhibited the same relationship to Raf-1 kinase activity as previously observed in cervical tumor cell lines. These data suggest that the therapeutic efficacy of paclitaxel in ovarian cancer patient whose tumors have TP53mut might be increased if it is administered in combination with Raf-1 kinase inhibitors, e.g., ISIS 5132.

Differential impact of Raf-1 kinase activity on tumor cell resistance to paclitaxel and docetaxel.

Docetaxel (Taxotere) is becoming increasingly important in the treatment of many tumor sites and is unusually active in tumors that are resistant to the structurally similar taxane, paclitaxel. These data suggest that the processes that confer cellular paclitaxel resistance may have a substantially lower impact upon the cytotoxicity induced by docetaxel. We have recently reported that there is a marked Raf-1 kinase dependency of paclitaxel resistance in human cervical and ovarian tumor cell lines. We therefore characterized the impact that inherent and genetically induced variations in Raf-1 kinase activity have on the docetaxel cytotoxicity in human ovarian and cervical cancer cell lines. Our data suggest that docetaxel cytotoxicity is independent of Raf-1 kinase activity in the cell lines studied and that the lack of cross-resistance between these two taxane compounds may be due to the differential impact that Raf-1 kinase activity has on their cytotoxicity. Should these relationships pertain to the clinical situation, these findings could form the basis for a molecular-based triage of patients to receive docetaxel when response to paclitaxel may be unlikely due to high Raf-1 kinase activity.

Human papilloma virus status and chromosomal imbalances in primary cervical carcinomas and tumour cell lines

Human papilloma virus (HPV) infection is the crucial step in the initiation of cervical carcinomas. In addition, HPV18 has been implicated in tumour progression and adverse clinical outcome. We determined the HPV types in 12 primary cervical carcinomas and 12 cell lines and compared the findings with the comparative genetic hybridisation (CGH) pattern of chromosomal alterations. The most frequent alteration was the deletion at 3p14 followed by the loss of 2q34-q36 along with 3q gain. High risk HPV types were detected in all samples except one primary tumour. In contrast to the normal distribution, HPV18 was present in 75% of cases including all cell lines. The cell lines carried a higher number of genetic alterations and a different CGH pattern for several chromosomes than the primary tumours, despite microdissection. Purely HPV18 positive cases indicated a high incidence of imbalances at specific loci with peaks of the histogram coinciding with known HPV integration sites. The study suggests that HPV infection is associated with a recurrent pattern of chromosomal changes in cervical carcinomas and that the development and progression of these alterations is triggered by integration into the host genome.

Cervical cancer cells induce apoptosis of cytotoxic T lymphocytes.

The goal of immunotherapy is to eliminate tumors by generating tumor-specific cytotoxic T lymphocytes (CTLs) in patients or by adoptively transferring ex vivo-activated CTLs into patients. Clinical trials have shown that tumor-specific CTLs often disappear before tumors are completely eliminated. In this study, the authors show that CTLs specific for cervical tumor cells undergo apoptosis after they are co-cultured with cervical tumor cells. The established cervical tumor cell lines and cervical cancer tissues express CD95 (Fas/Apo-1) ligand. The tumor cell-induced T-cell apoptosis can be blocked by an inhibitory anti-CD95 (APO-1/Fas) antibody, indicating that tumor cells induce apoptosis of CTLs through CD95-CD95 ligand interaction. Addition of interleukin-2 (IL-2) and IL-7 into the culture rescues the CTL from tumor cell-induced apoptosis. The rescued T cells retain their full antitumor cytotoxicity. These data suggest that human cervical tumor cells might actively down-regulate a cellular immune response by inducing apoptosis of specific T cells during immunotherapy. Local use of IL-2 and IL-7 as adjuvants may promote survival of the CTL and, thus, enhance the efficacy of immunotherapy.

Growth inhibition of cervical tumor cells by antisense oligodeoxynucleotides directed to the human papillomavirus type 16 E6 gene.

Human papillomavirus type 16 (HPV-16) is the HPV type most frequently associated with cervical carcinomas. Based on our previous research with anti-HPV ribozymes, we developed a 16-nucleotide antisense oligodeoxynucleotide (AntiE6) able to direct RNase H activity on full-length HPV-16 E6/E7 mRNA. Although the precise mechanism is not completely understood, addition of 50 microM AntiE6 oligodeoxynucleotide in sterile water caused a significant decrease in the growth rate of CaSki and QGU cervical tumor cell lines. In contrast, addition of a mismatched mutant oligodeoxynucleotide (M7) did not affect cell growth after 72 hours. Treatment with AntiE6 resulted in down-regulation of E6/E7 mRNA and an increase in p53 levels in QGU cells. AntiE6 was also able to (>70%) inhibit significantly growth of transplanted cervical tumors in nude mice after 2 weeks treatment using constant delivery by osmotic pumps. These results indicate that the AntiE6 antisense oligodeoxynucleotides can act as a therapeutic agent against cervical carcinomas.

Incorporation of an 125 I-Labeled Hexa-Iodinated Diglyceride Analog into Low-Density Lipoprotein and High Specific Uptake by Cells of Cervical Carcinoma Cell Lines

The feasibility of using low-density lipoprotein (LDL) to deliver cytotoxic drugs to tumor cells has been explored since the 1980s, when cells of a number of cancer cell lines were found to have higher LDL receptor activity than normal cells. Such differential uptake between tumor and normal cells may provide a unique opportunity to use LDL as a tumor-specific carrier of radiopharmaceuticals for the clinical management of cancer. In this study, an (125)I-labeled hexa-iodinated diglyceride analog, 1, 3-dihydroxypropan-2-one 1,3-diiopanoate (DPIP), was synthesized and incorporated into LDL using a fusion technique. It was found that approximately 500 [(125)I] DPIP molecules were incorporated into each LDL particle. Cells of three human cervical tumor cell lines, HeLa, SiHa and C-33A, were used to examine the cellular uptake of the [(125)I]DPIP-LDL conjugate. It was shown that the [(125)I]DPIP-LDL conjugate was specifically bound to and taken up by cervical tumor cells through an LDL receptor-mediated endocytosis pathway. The results suggest that LDL may be a selective carrier for delivering hydrophobic radiopharmaceuticals to cancer cells and particularly for the diagnosis of cervical tumors.

Adenoviral delivery of B7-1 (CD80) increases the immunogenicity of human ovarian and cervical carcinoma cells.

The majority of tumour cells do not express immune costimulatory molecules and this may account for their inability to stimulate directly an antitumour T cell response. Here we report on the construction of a recombinant E1/E3-deleted adenovirus encoding the human B7-1 costimulatory molecule. We explored the use of this vector for gene transfer to a number of human ovarian and cervical tumour cell lines, and to primary ovarian tumour material. Rapid and efficient gene transfer and expression was obtained in the majority of cases using a multiplicity of infection of 30 plaque forming units per cell. B7-1 expression was detectable at the cell surface within 12 h and was still detectable 10 days after infection. The immunogenicity of gene-modified tumour cells was tested in an allogeneic mixed lymphocyte tumour cell culture. Tumour cells expressing B7-1 were found to induce significantly higher levels of T cell proliferation than tumour cells modified with a control adenovirus carrying the beta-galactosidase gene. B7-1-induced T cell proliferation could be blocked by the addition of anti-B7-1 antibodies at the initiation of cocultures. These results support the rationale for use of adenovirally delivered B7-1 for genetic immunotherapy of ovarian and cervical cancer.

The ratio of initial/residual DNA damage predicts intrinsic radiosensitivity in seven cervix carcinoma cell lines.

The single-cell gel electrophoresis (comet) assay was used to measure radiation-produced DNA double-strand breaks (dsbs) in a series of seven cervical tumour cell lines (ME180, HT3, C33A, C41, SiHa, MS751 and CaSki). The proportion of DNA dsbs was measured immediately after radiation treatment (initial damage) and 16 h later after incubation at 37 degrees C (residual damage). Linear dose-response curves were seen for initial (slopes 0.23-0.66) and residual (slopes 0.16-0.87) DNA dsbs. Neither of the slopes of the linear regression analysis on the initial and on the residual DNA dsbs dose-response curves (range 0-80 Gy) correlated with SF2 (surviving fraction at 2 Gy) measured after high- (HDR) or low-dose-rate (LDR) irradiation. An association was evident between SF2 after HDR and LDR irradiation and the ratio of the absolute level of initial and residual damage after a single dose of 60 Gy. However, a significant correlation was found between HDR (r= -0.78, P = 0.04) and LDR (r = -0.86, P = 0.03) SF2 values and the ratio of the slopes of the initial and residual DNA dsbs dose-response curves (range 0.47-0.99), representing the fraction of DNA damage remaining. These results indicate that the neutral comet assay can be used to predict radiosensitivity of cervical tumour cell lines by assessing the ratio of initial and residual DNA dsbs.

Effect of cisplatin on the clinically relevant radiosensitivity of human cervical carcinoma cell lines

To evaluate the effect of clinically relevant levels of cisplatin on the radiosensitivity of human cervical tumor cells, and to estimate what changes in local control rates might be expected to accrue from the concomitant use of cisplatin during fractionated radiotherapy. The effects of concomitant cisplatin (1 microgram/ml, a typical intratumor concentration) on the clinically relevant radiosensitivity, i.e., surviving fraction after 2 G (SF2) values, was determined in 19 cloned human cervical tumor cell lines. These early passage cell lines had SF2 values ranging from 0.26 to 0.87. The concomitant administration of cisplatin reduced the clinically relevant radiosensitivity in the majority (11 out of 19) of the human tumor cell lines investigated. In only 4 out of 19 was any radiosensitization observed, and in 4 out of 19 cell lines there was no significant change in radiosensitivity. However, the sum of the independent cell killing by radiation and cisplatin, was approximately twofold higher than after radiation alone. There was no apparent dependence of the cisplatin-induced changes in SF2 values upon the level of cell killing by cisplatin. However, there is a suggestion that concomitant cisplatin administration may have a differential effect in inherently radiosensitive and resistant human tumor cell lines. Our data suggest that concomitant cisplatin/radiotherapy regimens may result in a higher level of local tumor control, but primarily through additive toxicity and not through radiosensitization. Future improvements in local tumor control may, thus, be derived by increasing the total dose of cisplatin.

Tamoxifen Regulation of Ectocervical Cell Differentiation

To determine the effects of tamoxifen on the growth and differentiation of normal human cervical cells and compare those effects with those of a synthetic estrogen, diethylstilbestrol (DES). In addition, the effects of these compounds on immortalized cervical cells and cervical tumor cells were ascertained. Growth curves were used to determine the effects on cell proliferation. The expression of several proteins was used to determine the effects on cell differentiation. Binding assays and Western analysis were used to determine estrogen receptor levels. Both tamoxifen and DES inhibited the proliferation of normal cervical cells. This growth inhibition was coincident with an increase in cell differentiation as determined by cornified envelope formation. The increase in envelope number was not accompanied by an increase in involucrin or cornifin, two protein precursors of the envelope. The activity of transglutaminase, which enzymatically incorporates precursor proteins into the envelope, was not stimulated following treatment. Diethylstilbestrol did not alter the growth or differentiation of the human papillomavirus 16-immortalized cell line ECE16-1 or any of the cervical tumor cell lines. Of all the immortalized or cancer cell lines, only Caski cells were growth inhibited by tamoxifen. Normal ectocervical epithelial cells and Caski cells expressed the high-affinity 56-kDa estrogen receptor, but 3H-estradiol binding was not detected in cell extracts from either ME180 or ECE16-1 cells. Nevertheless, extracts from ME180 cells contained an immunoreactive band at the appropriate molecular weight for the estrogen receptor. These results suggest that tamoxifen and DES act similarly in normal cervical cells to promote cervical cell differentiation. However, because Caski cell growth was inhibited by tamoxifen and not DES, the effects of tamoxifen in these cells may be mediated by non-estrogen receptor mechanisms.

Immunohistochemical analysis of proliferation and differentiation in organotypic cultures of cervical tumor cell lines

Researchers have previously demonstrated that organotypic cultures of cervical tumor cell lines exhibit morphological characteristics similar to the in vivo biopsies from which they were derived (Rader et al., 1990). Both the in vivo biopsy and organotypic culture appeared undifferentiated. We have extended these studies with immunohistochemical analysis using the proliferation and differentiation markers, proliferating cell nuclear antigen (PCNA) and involucrin, respectively, to evaluate in more detail the ability of cervical tumor cell lines to differentiate in organotypic culture. An HPV-immortalized keratinocyte cell line, PE-4, expressed PCNA in the lower half and involucrin in the upper half of the organotypic culture which is consistent with the characteristics of a preneoplastic lesion in vivo. The CC-1 cell line, derived from an invasive squamous cell carcinoma, appeared undifferentiated, but expressed involucrin in the upper half of the organotypic culture. This is the first observation of expression of a differentiation marker in an organotypic culture of a cervical tumor cell line. The other cervical tumor cell lines, SiHa and HeLa, derived from a squamous cell carcinoma, and an adenocarcinoma of the cervix, respectively, did not express detectable levels of involucrin or mucin. All three cervical tumor cell lines, CC-1, SiHa and HeLa, expressed PCNA throughout their entire thickness. The majority of nuclei in SiHa and HeLa cultures were PCNA-positive, while the CC-1 cell line exhibited a lower growth fraction. The different proliferation and differentiation characteristics, representing a preneoplastic lesion (PE-4), a low grade (CC-1) and high grade (SiHa and HeLa) tumors, demonstrate that organotypic cultures of these cell lines provide an in vitro model system to study radiation and drug effects on tumors.

HUMAN LUNG, BLADDER AND HEAD AND NECK TUMORS AS COMPARED TO THEIR ADJACENT NORMAL-TISSUES HAVE ELEVATED AP-1 ACTIVITY AND RECOGNIZE SEQUENCE ELEMENTS OF HIV-1 LTR

We have previously reported the specific binding of nuclear factor AP-1 isolated from human breast MDA MB 468 and HeLa cervical tumor cell lines to oligonucleotides complementary to three newly elucidated sequences within the HIV-1 LTR. These synthesized oligonucleotides, which bear high homology to the AP-1 recognition sequence, were used in the present study in gel retardation assays together with unfractionated nuclear protein extracts from human lung, bladder and head and neck tumors and adjacent normal tissue to study the role of the AP-1 protein in the regulation of HIV-1 expression. We found increased binding of AP-1 to these oligonucleotides in 9/12 lung tumors, 9/14 bladder tumors and 7/7 head and neck tumors as compared to adjacent normal tissues. This confirms previous results obtained when using MDA MB 468 and HeLa nuclear protein extracts. These results indicate that, AP-1 could be contributing to the HIV-1 transcriptional regulation through its interaction with the AP-I binding sites of HIV-I LTR.

Oncolytic Activity of NK Cells against SW-756 Squamous Cervical Carcinoma Cell Line: Role of Interferons α and γ and CD54 Adhesion Molecule in Oncolysis

We investigated the sensitivity of a cervical tumor cell line SW-756 to lysis by peripheral blood mononuclear cells (MNC), natural killer (NK) cells, and major histocompatibility complex (MHC)-nonrestricted (MHC-NR) T cells from cervical cancer patients and normal donors. We found that SW-756 was resistant to lysis mediated by naive (unstimulated) MNC and MHC-NR T cells, but sensitive to lysis by naive NK cells. However, the cytotoxic function of MNC could be activated with interleukin-2 (IL-2) and interferon (IFN) α or γ. Although IFNs were effective in enhancement of effector cell cytotoxicity and inhibited proliferation of cervical tumor cells, they also exerted an adverse effect on cytotoxicity; specifically, pretreatment of SW-756 cells with IFNs significantly decreased their susceptibility to lysis by effector cells. Analysis of surface phenotype of SW-756 cells after treatment with IFNs showed up-regulation of expression of HLA class I determinants, the phenomenon that may be responsible for decreased sensitivity of this tumor to MHC-NR NK cells. The studies on the involvement of CD54 adhesion molecule in cytotoxic functions indicated that expression of this molecule on effector cells (but not on target cells) was important for cytotoxicity against SW-756 tumor cells. The therapeutic implication of these studies for patients with cervical cancer is discussed.

Modulation of P53 expression in human cervical tumor cell lines using sense and antisense retroviral constructs

Modulation of P53 expression in human cervical tumor cell lines using sense and antisense retroviral constructs

Normal human chromosome 11 suppresses tumorigenicity of human cervical tumor cell line SiHa.

We examined the ability of human chromosome 11 derived from normal fibroblast cells to suppress the tumorigenicity of SiHa cells, a human cervical tumor cell line. Using DNA transfection, the human chromosome was tagged with a selectable marker (the pSV2neo gene, which encodes resistance to the antibiotic G418), transferred to mouse A9 cells by cell hybridization and microcell transfer techniques, and then transferred to SiHa cells by microcell transfer. These procedures resulted in the appearance of 15 independent, G418-resistant clones, 5 of which had one or two extra copies of an intact human chromosome 11. In situ chromosomal hybridization of these clones with the pSV2neo plasmid revealed the presence of a neo-tagged human chromosome 11 in all of the five SiHa-microcell hybrids. Two SiHa-microcell hybrids that contained a single copy of neo-tagged human chromosome 12 were also isolated by the same methods. The tumorigenicities of SiHa clones with one or two extra copies of chromosome 11 (SiHa-11) were suppressed; four of the five SiHa-11 clones formed no tumors in nude mice, whereas both parental SiHa cells and SiHa cells with an extra chromosome 12 formed tumors within 30 d. One SiHa-11 cell clone formed a single tumor 90 d after injection. This rare tumor had lost one copy of chromosome 11 and rapidly formed tumors when reinjected. These results indicate that the introduction of a single copy of normal human chromosome 11, but not chromosome 12, suppresses the tumorigenicity of SiHa cells, indicating the presence on human chromosome 11 of a putative tumor-suppressor gene (or genes) for human cervical tumors.

Production of Pregnancy-Associated Plasma Protein-A (PAPP-A) by Cultured Tumour Granulosa Cells

Ten ovarian and 2 cervical tumour cell lines were analysed for the production of pregnancy-associated proteins. Pregnancy-associated plasma protein-A (PAPP-A) was detected by radioimmunoassay in culture media of 2 out of 4 (50%) tumour granulosa cell lines (mean = 104 microIU/10(5) cells/24 h) but not in any ovarian (n = 6) or cervical (n = 2) tumour cell lines. By contrast, human chorionic gonadotrophin (hCG), pregnancy specific beta 1-glycoprotein and alpha-fetoprotein (AFP) were not detected in any of the PAPP-A positive media. Only two cell lines produced hCG (58.5 and 25.5 mIU/10(5) cells/24 h). No AFP was produced by any of these 12 cell lines, whereas placental protein 5 was positive in 7. None of these proteins were detected in the culture media of 4 cell lines. In vitro derived PAPP-A was immunologically indistinguishable from either pregnancy or ovarian follicular PAPP-A. All PAPP-A species interacted reversibly with immobilised heparin and were determined by molecular sieve chromatography to have an apparent molecular weight of 820,000 daltons. Cultured tumour granulosa cells specifically synthesised and secreted a large protein which was immunologically and physicochemically indistinguishable from in vivo (pregnancy and ovarian follicular) derived PAPP-A.